Seadoo 717 hard start

[skrillac]

While working on a different ski (ski #2) that doesn't have this same hard start issue as the aforementioned jetski of this thread, I noticed some things. Went to clean ski #2's carbs, especially the low speed circuit and pilot jet as it was having problems idling. I took apart the jet side of the carbs, pulled jets out, cleaned, etc. I noticed that the springs for the needle valves were shiny silver (i think platinum). This is different from the 80 gram dark black spring I believe these 96 GTI 717's are supposed to have. I never took the springs out to measure length, but I did check popoff. Both carbs for ski #2 were very close. #2 PTO carb was 33-34psi. #2 MAG carb was 34-35psi. Ski #2 starts up everytime, never has problems. It didn't seem like there was any difference at all in the streams of brake clean spray flowing through the jets and carb holes while cleaning each set of carbs (ski #1 vs ski #2)

I think this may indicate my issue might be with the large variance in popoff pressure between the two carbs for ski #1. Currently I am still waiting on parts for ski #1. current popoff: ski #1 PTO carb 49-50psi. ski #1 MAG carb 39-41psi.

 

[mikidymac]

I agree, something is totally wrong, no way that pop-off should be that far apart.

 

[skrillac]

I was finally able to get the popoffs for the carbs closer together. Both carbs are now between 45-47psi. Tested each 10 times. I think some of the higher measurements here may have been inaccurate. Hence the multiple measurements.

PTO 46,47,46,45,45,45,44,45,47,47 avg 45.7
MAG 45,49,44,46,48,47,45,45,48,45 avg 46.2


Ended up putting a new lever arm, pin, screw, and 95 gram spring (p/n 270500313) in the MAG side carb.
Ended up putting a new lever arm, and 80 gram spring (p/n 270500267) in the PTO side carb. Had to bend the lever up a little bit.
Both carbs had new 1.2 needle/seats installed.

I should be getting the carbs put back onto the ski today. Will test later this week.

 

[mikidymac]

No, do not run them with 2 different springs in them. Not sure why the are reading so different but you never run two different springs.
Since everything is new just run them with the correct springs and see, don't chase pop-off.

 

[skrillac]

No, do not run them with 2 different springs in them. Not sure why the are reading so different but you never run two different springs.
Since everything is new just run them with the correct springs and see, don't chase pop-off.

I did try putting new 80 gram springs in each carb. Yielded PTO carb 49-50psi, MAG carb 39-41psi. Earlier this week I got another 80 gram spring, lever, lever pin, and lever screw. Installation into the MAG carb yielded the same 39-41psi. Threw in the 95 gram spring for the heck of it. Brought psi up about 5-6psi. Took the PTO carb and bent the lever up a small amount to bring its psi down. Both carbs are now between 45-47psi.

Why should it matter if the carb jettings are the same, needles are the same, popoffs are the same, but the springs aren't? The spring just resists fuel getting to the jets until the popoff pressure right? Only thing I could think would be a problem is if you cut a spring, then it would maybe be too stiff at top end of rpms. Is the concern here that using different springs would potentially lean out the high rpms, specifically in the carb with the stiffer spring? Couldn't I just turn its high speed screw out a bit to correct that?

I'm gonna try and run them with new plugs to see how things look afterwards. I'm at the end of my rope with these carbs on this ski. Either I fix them or find some that were rebuilt professionally. Does westside powersports rebuild these? Or should I just get a different set of carbs from them? My carbs came with the ski, but if I can't figure them out I'd prefer to just replace them.

 

[mikidymac]

No, because pop-off is just a test, it is not how the carbs actually work.
When running the rubber diaphragms actually push against the springs when vacuum is developed in the venturi of the carbs. So running two different springs is going to make one carb rich and one lean.
Again, if your ski calls for 80 gram springs and 1.2 needles and seats so that is what you run. Again stop chasing pop-off.
1.2 needles and seats with 80 gram springs should be 55 psi all the time everytime.

