Carburetor Adjustments

Bills86e

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TampaBay, Florida
Water Crafts
Sea Doo 95, XP, SPX, GTX,
SPI, XP, 97 Polaris Hurricane
#1
Two-Stroke Seadoo-PWC

Accurately tuning a PWC carburetor requires a basic understanding of its functions and adhering to a few basic rules. Most importantly, you can only expect the carb to work as well as your engine does; the performance of your carb cannot make up for a weak or worn out engine. Another point to stress here is that you may not be able to achieve maximum performance from your watercraft simply by changing jets in the carb. A mismatch of engine components and or porting may create a carburetion nightmare. The best advise is to use quality parts and service from reputable dealers.

Tune your carbs with a full tank of gas. Why?....if you tuned your ski with 1/4 tank for max rpm, then filled it up and ran it, you could be too lean.With added weight of the fuel,the motor will want more fuel to pull the extra weight and if your tuned for low fuel, it could put you in a lean condition.Simply tune for a full tank,that way you will have plenty of fuel all the time.

To achieve an accurate calibration with a carb, you should adjust the tuneable circuits in the following order:
1. LOW SPEED ADJUSTER -To adjust a smooth idle
2. POP-OFF PRESSURE -Just off idle to 1/4 throttle in conjunction with the low speed jet.
3. LOW SPEED JET -Just off idle to 1/3 throttle.
4. HIGH SPEED JET - 1/3 to 3/4 throttle.
5. HIGH SPEED ADJUSTER -3/4 to wide open throttle.

CHOKE ROD REMOVAL, DUAL CARBURETORS:
If you have the manual choke, the long stainless needle thru your dual carbs linkage nuts, remove the flame arrestor lower plate screws after you remove the mesh, to see the upper linkage, it takes a #2mm allen wrench on the starboard side into the center of the nut hole, is a set screw you must loosen a turn, to unsecure that long stainless needle from the two choke linkage plate nut(s).

The reason for adjusting the circuits in this order is because several circuits contribute to the total fuel delivery of the carb. Changing the low speed jet for example, affects wide open throttle fuel delivery to some degree The exceptions to the rule are the low speed adjuster and the regulator portion: the low speed
adjuster has no effect past 1/3 throttle. The regulator portion has no tuning effect past 1/4 throttle, although it continues to control the fuel supply.

IDLE STOP SCREW
The idle stop screw is used to adjust the idle speed (rpm) by opening or closing the throttle valve. Refer to your watercraft owners manual for the correct idle speed. As a rule of thumb, adjust the idle speed to approximately 1100 rpm.

Tachometer
you can adjust to run at idle 3-4 miles per hour, but you can attain precise performance with a Digital shop tachometer
http://www.watcon.com/Catalog_Pages/PET-2100_DX.htm For the serious mechanic or racer
Tiny tachs are a good alternative price-wise. For the average recreational DIY

LOW SPEED ADJUSTER
The low speed adjuster is used in conjunction with the idle stop screw to adjust and maintain idle speed and smoothness. Experiment turning the low speed adjuster in and out in small increments until a smooth idle is obtained. As the idle stop screw is turned in our out to raise or lower idle speed the low speed mixture is also affected. For clarification, if the idle stop screw is turned out to lower idle speed, this action increases manifold pressure slightly and richens the low speed mixture so that a mixture adjustment may be required. The low speed adjuster is very sensitive and adjustments should be made in small increments only.

Note: Remember, the low speed adjuster is only for adjusting the idle mixture. If you use the adjuster to help get rid of a low speed hesitation, you will probably find that your engine will load up in no wake zones, or after extended idling.

POP-OFF PRESSURE AND LOW SPEED JET
How do pop-off pressure and the low speed jet work together?
These two circuits overlap, although the low speed jet continues past 1/4 throttle where pop-off pressure has little to no effect. In general, if your pop-off is slightly too high, you can compensate by increasing the size of the low speed jet. The opposite is also true; if the low speed jet is slightly too small, you can compensate with less pop-off pressure. Once you get to the point where you think each is adjusted correctly, it's best to try varying the two to make certain you have the best combination. For example: If you have pop-off pressure of 30 psi and a 67.5 low speed jet, you should also try a pop-off of say 35 psi and a 70 low speed jet. To verify that you have the correct combination there are two things to test:

1. Throttle response should be crisp, with no hesitation.

2. Ride the boat at a constant 1/4 throttle opening for about 1 minute and then quickly open the throttle fully, there should be no hesitation and the engine should not show signs of being loaded up. If it hesitates, it's lean; if it's loaded up, it's rich. The first test is to check pop-off pressure, the second test is checking the correctness of the low speed jet size. Take the time to ride the boat slowly and thoroughly test your jetting changes. After a jet change, it takes the engine a few minutes of use to completely respond to the change.

When does it become necessary to adjust pop-off?
When personal watercraft come from the factory they have fairly high pop-off due to the fact that they also have somewhat restrictive air intake systems that cause the engine to generate very high manifold pressures; the higher the manifold pressures, the higher the pop-off pressure required to properly regulate the fuel delivery to the engine. As you modify or change your watercraft's flame arrestor to a less restrictive type you will most likely start to experience a lean hesitation caused by a decrease in manifold pressure. This change will require an adjustment in pop-off pressure to regain crisp throttle response. Because most
aftermarket flame arrestors are less restrictive than stock, you will need to decrease pop-off to compensate.

Only use Genuine MIKUNI carb kits and Mikuni needles & seats.
look for the Mikuni ID marking that looks like a square right before the needle size, and on bottom of seat.

