717 NO fuel from PTO carb and other issue...

[powerslave]

Did a top end on my 95 xp. Two strange things. PTO carb will not deliver fuel. Mag carb will. Also, when trying to get pto carb to deliver, engine locks up. Pull plugs, turns over fine, then may lock up again.??? Also did mild rebuild on both carbs. Basically everything expect for needle

 

[1983]

MAG ( front carb closest to steering ) is only carb that has fuel pump. It has outlet nipple that feeds fuel to second carb ( PTO carb near driveshaft ) then the outlet from PTO carb goes back to tank.

MAybe you are saying carbs will not provide fuel while running or trying to start?

The needles and seats are jsut as important as the rest of the carb when doing rebuilds. THey ultimately wear out due to crap in fuel ( ethanol ) and vibration wearing out the needles tips. Which allows fuel past and times when you dont want it leaking past and causing flooding.

What is the pop off psi on each carb? did they pass leak down test?

Rob

 

[powerslave]

Didnt do pop off. Don't have a gauge. Didnt know mag carb only had the pump. That carb is delivering. pto, i dont know why its not. It won't deliver when trying to start.

 

[1983]

Outlet from mag carb feeding inlet on PTO carb may be plugged.

Pop off and pressure test are very important in operation of these carbs.


Rob

 

[powerslave]

I understand that. Any pop off tester work or is there a specific one that seadoo owners like? Thanks for your time.

 

[Austrian Rotax]

Any aftermarket pop-off tester will work I haven't heard any complaints about SBT pop-off testers or there are genuine mikuni pop-off testers but i imagine they are more expensive just make sure you get one with a range between 0-60psi at least. You can build your own pop-off tester, there's a thread in the how-to section about building one. You probly already know this, but you didnt change the pop-off spring right? and make sure the needle control arm is level with carb body. and if you need new needle and seat assemblies OEM mikuni are best. I dont know if SBT n/s are good or not they have the viton needle tip anyone heard if sbt n/s are good? sry to hijack.

 

[racerxxx]

Here you go, a pop off with max pressure hold. That way there is no second guessing what it popped at.

http://osdparts.com/index.php?main_page=product_free_shipping_info&cPath=595_602_1&products_id=8069

Sent from my SGH-T889 using Tapatalk

 

[Sportster-2001-951C-Stock]

Assuming the fuel is reaching the 2nd carb, the metering needle must no be lifting off the seat (for whatever reason), could be wht metering arm spring is too strong or the metering arm is bent out of position and the metering diaphragm isn't actuating the metering arm..

Did you reuse the original metering springs (recommended if not adulterated previously)?

To get the pop dead-nuts, you need a source of air pressure with a pressure gauge.

 

[powerslave]

I lightly push down the needle with my finger and it raised effortlessly. I want to learn how to do it myself but would be interested in what knowledgeable people charge here for a dual carb rebuild.

 

[Sportster-2001-951C-Stock]

Yeah, I think [MENTION=41828]Minnetonka4me[/MENTION] can do the carbs for you.

Hey on the lock-up thing does it seem like the starter is maybe a little too weak to get it past the compression stroke or does it seem more like there's a mechanical issue? The reason I ask is I can imagine if the cylinder ports weren't chamfered around the edges after boring then the piston ring edges might be snagging in the port.

 

[powerslave]

You're right, I think it might be the starter is weak. Rebuilt it last year, oem. I don't think the rings are snagging. At least I have a couple months before I really need it. Plus, I feel good doing some of this myself. (as long as i do it right

 

[RodInEscondido]

Here you go, a pop off with max pressure hold. That way there is no second guessing what it popped at.

http://osdparts.com/index.php?main_page=product_free_shipping_info&cPath=595_602_1&products_id=8069

Sent from my SGH-T889 using Tapatalk

If you have a max pressure hold feature, this will keep you from seeing where it drops off to ... or is this just applicable to the old beasts I work with which give both a pop-off and drop-to value which I guess would be sort of a measure of how efficiently the spring and seat were working. Just thinking again.

powerslave, there are several examples of home-built pop-off testers on this forum. If using air compressor as source, gotta be careful of overpressure; I generally find that by using clear vinyl line it will pop off the fitting at about 50# which is my safety valve when using this method. I do, however, use the hand pump tester in most cases ... no real setup needed.

In any case, after about the 4th or 5th iteration of having the wd40 covering the needle/seat spitting in your face you will learn to cover it during the test.

 

[powerslave]

I bought a mikuni pop off tester. Thought about making one but just went ahead and hit the buy now button lol

If you have a max pressure hold feature, this will keep you from seeing where it drops off to ... or is this just applicable to the old beasts I work with which give both a pop-off and drop-to value which I guess would be sort of a measure of how efficiently the spring and seat were working. Just thinking again.

powerslave, there are several examples of home-built pop-off testers on this forum. If using air compressor as source, gotta be careful of overpressure; I generally find that by using clear vinyl line it will pop off the fitting at about 50# which is my safety valve when using this method. I do, however, use the hand pump tester in most cases ... no real setup needed.