 

[skrillac]

No, because pop-off is just a test, it is not how the carbs actually work.
When running the rubber diaphragms actually push against the springs when vacuum is developed in the venturi of the carbs. So running two different springs is going to make one carb rich and one lean.
Again, if your ski calls for 80 gram springs and 1.2 needles and seats so that is what you run. Again stop chasing pop-off.
1.2 needles and seats with 80 gram springs should be 55 psi all the time everytime.

Idk why, but I was able to get the carbs set properly now. I guess I woke up on the right side of the bed this morning.
Both carbs now have the 80 gram springs, and 1.2 needle/seats.

PTO 45,45,47,46,48,47,46,46,46,46 avg 46.2 psi
MAG 47,46,46,47,46,46,44,46,45,46 avg 45.9 psi

Ended up swapping a few of those 80 gram springs (p/n 270500267) into the MAG side carb. I must have tried 2 or 3 of them. Eventually I found one that worked for me. Idk why that one worked, but the others didn't.
They don't have that perfect 55psi, but they are much better than before. And the popoffs are as close together as my other aforementioned ski.
Fingers crossed

 

[mikidymac]

Idk why, but I was able to get the carbs set properly now. I guess I woke up on the right side of the bed this morning.
Both carbs now have the 80 gram springs, and 1.2 needle/seats.

PTO 45,45,47,46,48,47,46,46,46,46 avg 46.2 psi
MAG 47,46,46,47,46,46,44,46,45,46 avg 45.9 psi

Ended up swapping a few of those 80 gram springs (p/n 270500267) into the MAG side carb. I must have tried 2 or 3 of them. Eventually I found one that worked for me. Idk why that one worked, but the others didn't.
They don't have that perfect 55psi, but they are much better than before. And the popoffs are as close together as my other aforementioned ski.
Fingers crossed

Now this is great news, finally!

 

[JJ1951]

Last year I had the 96 gti out on the lake. I took it over to a friend's dock, and shut it off for a few hours. Then it wouldn't start. Ended up discharging the battery trying to get it to start again. Finally was able to start it again after charging the battery up.

I rebuilt this ski a few years ago. Completely went through the fuel system. Osd Marine carb rebuild kits, new mpi grade fuel lines, new fuel selector, new check valves/relief valves for fuel system. I set carbs by the book. I believe when I measured popoff after rebuilding the carbs I got 40-42psi for each carb. I also did a top end and replaced the rotary valve and cover. Top end was from fullbore. Rotary valve and cover replacement came from sbt.

Whenever I put the ski away I fog the cylinders and either clean or replace spark plugs. Then once a year I winterize. Whenever I take the ski out it starts everytime. It may take a bit longer than my other 717, but it's not that noticeable. Now that I think about it, I do normally have to pull the choke and give a little throttle for awhile to start cold. But after it's warm, it's really hard to start after it's been shut off.

From the manuals troubleshooting section, it says to check rotary valve clearance and timing for hard starts. Today I performed the 45 degree feeler gauge test on both sides. Removed the valve cover oring, put the cover back on and torqued to 15lbft. Spec is 0.010 - 0.014in . On both sides of the cover, I am probably somewhere between 0.012 and 0.013 in. I know for certain I wasn't able to fit 0.014 in, so I don't think my clearance is bad. I'm gonna check the valve timing angle again.

Is there anything else to check that would cause this hard start when warm?

Last year I had the 96 gti out on the lake. I took it over to a friend's dock, and shut it off for a few hours. Then it wouldn't start. Ended up discharging the battery trying to get it to start again. Finally was able to start it again after charging the battery up.

I rebuilt this ski a few years ago. Completely went through the fuel system. Osd Marine carb rebuild kits, new mpi grade fuel lines, new fuel selector, new check valves/relief valves for fuel system. I set carbs by the book. I believe when I measured popoff after rebuilding the carbs I got 40-42psi for each carb. I also did a top end and replaced the rotary valve and cover. Top end was from fullbore. Rotary valve and cover replacement came from sbt.