The Super BN carbs that come from Mikuni America are already set up for performance applications, and come with pop-off settings lower than the carbs that come as original equipment. Pop-off pressure, (the regulator portion of the Super BN) is a tuneable component of the Super BN and works in conjunction with the low speed jet for good initial throttle response. The components that make up the regulator portion of the Super BN are:

1. Needle Valve, available in 4 sizes, 1.5, 2.0, 2.3 and 2.5 (Note: Some OEM carbs have 1.2)
2. Arm Spring, available in 4 sizes, 115gr., 95gr., 80gr. And 65 gr.
3. Arm
4. Regulator Diaphragm

Spring Chart
115 gram = gold spring
95 gram = dull silver spring
80 gram = black spring
65 gram = shiny silver spring

115 - Mikuni Reference Number 730-03030
95 - Mikuni Reference Number 730-03033
80 - Mikuni Reference Number 730-03027-T
65 - Mikuni Reference Number 730-03027



The arm has a limited range of adjustment; from the arm being level with the adjacent carb surface to being bent upwards no more than .040" (1mm) above that surface. If the arm is bent upwards too much, it can cause the needle valve to be held open when the diaphragm and cover are installed. If the arm is bent down, its movement becomes limited and may not be enough to allow the needle valve to open fully.

ADJUSTING POP-OFF PRESSURE
Pop-off pressure is adjusted by replacing the arm spring with one of a different gram rating. Sometimes, in order to achieve the desired pop-off pressure, it is also necessary to change the needle valve size; keep in mind that it's always best to use the smallest needle valve size to obtain the correct pop-off pressure. ALWAYS recheck pressure AFTER reassembly of your carbs.

MEASURING POP-OFF PRESSURE
You can measure pop-off pressure with a "pop-off" pump, available from Mikuni through your dealer.
http://www.watercraftsuperstore.net/PWC-Tools-Shop-Supplies/709SB021.html About $50 or You can make one.

CHECKING POP-OFF WITH A POP-OFF PUMP
1. Attach the pump to the fuel inlet nipple.
2. Cover, or in some way plug the fuel return nipple.
3. Remove the regulator diaphragm to observe the needle valve.
4. During testing, it is important to obtain consistent readings. To accomplish
this, it is necessary to keep the needle valve wet. Use WD-40 or something
similar to wet the needle valve. Note: Don't use gasoline because of the fire
hazard. Protect your eyes from the spray when the needle pops open.
5. Pressurize the carb with the pump until the needle valve pops open, being
careful to note the indicated pressure. Test the valve 3 times to assure an
accurate reading.

An indication that your pop-off needs to be adjusted is a lean hesitation when you open the throttle from idle; in the extreme, the engine may even die. It is much easier to detect a lean pop-off than it is a rich one, so it is wise to adjust your pop-off until you get it too lean and then back up until the lean hesitation disappears.

Note: It is recommended that you do not use too large a needle valve for your
application. Many tuners recommend using 2.3 or 2.5 needle valve in all cases. Actually, we recommend using the smallest needle valve that gives you the correct pop-off pressure for your engine. A 1.5 needle valve can flow the maximum amount of fuel that the Super BN can pump, so the only reason to use a larger needle valve is to obtain the correct needle valve and arm spring combination (pop-off) for your watercraft.

HIGH SPEED JET/THROTTLE POSITION AND JETTING
The high speed jet begins contributing fuel at about 3/8 throttle, overlapping the low speed jet. The high speed jet is the primary tuning component from ½ to 3/4 throttle. As you have probably noticed, tuning circuit operations are denoted in fractions of throttle openings.. the reason for this is simple: Carb jetting does not relate to engine rpm or the boat's speed, it only recognizes how far the throttle has been opened; each circuit of the carb responds in turn. This is why it's very
important, when trying to diagnose a carb problem, that you identify at which throttle opening the problem occurs, in order to adjust the appropriate circuit.
The procedure for testing for the correct high speed jet size is the same as for the low speed, except that you should now hold the throttle at a constant ½ open for one minute, then quickly open the throttle fully to check engine response. If the engine hesitates, the carb is lean. If the engine takes a second or two to clear out and then accelerate, the carb is too rich. In either case, make the appropriate jet change and do the complete test again.

HIGH SPEED ADJUSTER
The high speed adjuster is the last circuit to adjust. It primarily controls fuel delivery from 3/4 throttle to wide open throttle. Turning the screw clockwise reduces fuel flow, counter clockwise increases fuel flow. The maximum fuel flow is achieved at three turns out from closed. To test the high speed adjuster it is recommended that you start with a fresh set of spark plugs to get quicker plug readings. Unless you have an exhaust gas temperature gauge, you will have to rely on plug readings. You will need to be in an area where you can hold the throttle wide open for several minutes (Factory Pipe suggests that you only do this for about 30 seconds, longer times with a lean setting could cause engine damage) then chop the throttle and stop the engine just prior to removing the
plugs to read them. Ideally, you're looking for a nice brown color on the electrode
Another indicator of proper adjustment is a maximum rpm reading on a tachometer. If the carb is lean or rich, it won't pull as high an rpm reading as when it's right on.

PERFORMANCE TIPS
The "Left Turn Syndrome"
You will find in all instances that your watercraft will turn more easily to the right than to the left. The reasons are basically simple. First, engine torque constantly places pressure on the hull to turn right. If your engine's performance is marginal, you can notice a dramatic fall-off in power in a hard turn. This power fall-off can't always be blamed on the engine, being over-propped can also cause the engine to slow enough to fall off its power peak. An engine with a peaky power curve is especially susceptible to a very dramatic power loss in a hard left turn. Most recently, with the increase of Sport and Runabout racing, there has been a marked improvement in hull design with a dramatic increase in "G" forces encountered while turning: over 2.5 G's. In some instances such a hard turn can cause momentary loss of power due to fuel starvation in the carbs. Jetting changes cannot correct this situation, the best solution is to rotate the mounting of the carbs 90 deg, so that their throttle shafts are perpendicular to the crankshaft axis rather that parallel. To date, this solution to the problem has been 100% successful.

Fuel Dripping From The Inner Venturi At Idle
This situation occurs periodically and is easy to cure. What causes this problem is a combination of two things. First, low pop-off pressure (due to installation of a 2.5 needle valve with a light spring pressure, for instance) together with an engine that has substantial vibration at idle. The engine vibration causes the needle valve to leak, which causes the engine to run even rougher. You can view this occurrence by carefully looking into the throat of the carb at idle, you will be able to see fuel dripping from the inner venturi. In this same way you can also check to see that the problem is corrected. The cure for the problem is to increase pop-off pressure until the dripping stops.