 

[powerslave]

I read somewhere here that if the flame arrestor is not on the carbs, the engine will not get fuel. Could that be the problem with my pto carb not getting fuel? Of course the flame arrestor is not on while im working on it. Should I see the pto carb getting fuel while looking down the carbs?

 

[Sportster-2001-951C-Stock]

If the flame arrestor is missing, you're likely to have to use more choke to get it started, it should still fuel while idling. The WOT and prehaps even mid range will run but likely too lean though, so there's some danger of overheating the piston without the air box (flame arestor).

What was the pop pressure you measured on the PTO carb, same as MAG carb?

Is the carb getting fuel, or is it not fueling the cylinder (there's a difference, if it's not getting fuel it cannot meter fuel to the cylinder)?

How did you determine the PTO carb isn't metering fuel? (I feel for warmth of the spark plug)?

I doubt you can see the fuel by looking down inside the carb at idle speed, the fuel comes from the idle port on the engine side of the butterfly at idle. The large venturi begins to flow only if the throttle is opened maybe 25% or more (hard to test this on a trailer without over revving).

I wonder if perhaps the linkage between the carbs is misadjusted (not synchronized), so maybe the PTO carb butterfly is not in the correct position (closed more than the MAG carb butterfly).

Attached drawing shows all three of the possible fuel flow paths (idle port, Bypass Ports (AKA: Transition ports), Main Venturi) The main venturi doesn't flow until there's a load on the engine while in the water b/c the throttle needs to be open some amount to increase the velocity of air across that big venturi.

How about the main venturi mylar check valve (circled in blue) held by a single screw on the kidney shaped metering plate, it's not bent is it? If the mylar piece doesn't seal flat over the hole and against the metering plate you might experience no fuel at idle speed b/c air will come backwards from the Main Venturi into the metering chamber thus the metering valve might not pop and allow fuel into the chamber at idle.

Also keep in mind, fuel is provided on demand based on vacuum, the metering diaphragm doesn't move inward into the metering arm and pop the inlet valve open unless there's a vacuum signal. If the mylar check valve is damaged then there might not be enough vacuum to operate the metering diaphragm at low speed (such as idle).

 

[powerslave]

I didn't look at the venturi mylar check valve circled in blue. I will. As far as pto carb not getting fuel. With flame arrestor off, i can see fuel in the mag carb but none in the pto carb. I did a rebuild and pop off was both at 40 psi. My problem now is, I replaced the 2 round check valves and when I did the mouth pressure/vacuum test, I can get both on the inlet out outlet tubes. So, I guess my check valves aren't seating well. I didn't have the blue lines and could not see any curvature on the valves when I put them on a mirror, so I just installed them using the dental floss method which worked great.

It seems to be not getting fuel to the cylinder. The pto and mag carb both had fuel in it.

And the butterflies are synced as well.

If the flame arrestor is missing, you're likely to have to use more choke to get it started, it should still fuel while idling. The WOT and prehaps even mid range will run but likely too lean though, so there's some danger of overheating the piston without the air box (flame arestor).

What was the pop pressure you measured on the PTO carb, same as MAG carb?

Is the carb getting fuel, or is it not fueling the cylinder (there's a difference, if it's not getting fuel it cannot meter fuel to the cylinder)?

How did you determine the PTO carb isn't metering fuel? (I feel for warmth of the spark plug)?

I doubt you can see the fuel by looking down inside the carb at idle speed, the fuel comes from the idle port on the engine side of the butterfly at idle. The large venturi begins to flow only if the throttle is opened maybe 25% or more (hard to test this on a trailer without over revving).

I wonder if perhaps the linkage between the carbs is misadjusted (not synchronized), so maybe the PTO carb butterfly is not in the correct position (closed more than the MAG carb butterfly).

Attached drawing shows all three of the possible fuel flow paths (idle port, Bypass Ports (AKA: Transition ports), Main Venturi) The main venturi doesn't flow until there's a load on the engine while in the water b/c the throttle needs to be open some amount to increase the velocity of air across that big venturi.

How about the main venturi mylar check valve (circled in blue) held by a single screw on the kidney shaped metering plate, it's not bent is it? If the mylar piece doesn't seal flat over the hole and against the metering plate you might experience no fuel at idle speed b/c air will come backwards from the Main Venturi into the metering chamber thus the metering valve might not pop and allow fuel into the chamber at idle.