Whenever I put the ski away I fog the cylinders and either clean or replace spark plugs. Then once a year I winterize. Whenever I take the ski out it starts everytime. It may take a bit longer than my other 717, but it's not that noticeable. Now that I think about it, I do normally have to pull the choke and give a little throttle for awhile to start cold. But after it's warm, it's really hard to start after it's been shut off.

From the manuals troubleshooting section, it says to check rotary valve clearance and timing for hard starts. Today I performed the 45 degree feeler gauge test on both sides. Removed the valve cover oring, put the cover back on and torqued to 15lbft. Spec is 0.010 - 0.014in . On both sides of the cover, I am probably somewhere between 0.012 and 0.013 in. I know for certain I wasn't able to fit 0.014 in, so I don't think my clearance is bad. I'm gonna check the valve timing angle again.

Is there anything else to check that would cause this hard start when warm?

Just wanted to pass along my experience. I've a 96 Speedster and could not keep it running nor get the RPMs past 3000 before dying. Irebuilt the carbs, cleaned filters etc. Was able to run it slowly. Took it to two mechanics with no luck. The second said he would pull the engine during the off season. He called me around Thanksgiving to tell me while disconnecting the exhaust to pull the engine he found a mouse nest packed so tight it took an hour to pick it out! The boat has worked great since. Just a thought.

 

[skrillac]

Now this is great news, finally!

View attachment 68431

Got the ski back together. Put new BR8ES plugs in. The ski was STILL as difficult to start as before. . No choke, slight throttle (~25%) was finally able to start it. It didn't start immediately, had to hold the throttle at that position for a few seconds after the engine started to get up to operating rpms. I made some final idle speed adjustments to bring the rpms up a bit and rode around for 20-30 minutes idling. Brought the ski back to the dock and took the plugs out. The photos labeled 'MAG' and 'PTO' were taken of the corresponding spark plugs. Put the plugs back in and took the ski out again to test the rest of rpm range. Ran great.

Took ski #2 out as well. It had its carbs cleaned recently (and it's PTO carb low speed screw turned in from 1.75 turns out to 1.25 turns out, like the manual says) and new BR8ES plugs put in. I idled it for the same time period 20-30 minutes and came back to the dock so I could get some pictures to compare to. The photos labeled '#2 MAG' and '#2 PTO' were taken of the corresponding spark plugs. Put the plugs back in and took the ski out again to test the rest of rpm range. Ran great.

It seems that ski #1 (the subject of this thread and the hard to start ski) had a slightly harder time keeping idle. That is to say it's idle jumped from anywhere between 1390-1550 rpm. When it was just idling in the beginning, it's idle was between 1490-1550rpm. After I took it out to test high rpm range, after 30 seconds of full throttle I let it idle again and it idled a bit lower at 1390-1450rpm.

Ski #2 pretty much kept idle consistently at 1550rpm. I'd come off full throttle and it would fall immediately to 1600rpm, then trickle down back to 1500-1550rpm.

I think I'm still running a bit rich at low rpms for ski #1. It seems like it's 0-25% throttle range has a small amount of hesitation. It doesn't bog per say, but it isn't as crisp as ski #2. Previous to creating this thread, I had low speed screws set on ski #1 to 1.00 turns out from closed and it still ran this way. Same method of starting too, no choke tiny amount of throttle. I'm thinking I may turn the low speed screws in 3/8 of a turn from where they are now at the stock 1.25 turns out setting and putting a new pair of plugs in, for additional testing purposes.

@mikidymac In your expert opinion, what do these plugs say about how the respective skis are running at bottom end rpms?

 

[mikidymac]

Idling for 20-30 minutes is not good. These will load up and foul plugs idling that long. Get them out and run them.

 

[skrillac]

Idling for 20-30 minutes is not good. These will load up and foul plugs idling that long. Get them out and run them.