Engine Hesitation When Accelerating After a High Speed Deceleration
You may find it desirable to increase the number of anti-siphon valves (part# BN34/107), If you ride very fast and find that you have a noticeable stumble when reopening the throttle after a long, high speed deceleration. This is caused by excess fuel in the carb. The engine revs fairly high while decelerating, but it uses very little fuel. The fuel pump still pulses hard, but there is no demand for the fuel. A small amount of fuel will overfill the fuel chamber, leak through the high speed circuit and get deposited on top of the closed throttle valve. This fuel causes a momentary rich condition when the throttle is reopened. The solution is to use one or two additional anti-siphon valves. Never use more than two extra, and recheck your calibration after installing any extra valves; in some cases extra valves can adversely affect throttle response.
__________________

LEAN CONDITION Air leaks anywhere into the motor case will cause a lean condition. Backfireing may result.

Check to see if the throttle cable has slack in it when it is at rest. The most common problem of a runaway idle is that the last guy did not install the throttle cable with enough slack in it. But that only appluies to one that has had work done to the carbs or to the cables.
Sometimes richening the low speed adjusters will stop this runaway condition, unless the jets or filters inside the carbs are clogged up.

They run away because they are too lean for the amount of fuel being put into the motor. They get too mch air, and not enough fuel.

Air leaks anywhere into the motor will cause a lean condition.
Tight cables cause a lean condition.
Clogged fuel systems and pet**** valves and carbs cause a lean condition.
L.S. Adjusters set too lean cause a lean condition at idle speeds.

Engines that shut off by themselves when riding along are often seizing the pistons from a lean condition, same as if you pulled the lanyard off. When this happens, it is often mistaken for an electrical issue.

You cannot tune a motor without a load on it and the low speed adjusters are there for accelleration only. If you are lean, use the high speed adjusters.

WONT START WHEN HOT? A pressure test consists of two tests. One when assembling the carb, by installing the needle valve, the lever and the spring, then soaking the needle with gas or WD40, then pumping up the pressure and watching for bubbles around the needle valve, then more pressure to measure when it pops off.
The second test comes after full assembly. This is the one that gives you an idea if they leak or not. You pump up at least 10 psi and watch the guage to see if it leaks off. It should hod 10 psi for ten minutes.
What is happening if the needle valves are leaking after full assembly, is that the diaphrams that you installed over the lever, is actually holding the levers down enough to allow the otherwise good needle valves to leak. This can be stopped by bending those lever arms down a little bit so the nipples on the diaphram are not resting against the levers that open the needle valves..

Compression or Rotary Problem
If you install a rotary valve 180 degrees off, it will effect the compression readings in both clyinders but they should still pump a decent number and they should still both be even.

When the port is sealed off by the rotary valve when it should be open, you will get less air into the clyinders to compress. Atmospheric pressure is around 14 psi, an open port allows atmospheric pressure to aid in filling the clyinder with air to compress.

So, do not say it won't matter, because it will. But it usually is not the reason a piston shows low compression numbers.

Dual Carbs
Here's detail tricks on the carbs: Remove the cover, diaphram, and check valve block over the jets. Spray carb cleaner into the pilot jet, with the tube connected on the carb cleaner can. Look into the carb throat, and you'll see three microscopic holes and one larger one off to the right that has carb cleaner coming out when you spray. After spraying initially, get someone else to slip their finger over the large hole to increase pressure to the three small holes. You will actually see the streams getting larger as the cleaner cleans out the varnish in the holes. This step is critical, if you want to have crisp throttle response on the bottom end.
Synchronize your carbs! 90% of the time one butterfly opens more than the other, reducing performance, max rpms, throttle response, and fuel efficiency. Use a flashlight, and lay an inspection mirror in the carb throat. Open the throttle wide open, and visually line it up with the atomizer. Then check the other butterfly the same way. Zip-tying the throttle to the grip keeping it wide open makes it easier. Use 2-8mm open-end wrenches to break loose the locknuts on the coupler between the carbs and rotate accordingly to get the butterflies in the same position.
Insure the pop-off is the same or within 1 psi of each other, for fuel flow syncronation thru both the carbs. There are pointer arrows on the caburetors plates on the forward end of them. On your mag carb, the nipple at the center top of the first plate is for your pulse line. On the bottom, next plate back on the pump is your fuel inlet. Then, the last plate will have two nipples with arrows pointing in and out. The nipple on the plate with the arrow that is pointing in, actually is the cross connect for fuel going to the PTO carb. That line is connected to the plate which has the arrow pointing in. Then, the two nipples at the top of the carb left over connect to the "Y" for the return.

CHOKE ROD REMOVAL, DUAL CARBURETORS:
If you have the manual choke, the long stainless needle thru your dual carbs linkage nuts, remove the flame arrestor lower plate screws after you remove the mesh, to see the upper linkage, it takes a #2mm allen wrench on the starboard side into the center of the nut hole, is a set screw you must loosen a turn, to unsecure that long stainless needle from the two choke linkage plate nut(s).

Use an Impact Driver or cordless impact drill/driver #P2 bit to help loosen screws, or an Irwin Vise-grip LW-10 locking wrench

Seadoo.....uses the Metric measurement system, so buy/use metric tools.

For the carbs to work, you have got to have the flame arrestor on. This is what creates resistance, along with the manifold pressure created by the compression of the engine, to get the gas to the motor. So, if you don't have the flame arrestor on, you'll never get fuel to the motor.
Pay very special attention to the internal passageways for an accumulation of petroleum mineral and Aluminum Oxide deposit in the internal passages of the carb. Its like JB weld and has to be picked or drilled to remove this "coagulation" material from the passage walls.