Also keep in mind, fuel is provided on demand based on vacuum, the metering diaphragm doesn't move inward into the metering arm and pop the inlet valve open unless there's a vacuum signal. If the mylar check valve is damaged then there might not be enough vacuum to operate the metering diaphragm at low speed (such as idle).

 

[Sportster-2001-951C-Stock]

i can see fuel in the mag carb but none in the pto carb.

I didn't have the blue lines and could not see any curvature on the valves when I put them on a mirror, so I just installed them using the dental floss method which worked great.

It seems to be not getting fuel to the cylinder. The pto and mag carb both had fuel in it.

Actually, you can expect to see some fuel wetness in the carb bore while idling, even a small amount can sometimes spit back out is kinda normal on many 2-strokes. But!!! I wonder if you are certain the problem is on the PTO, ie:too dry, is it possible the MAG is too wet of fuel and it's missing(not firing) from being too rich???? Just had to ask that... Feel the spark plug for a bit of heat, the cold one will be the one that's not firing.

If the fuel chamber under the metering diaphragm was full of fuel on both carbs then the metering is working, look for a plugged idle passage, and or "bypass holes" might be blocked with corrosion or dirt.

The idle passage is fed by fuel passing through the small brass jet AND then the idle mixture screw, the bypass ports are fed with fuel passing through the small brass jet. If something was stuck inside the small brass jet, all of the low speed circuit would be shut off and no fuel at low speed.

As far as the check valves go, the curvature is due to the mylar film is rolled onto a roll in the manufacturing so it takes that curved shape when punched from the sheet. Some will be curved more than others depending on if it's tightly rolled on the inside or less curvature on the outer parts of the roll of film.

So, if you couldn't see the curvature while lying on a flat plate then I'd say don't sweat it, pour some liquid fuel into the chamber while it's apart and see if it quickly leaks out past the valve seat. A tiny seep is probably okay.

 

[powerslave]

I want to thank everyone for their help and time. Very nice of you all. Trying to diagnose this is draining my time. I would be interested if anyone would like to be paid to get these carbs working. Who should i speak with? I hate carbs! lol

 

[CReynoldsMIZ]

[MENTION=71806]Waterluvr[/MENTION] i think is his name. he does them i believe

 

[powerslave]

On my PTO carb here in the pic, is there supposed to be any other gasket?

 

[powerslave]

I'm at a loss. Fuel getting to mag carb, fuel getting to pto carb but fuel not getting to pto cylinder.

 

[Sportster-2001-951C-Stock]

Red(Low speed idle circuit) in this drawing is the fuel path inside the carb during idle. Red + Green (Low speed + transition circuit) is the flow path during part throttle. Red + green +Blue (high speed circuit) is the flow path at greater than ~30% throttle to wide open in water.

If you found there is fuel in the diaphragm metering chamber then it sounds like there must be an obstruction in the low speed idle/transition circuit.

Spraying carburetor cleaner from the can using the thin straw directly into the low speed jet should squirt out the bypass holes and low speed (idle) outlets. By "squirt" I mean squirt, not a mere dribble. If not, there is an obstruction. If this is good then there must not be fuel in the metering chamber (the metering needle isn't coming off it's seat to allow fuel into the chamber). The diaphragm is pulled by engine vacuum coming through the small passages and the diaphragm actuates the metering needle off it's seat.

If all that is good, is the vent hole in the metering diaphragm cover plugged with painters tape?

Is there a rag stuck in the intake manifold?

You can do this, I know you can.

 

[Sportster-2001-951C-Stock]

I don't notice anything unusual about your photo, looks like fuel can flow to the metering needle. I circled in red the path of fuel into the feed side of the carb and the green is the return to tank. You can see the restrictive orifice there in the return that helps maintain fuel pressure.

The small filter is where fuel enters and travels to the metering needle through that filter. Often those filters can plug with dirt and debris but it looks clean (I'm sure you cleaned it).

BTW, I always oil my screws, or put antiseize compound on the threads to lubricate the threads and reduce galling and corrosion.

 

[powerslave]

Ok, here is some new info. When starting, the mag carb shoots out fuel from the carb meaning back out of the carb like pressure is forcing it outside the carb while the pto carb dosent deliver fuel. Could this be a timing problem? Could it be the rotary valve needs adjustment?

 

[racerxxx]

Well, you only did a top end correct, so as long as you didn't pull the rotary valve cover your "should" be good, if it was a running ski before. Is it possible the RV was obstructed at any point during your rebuild and you turned over the engine? That could have possibly jammed the RV and stripped the gear, long shot I guess. Only thing you can do is either pull the carbs again and look at the RV or look thru the carb to see if it's moving. That still doesn't confirm it's in the correct position. The only time you would set that timing is when you physically remove the rotary valve, other than that it doesn't get adjusted.