QUICK CLEANING DUALS
Get a large can of carb cleaner. I used this to clean the internal filter screens...it can clean one in about 30 seconds.
Here's detail tricks on the carbs: Remove the cover, diaphram, and check valve block over the jets. Spray carb cleaner into the pilot jet, with the tube connected on the carb cleaner can. Look into the carb throat, and you'll see three microscopic holes and one larger one off to the right that has carb cleaner coming out when you spray. After spraying initially, get someone else to slip their finger over the large hole to increase pressure to the three small holes. You will actually see the streams getting larger as the cleaner cleans out the varnish in the holes. This step is critical, if you want to have crisp throttle response on the bottom end.
Spray carb cleaner into the main jet too, but don't look into the carb while doing it unless you want it in your eyes!
Make sure you spray carb cleaner through the hose barbs, in and out. Remove the needles to get good flow through the inlet barbs.
Synchronize your carbs! 90% of the time one butterfly opens more than the other, reducing performance, max rpms, throttle response, and fuel efficiency. Use a flashlight, and lay an inspection mirror in the carb throat. Open the throttle wide open, and visually line it up with the atomizer. Then check the other butterfly the same way. Zip-tying the throttle to the grip keeping it wide open makes it easier. Use 2-8mm open-end wrenches to break loose the locknuts on the coupler between the carbs and rotate accordingly to get the butterflies the same position.

GREASE CARBS
Use lots of grease on all carb threads, screws, adjusters, cable nuts & wire. Be
liberal on the complete exterior. My preference is White Lithium grease. They won't come loose and next time when you
need to clean the filters it will be easier.

When to change Gas Tank Breather Check Valves
A common cause is a carburetor needle(s) & seat(s) leaking fuel into the cylinders causeing a hard sto start condition when motor is hot. How can gas get past a needle valve other than what I have talked about? One way is if the fuel tank pressure release check valve in the OUT vent line thru rub rail is not functioning. The fuel pressure in the tank overcomes the spring tension on the needle valve and gas is FORCED past it. The valve should open at approx. 3-5lbs. psi.
The vent lines normally hold no fuel at all unless the tank has been overfilled. In that case, the line that leaves the gas tank baffel, the Y and line going overboard may have had gas inside of them, or may even have some gas laying in them now, at least the horizontial line might. I do not make a habit of changing those two lines, but I do suggest testing the check valves now and then, especially if you suspect a leaking needle and seat valve inside of the carbs and the one way out check valve in the vent line going overboard is not opening to vent off the pressure inside the gas tank. Plan on enough fuel line to replace
the short bafel to Y breath fitting, and cut it longways about 2" from where it was attached to the Y and see if it has any deterioration. If so, replace all vent line & the two check valves.

1996 XP 787 engine
1996 jetting specs are 142.5 HSJ's and 70 LSJ's, 80 gram black spring Mikuni Reference Number 730-03027-T and 1.5 Needles & Seat's.
LS adjusters at 1 turn plus or minus 1/4 turn out.
HS adjusters zero to 1/8th turn out.
Pop-off = 23 to 43, so, start at 33 PO, each carb set within 1 psi of each other.
http://partsfinder.onlinemicrofiche.com/seadooforums/Seadoo_oem/Seadoo_PWC.asp?Type=13&A=35&B=14

Carbs with accellerator pump
yes it will squirt when the engine's off.
look at the hoses coming from the accelerator pump. there will be two going to the bodies of the carbs- this will be the point at which fuel will squirt out. Works as an Excellent primer, for easy starting too!
So, This is an easy fix most of the time. Remove the air box. pull the accellerator pump hoses off of the fittings at the top of each carbureator. Using some pliers, grip the square portion of the accellerator pump nozzels and twist and pull until they come out of the carb body ( press fit ) soak them in some carb cleaner and poke into the hose side hole with a stiff wire, soak some more, then clean them out. The only real way to test them is to pump up a few psi of air pressure going into them with a pop off guage, hose adapted to 1/8th in id.
Or, put them back onto the carbs, pump the accellerator linkage a few times to verify fuel is coming out of the acc pump body and hoses, reattach the hose and with the carbs filled with gas, pump the throttle linkage a few times while watching to see if gasoline is squirting out of each of the two nozzels.
If there was no gas coming out before you started this proceedure, and now there is gas coming out, you solved the problem.

Motors that have the accellerator pump on the carbs cannot take off from a standstill without a big hesitation followed by normal accelleration, or the engine just dying out completely, causing you to need to restart it.

A black wet piston can indicate no ring sealing, low compression, ect because it cannot compress the fuel mixture enough to burn it all.

Its a common trend on the pre 1996 ski's to replace the fuel line (20' x 1/4"id) except from the two check valves to the two thru-hull connectors every five years, the two large 1/2"id and one medium 5/16"id oil lines from the oil tank every 8 years, and the oil filter 5/16" every two years, and the two 3/32"id x 6 1/2" long oil lines from the two oil injection pump barbs to the two cylinder rotary cover tube spigots every TWO years (or less). We recommend BRP mineral two stroke oil or the Rave Valve engine oil = BRP XPS Synthetic (a better blend) for longest crankseal & engine life.

SECURING your fuel - oil lines - drive boot ect
If you are useing stainless worm drive clamps put a couple wraps of electrical tape on the hose end then attach, your line won't get cut. I started useing 11" cable ties in liew of worm drive, and bought a tightening tool for el cheap ($8). Its like a pistol tool you put the tie tail in and squeeze trigger. Its the Best and Easiest secure fastening. Cable ties come in many sizes, from tiny to extreme.


THE LAKE TEST
then lake test it while tied to the trailer to see if it is running rich or lean on the initial throttle opening from idle. You do not want it to bog, then cleanout and accelerate suddenly. That would be too rich on the LS adjusters. Close them until the bog goes away. Leave your Airbox at home to easily access the adjuster screws at the lake. Insure the Flame Arrestor well seated.
If it wants to hesitate before accellerating, add more fuel by adjusting the LS adjusters out a bit more, never going much over 1/8th turn at a time until it just quits hesitating upon the initial hit of the throttle. Small increments between rides.
After making any LS adjustments, reset idle speed to 1500 rpm, and try accellerating the motor again to see if it hesitates.
Now you are ready to untie the hull from the trailer and go test the high speed jetting and HS adjustments out on the lake riding with seat off. You cannot test the HS adjustments and HS jetting, until after you initially set the idle speed and low speed adjusters on the trailer with impellor in the water.
You make a short full throttle run from a standstill. It should take off cleanly, with no hesitation or bog off idle and up through the rpm range to max rpm. ( you will notice a slight to pronounced jump in rpm when your rave valves open and your water regulator or ECWI changes the amount of water being sent into the exhaust pipe. The raves opening at around 5000 rpm plus or minus will be the more noticable jump in rpm and accelleration, followed shortly by the ECWI shutting the water off, if you can feel that at all. You should not drastically notice the ecwi shutting off when you get it set to go off at the perfect rpm. ) Take a very short full throttle run, and while holding the throttle pinned to the grip, pull the lanyard and coast to a stop on the water. ( if you can, leave the seat on the beach ). Reach into your pocket or the stroage tray and get your sparkplug wrench out and remove the sparkplugs. They should be a little more than warm in your hand and not so hot you want to throw them overboard. Be carefull not to drop anything into the hull or the water. Hint: After a few minutes of running time it is easier to read new sparkplugs, so do not use a brand new set of 'plugs if you can, but also, do not use old oil and gas fowlded plugs either. If all you have is new plugs, putt around the lake a few minutes, accellerating and deaccellerating, but do not push it to any limits and do not just putt along slowly either. Give the new 'plugs time to color up a bit before doing any real top end jetting testing at WOT.
When you have the high speed adjusters set right, the coloring of both sparkplugs should be somewhere in the light tan to dark brown range. Any color of tan or brown means it is not likely to overheat and sieze a piston. If you are just a lake racer, go for cardboard brown ( if you can achieve it ) after a full throttle run. You do not want colder to the touch sparkplugs with black or black and wet look to them. That is overly rich with the high speed adjusters or the size of the high speed jet itself. It may need a smaller high speed jet if the adjuster is fully closed and it looks to be too rich.
You also do not want the sparkplug to be too hot to handle with a bare hand on the porclean or the metal hex bottom of the plug after a short run at wot. That would look to be a pure white to grey coloring, possibly with specs in the coloring on the porclean below the electrode and grounding sparking tip would indicate it is too hot by the bluing of it. Hot metal turns bright red then blue as it cools off. It should have some light colored carbon build up from the end of the tip back to almost the part that bends 90* where it attaches to the metal sparkplug hex base. The longer distance that carbon buildup is on the tip, the richer the mixture will be until it is so rich that the tip looks black and wet.
Keep in mind, that anything less than about full throttle rpm will give you a false reading on the sparkplug. So, nevver rely on any sparkplug reading that is not directly after what we call a "plug chop" When you go hard and cut it off cleanly, with no deaccelleration while it is still running with the sparkplugs sparking. Always go hard and cut the ignition and coast to a stop before trying to do a high speed 'plug reading.
If after idling a long time, your 'plugs look wet and black the low speed adjusters may need to be closed a bit and if that does not solve it, install a smaller low speed jet.
Remember, a Mikuni High or low adjuster is effective from closed to two full turns out. Beyond two turns out, you need a larger jet for sure. We try to get the full out racing motors which need very high octane gasoline and racing carbs HS adjusters to be too lean at under 1/2 turn out and going onto the too rich side at about anything more than 1 to 1&1/4 turns out. Anything outside that range requires rejetting. We try to get the low speed adjusters to be perfect at about 1 to 1&1/4 turns out and not more than 1&1/2 to 1&3/4 turns out. As each race we attend and many times during the day of the race, adjustments are necessary due to atmospheric changes of air density and ambient air tempetures.


We suggest an annual cleaning of the fuel tank to remove any water that may be laying in the bottom of the tank as some gas tanks in all of the pwc's have alot of water in their gas tanks. This can cause big problems inside the carbureators if they sit all winter with any water at all inside of them.

Another thing is very important these days is using Marine Sta-Bil. It keeps the gas tanks and fuel systems clean, while also protecting the carb(s) internal parts from rotting or rusting now that ethonol is part of their daily diet when you are using them. Besides water, ethonol creates alot of corrosion when on aluminum and that is that white dusty looking substance that we find inside dried out carbs and fuel selector valves. Marine Sta-Bil is BLUE, Automotive is RED. If you ride Saltwater, Please use BLUE MARINE STA-BIL.

In case you are unaware, ethonol, even if only 15%, will attact the water molecules from the air inside the gas tank. Over time this will develop into a big puddle of water inside the gas tank, laying on the bottom of the tank waiting to be all skaken up and mixed up with the fuel going into the Fuel Bafel Circulatory then carbs. Ethonol may be the one biggest reason that the carbureated pwc's have so many carb issues, clogged up filters, selector valve clogs and rotten delaminating fuel lines. Do yourself a favor and treat each tank of gas with a gas conditioner that removes moisture from the tank and carbs, and condition the fuel & delivery system from ethonol abuse.


To Remove the Fuel Selector valve switch.................Clean......or replace.
Use a pointed blade to pry the plug in the center of the plastic selector switch, and remove the #2 phillips screw. Use a plier to grip the selector handle in the center to pull and gently rock the cap til it comes off.
Remove the nut with a 1 3/16" socket, and the washer(s). Tap the valve lightly until it falls into the inside of the hull. Reach in thru the front hatch to pull the valve toward you and write or mark each fuel line, ON,
RES, and OUT (going to the fuel water separator/filter). After removeing the lines take the valve to your workbench if it has a small screw in the side of the valve, otherwise buy a new valve. Next you will need a
veriable speed small electric drill and a 9/64" bit and a 11/64" drill bit. Remove the small #2 phillips screw and set aside, note the end is tubeular. Use a plier to pull the center selector plug out of the valve houseing.
It has a small 0-ring to prevent fuel loss and you will grease that rubber ring with a light coat of vaselin when you re-install. Note the trough on the plug where the #2 screw rides in. You will need to align that when
you re-assemble. Put the 9/64" bit in your drill and slowly drill the hole in the side of the plug, then change to the 11/64" and drill the hole in the end of the plug til both holes are 90* (degrees) and air-chuck all
drill particles. Next use the 11/64" bit into the "OUT" tube of the houseing and look down in the adjacent hole to see the when the bit reaches 90*, and stop the drill and mark the depth on your Bit at the end of the OUT
tube. Use that mark as you next drill the two ON & RES tubes to that depth and again air-chuck clean any crud particles. Your valve houseing is ready for re-assembly and installation, More free flowing than new! Only hand
snug the hull nut as it is only plastic and take note of the alignment hull hole and the valve's orientation bump as you re-fit thru-hull. Liberally marine grease the exterior of your valve body as you would your carb(s) prior to re-installation.

Seadoo Motor Break-in
These are Industry Standard New Engine/Top End instructions, and apply to all models with the exception of the DI and 4-stroke equipped models.

You canot break-in an engine out of water. Your fuel delivery system must be completely clean and free flowing.

Proper break-in of your engine is the most critical aspect for determining the longevity and performance of your engine. Engines not properly broken-in will often fail within the first minutes of operation. Ring failure and piston seizure are the most common symptoms of an improper break-in procedure.

If you have a pre-mix system (mixing oil and fuel in the fuel tank), then you should richen the ratio to about 32:1 for the first ten gallons of gas. If you have an injection system (putting oil in a separate oil tank), then you should put 50:1 premix in the fuel tank along with the oil injection system for the first ten gallons of gas.

During the first 10 gallons of gasoline, there should be NO full throttle operation. First idle the engine for about 10 minutes to ensure that the engine is properly warmed-up. Then begin varying the throttle position up and down, up to 20% throttle for a half hour. Then come back and let the engine cool off completely - it should be a good 30 min break. After it cools down, you may now ride it up to 50% throttle for another half hour or so. Then come back again and let it completely cool down again. Now you can go out and ride up to 90% throttle. Continue this for the remainder of the 10 gallons, never holding one throttle position for more than a few seconds. Do not run at a steady throttle position and do not go to 100% throttle. After your first tank of gas, replace your plugs with fresh ones. For the second tank, you may ride normally with one exception - do not hold it at 100% throttle for more than a few seconds. After the second tank of gas, you are completely broken in and may ride anyway you like.

Bills86e

INSIDE A FUEL MODULE :
http://www.youtube.com/watch?v=QbzEeWy1b3o&feature=relmfu

IN-TANK electric module replacement fuel pump: Sales@highflowfuel.com about $80 with filter & wire kits
Direct Injection (109 psi) : pump item # 342
RFI (59 psi) : pump item # 382
sales@highflowfuel.com = Tell them the pump # you want.

HOW TO INSTALL 342DI pump = Credit to DOOWACKA
http://www.seadooforum.com/showthre...el-Pump-Replacement-Guide&p=325621#post325621

Site: http://highflowfuel.com/search.html?q=342&go=Search
select a vehicle that uses the pump # you need, as they are all the same pump kit. They don't list watercraft (pwc's). (update) NOW THEY DO: #HFP342DI

Fuel Injector Cleaning
http://www.youtube.com/watch?v=-07scn8nXq4
http://fuelinjectorman.com/

READ ALL POSTS< ....VIDEOS........> MORE INFO BELOW
 
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LouDoo

Moderator
Moderator
Messages
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192
Location
Lexington, KY
Water Crafts
SeaDoo's: 96 GTI 720, 95 XP 800 Limited, 96 GSX 787. 2000, 18' Bayliner 3.0L.
#2
Bill,

Thanks, I've copied this and put it in my "PWC" file. Lots of great information.

Lou
 

Bills86e

Premium Member
Premium Member
Messages
3,349
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82
Location
TampaBay, Florida
Water Crafts
Sea Doo 95, XP, SPX, GTX,
SPI, XP, 97 Polaris Hurricane
#4
RECAP: (even if you are just cleaning the internal filter)
Remove the cover, diaphram, and check valve block over the jets. Spray carb cleaner into the pilot jet, with the tube connected on the carb cleaner can. Look into the carb throat, and you'll see three microscopic holes and one larger one off to the right that has carb cleaner coming out when you spray. After spraying initially, get someone else to slip their finger over the large hole to increase pressure to the three small holes. You will actually see the streams getting larger as the cleaner cleans out the varnish in the holes. This step is VERY critical, if you want to have crisp throttle response on the bottom end.:cheers:
 
Messages
21
Likes
0
Location
st pete FL
Water Crafts
1994 SeaDoo GTX
#5
This guy really knows his stuff! I've seen it first hand....incredible info for someone(like me), really wanting to learn the engineering/physics of how the machines work.
 
Messages
21
Likes
0
Location
st pete FL
Water Crafts
1994 SeaDoo GTX
#6
Actually, saved me from turning my 94GTX, 2 weeks owned/bought, from tuning it into anchor, or new, small "artificial" reef somehere in Tampa Bay, the water, I mean...:thumbsup:
 
Messages
846
Likes
9
Location
midland Texas
Water Crafts
2 - 1996 seadoo xp's
#9
Thanks for the post bill, It has been almost 3 years since my carbs were rebiult, and at the end of this year i am planning on doing it myself and learning, Would it be a bad idea to just replace everything like getting the kit and even the needles and seats, so basically its new again.
 

Bills86e

Premium Member
Premium Member
Messages
3,349
Likes
82
Location
TampaBay, Florida
Water Crafts
Sea Doo 95, XP, SPX, GTX,
SPI, XP, 97 Polaris Hurricane
#10
Pictures can be found in the Shop Manual, Mikuni.com, Seadoosource.com, Snipes Corner in this forum, How-To section of this forum. http://www.seadooforum.com/showthre...el-Delivery-Problems-low-revs-bogging-surging
Others, and in Similiar Threads in bottom left of this page.

http://www.mikuni.com/pdf/sbn_manual.pdf

SBN----PICTORAL----Credit = Short Block Technologies
http://www.shopsbt.com/forum/t12015/

Yes, Always buy genuine Mikuni carb kit(s) and needle/seats. Each ski's carb specs differ, read up on yours in the Shop Manual.!
Your SBN's rubber componets can get hard, fail to seal:
http://www.youtube.com/watch?v=cDsfsw0_M_o
http://www.youtube.com/watch?v=CnAkTH-wWkI

Use WD-40 on your needles & seats when adjusting the Pop-off pressure:
http://www.youtube.com/watch?v=ieMgEoppHq0

After re-assembly & leak-down (5psi for 5 min) test, paint the carbs and grease them up, and your cables. Grease is your friend!

RAVE VALVE---PICTORAL----Credit to RAMPAGE
http://www.seadooforum.com/showthread.php?37588-How-to-service-Rave-Valve-Pictorial

Seadoo/Mikuni carburetor mixture & pop-off specs. Credit to: Seadoosource
http://www.seadoosource.com/carbreference.html


Mikuni Spring Color & Popoff Pop Off Chart

115 gram = gold spring
95 gram = dull silver spring
80 gram = black spring
65 gram = shiny silver spring

115 - Mikuni Reference Number 730-03030
95 - Mikuni Reference Number 730-03033
80 - Mikuni Reference Number 730-03027-T
65 - Mikuni Reference Number 730-03027

It never hurts to look inside of a set of carbs every few years, especially if you have any poor idling, surging, accelleration, or flooding issues. In fact, even without those issues, it is good to stop them before they start, and save alot of money in repairs.
 
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grgfraz

New Member
Messages
8
Likes
0
Location
fairfield ca
Water Crafts
xpx seedoo 1995
#11
got my ski running nice now thanks bill the 3 little transfer holes were dribbling carb cleaner like you said so i blew them out several times and now they spray freely fixed my problems
 

Bills86e

Premium Member
Premium Member
Messages
3,349
Likes
82
Location
TampaBay, Florida
Water Crafts
Sea Doo 95, XP, SPX, GTX,
SPI, XP, 97 Polaris Hurricane
#12
Next the Lake test and the Final adjustsments for a crisp throttle responding ski! *plugs should be turning Mocha Brown after 10-15 minutes.

Credit to SeadooSnipe..............What *plug reading can tell you in tuning your ski.
http://www.seadooforum.com/showthread.php?4151-Snipes-Korner...


Key to Success
You can avoid rebuilding for years and years if you get into the habit of fogging your motor after using it.
Grease is your friend, use it on all aluminum componets like carbs, stainless cables, zerk(s) every 5 times out.
litheum on latches and rubber parts, petroleum jelly on plastic like gauge face and vinyl seats ect.
 
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deepdiver

Active Member
Messages
224
Likes
3
Location
Cullowhee, NC
Water Crafts
(2) SeaDoo 1995 SPX 5874
#13
Just realized only one of my bypass jets was squirting. Gotta go back and figure out how to get the other two open.
Thaks for the ref to Mikuni manual. Great reading to understand our carbs.
 
Messages
2,009
Likes
16
Location
Central Florida - Lakeland
Water Crafts
1996 Seadoo GTI
2001 Seadoo Challenger 2000
1996 Seadoo XP - project
2005 Aquatrax F12X
2003 Aqu
#14
Bill, do you do carb rebuilds? I have a 1999 GTX LTD that will not idle. Once above idle it runs well. Over the winter I had it in the garage with fuel stabilizer and would typically run it once a month. I did go from February to March without starting it and then the difficulties began. I am just east of Tampa and get over that direction regularly.
 

Bills86e

Premium Member
Premium Member
Messages
3,349
Likes
82
Location
TampaBay, Florida
Water Crafts
Sea Doo 95, XP, SPX, GTX,
SPI, XP, 97 Polaris Hurricane
#15
Yes, We do at: Leading Edge Watercraft Services
Give us a call at 727-547-9300, Bring your ski, Inside storage:
6675 102nd Ave. No. Unit "C"
Pinellas Park, Florida
 

BMANN06

New Member
Messages
1,537
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16
Location
Belleville, ON CANADA
Water Crafts
04' RXP
#17
Quick Question / Or Confirmation

Bill,

I rebuilt my carbs over the winter and I see a huge improvement. I don't think I'm quite out of the woods yet (need some fine tuning).

My Question is:

Can I make the adjustments to the LS screw with the Airbox off and just have the flame arrestor on? Reason I ask its a real PITA to pull the two airboxes off make a tiny change to LS screw put everything back together to find out I need to make more small changes.

Many thanks again GREAT POST!
 

Bills86e

Premium Member
Premium Member
Messages
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Location
TampaBay, Florida
Water Crafts
Sea Doo 95, XP, SPX, GTX,
SPI, XP, 97 Polaris Hurricane
#18
Yes you can. Thats how to acheive reaching the adjuster screws easily. Flame arrestors in place in the mounting plate and gas tank full.
Small 1/16th turns at a time.
 

norman88

New Member
Messages
14
Likes
0
Location
Canada
Water Crafts
2001 GTS 718cc
#19
WOW This is awsome.

Wow what an awsome description of carburetor adjustments. I have already printed it to .pdf and saved it. One question though...which will eventually follow:

I have a 2001 GTS which has a 718 cc engine. I just bought it today, haven't had it in the water yet since the battery was dead when I bought it and it's still charging, we jumped it to make sure it ran before I bought, (off topic...I paid $3200). Anyway, I downloaded the service manual, I've checked the compression (135psi on each cyl). The oil was about 3/4 full in the "jet pump resevoir" (cone at the back end), I topped it up. I took off the airbox, all with the carbs look ok. The guy said it was running fine 2 years ago when he last had it out. It got oil, gas, ready to go probably tomorrow. I know very little about sea-doo's, this is my second watercraft, my last was a polaris 10 years ago (which I really regret buying). I've tuned/balanced one 2-stroke multi-carb engine in the past - as in my BRP Formula III tripple 600 Ski-doo some years back. I've heard of and seen one multiple cylinder (2 or 3 cyl) machine with multiple carb buring holes in the pistons because of lean conditions in one or more cylinders.

So the question is, with this single carb sea-doo, is it more difficult to burn up a cylinder because of a lean condition? I postulate that in order to burn up one cylinder that cylinder would have to be leaking in air somewhere or somehow being robbed of fuel? With just one carb I would think it would be almost impossible to burn up a cylinder? I just want to know because I'm taking it out on the water tomorrow and don't want to burn up anything....

thanks!!
Richard
 

ocod

Well-Known Member
Messages
3,756
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42
Location
Miami
Water Crafts
2014 FX SHO // 2015 VXR
#20
Hi bill I'm hoping you can claify something
The 717 carb in my boat has no pump assembly on the fuel filter side. Its just one cover, a black gasket(film/seal) then access to fuel filter.

I have a got a 95 xp that I water tested toady. It worked fine for 15-20 mins then quit. I see spark when I ground plug but plug hole only shoots air out when I crank it and plugs are dry. I know carb is getting fuel b/c my hand is soaked with fuel when I cover opening to choke it (ski has no spark arrestor. Has slip on k&n).
The carb is not original to 717 but is a mikuni??
This carb HAS the pump assembly. It has two covers before getting to fuel filter. #53 on micro fish

http://partsfinder.onlinemicrofiche.com/seadooforums/Seadoo_oem/Seadoo_PWC.asp?Type=13&A=27&B=9

The difference is the use of that 2nd plate on the fuel filter side. Why is it there??

My question is can I delete that 2nd plate.

I also have a set of the dual carb from a 717 that one carb has pump and other carb does not. I'm thinking of taking carb w/o accelerator pump to test ski if other Mikuni is causing ski to not run right b/c its not original to 717 i think?? Intake even looks different from whats in my boat...


Sorry if not on topic.


edit: Think I got it after 20+ pages of searching. Pump assembly works as internal fuel pump. Where as my boat has fuel pump seperate. So there is no removing unless external pump added. I thought the engine would provide vacuum to draw fuel.
 
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Seadoobuddy

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Premium Member
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7,139
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72
Location
White Lake Township, Michigan, also some in Braden
Water Crafts
96 GTX , 99 GSX Limited, 19 ft. Glastron I/O boat.
#21
Bill,
Many thanks for posting these tips. I'm live in Michigan but have a house in Bradenton.
Question...I know what hesitation is but by "load up" do you mean bogging down by running rich? if not then what's the difference?
Thanks from a newbie.
 

Bills86e

Premium Member
Premium Member
Messages
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Location
TampaBay, Florida
Water Crafts
Sea Doo 95, XP, SPX, GTX,
SPI, XP, 97 Polaris Hurricane
#22
Definitions: This is written for your boat being in the water. You need the load of the water for accurate tuning. Stay close to shore and don’t get too far out.

Rich: Too much gas
rich hesitation is when the ski seems to go lower in RPM's and slowly comes back to life. BBrrrrrrrrrrraaaaaaaapppp!

Lean: Not enough gas, too much air.
Lean hesitation is sounds like the ski dies for a split second and comes back to life. BB__rraapppp!

Bog equals a rich condition; symptoms of a bog are that the motor will not rev up right away because it needs to burn off excess fuel that is being put into the motor because the low speed adjusters are too far opened. If you were to let it idle for a minute or two, the sparkplugs would look a bit wet with fuel if you were to remove them without revving up the motor first. If the engine takes a second or two to clear out and then accelerate, the carb is too rich.

Hesitation. A lean hesitation happens when you stab the throttle from idle, and it acts like it is taking a huge deep breath before revving up, or it just completely dies for lack of fuel. The latter would be a very lean condition probably caused by the accelerator pump not working correctly, or the low speed adjusters are turned way too far in. If the engine hesitates, the carb is lean.

loading up: An excessive gas flow into the cylinders.

If they are very dry, you are not getting enough fuel. Something is assembled wrong or something is clogged up, like the brass jets, internal fuel filters or the fuel selector valve.


Before you start.
Start rich!! start 2 turns out on both and see how the boat reacts. You are going to have to play with it because regardless what the book says you have a lot of different factors. Elevation, compression, etc. Every boat will tune different and a similar boat will have different ideal settings.

Before attempting to tune, always clip the sparkplug wires to make sure you have a good connection at the sparkplug boots on the wires. You also should know that the motor has good compression because you cannot tune a junk motor.

You cannot properly tune an engine that has low compression in one or both cylinders.

Carburetors are a compromise at best, and tuning them for anything EXCEPT idling and full throttle use is always a compromise.

Can I ruin my motor doing this? YES!

A rich motor will run terrible, but will not kill your motor.
A lean motor will kill your motor.

How can you tell if it’s too lean?
Most novice tuners cannot properly read sparkplugs. We show examples, but do not rely on them.

A good indication of a lean motor is if the sparkplugs get so hot you cannot lay them on your opened hand without burning yourself. So when you pull your sparkplugs, do they feel real hot, or do they feel normally hot? Really hot is an indication of a slightly too lean motor and it takes no plug reading skills or special tools or instruments. Fuel works an engine coolant.

GUYS........Please ask further questions in the forum, Trying to keep this thread short and yet informative.

........BILLS86E........
 
Messages
80
Likes
0
Location
Austin, Texas
Water Crafts
1994 GTX, 1994 XP
#23
Bill, this is GREAT! I'll keep it short here, you are giving me some pointers in the premium discussion session.. This original post is awesome and I thought I understood it all until I read on to your follow-up details. First time I have worked on PWC, and this makes it great. CANNOT get this type quality info e en in the best shop manuals! Popsslowdog
 

BamBamHD

New Member
Messages
1
Likes
1
Location
Salem WI
Water Crafts
2002 Seadoo LRV
1997 Yahmaha GP1200
1994 Polaris SL750
#24
SeaDoo LRV DI Fuel Module Fuel Pump Replacement

View attachment SeaDoo LRV DI Fuel Module.pdf

Bill
Thanks :thumbsup: for the heads up on the replacement fuel pump for the Fuel Module it save me over $800 in parts quoted by the dealer which didnt include the labor and extras.
Attached is how I incorporated this new fuel pump innto the existing fuel module.
Thanks BAM
:coolgleam:
 

Bills86e

Premium Member
Premium Member
Messages
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Location
TampaBay, Florida
Water Crafts
Sea Doo 95, XP, SPX, GTX,
SPI, XP, 97 Polaris Hurricane
#25
Sticky's & How-to articles

These are intended to be read as information only, like "Library Books" do not write in them. PLEASE ..Use the Forum for asking questions, talking, getting help, ect. Thanks, Bill

Please think three or four times.....Before inking these! A Question...go to a forum. reply if you can add... TRUE... helpful information.

Bills86e and SeadooForum
 

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