Yeah i probably did idle too long. How long should I have idled to then pull plugs and check for color to determine how I'm running at idle?

And do you agree with my tuning assessment? Turning the low speed screws in 3/8 of a turn on ski #1?

 

[mikidymac]

Plug read at idle will really do nothing.
If it idles fine and transitions from idle well then youa re good.

Never change more than 1/8 turn at a time. Always go richer first.

Here it the proper procedure to set the LS screws, they only affect idle.


"The idle drop test is how I have been tuning a carburetors low speed and pilot circuits since the early
1980's. The only thing that has changed is the the adjustment after the engine dies or wants to die.
On early Mikuni BN carbs the adjustment is 1/4 turn. But when the CDK II was released in 1986, the
adjustment was increased to 1/2 turn. The same 1/2 turn adjustment works for the Mikuni SBN, SBN-i
carbs. The reason for this change was the manufactures started using an fuel-air pilot circuit on the
CDK II, SBN, SBN-i carbs. The BN has a traditional low speed circuit.

A very common loss of peak performance is caused by the low speed (pilot) screw set richer than
necessary.

With the idle drop test you can determine if the low jet and spring is the correct size. On the the CDK II,
SBN, SBN-i carbs, the low jet, spring, seat diameter, and low speed (pilot) screw are all inter-connected.

Using the idle drop test rules, I was able to develop reverse jetting with a very high pop-off, using seats
from 1.2 to 2.0 and pop-off 32, 55, 76 psi. It is the style of jetting I prefer for all SBN, SBN-i carbs from
increasing the performance of stock engines to full race engines. But it does not work on carbs with
modified low speed by-pass holes (like Novi).

The only type of carbs I would not use this test on is the Novi, or any carb with a modified return line
circuit. Otherwise it works on all diaphragm carbs including weed whackers.

Idle drop test
Perform the idle drop test in a test tank, a trailer, or secured to the shore line. Set the pilot screws set to
some arbitrary rich setting. For example: 1 ½ turns out, and warm up the engine. Set the idle to a low
rpm. A good rule of thumb: You should be able to hold your hand behind the pump. If the pump pushes
your hand away, the idle is too fast.

Slowly turn the pilot screw(s) inward (clockwise) until the engine wants to die, or quits. Make a note of
how many turns it takes to bottom the screw(s). It will be easier to shut the engine off (when the engine acts
like it is about to lean out and die) yourself and make the adjustments, and document turns to bottom or
closed. Next, reset the low speed (pilot) screws to the setting where the engine died, and turn the low speed
(pilot) screw(s) outwards an additional ½ turn. Restart the engine, and recheck the idle. If the engine rpm
increases, and you can no longer hold your hand behind the pump, I recommend readjusting the idle and
the pilot screw again.

Next, test the acceleration and make note of any strange behavior or tenancy to quit on deceleration. Shut
the engine off and turn the pilot screw inwards until they lightly bottom. Make note of the number of turns
in. I count screw settings in half turns, use whatever method to count screw settings that suits you. Then write
the settings down and keep it for latter, and reset the screw(s) position.

I normally strive to achieve ¾ turns out on the pilot screw, and if the engine begins to die at ¼ turns out,
I consider that perfect. If the engine is still running and the pilot screws are closed, this is a sign the low
speed jets are too rich. In this case I would recommend leaning the low jet 2 sizes. If the pilot screw position
is at 1 turn out, that is a sign the low speed jet is too lean. Another rule of thumb is to use ¼ turn = 1 pilot jet
size. In this case I would recommend caution and only change the jet two sizes richer, and then retest."


Bill M.

 

[skrillac]

Plug read at idle will really do nothing.
If it idles fine and transitions from idle well then youa re good.

Never change more than 1/8 turn at a time. Always go richer first.

Here it the proper procedure to set the LS screws, they only affect idle.


"The idle drop test is how I have been tuning a carburetors low speed and pilot circuits since the early
1980's. The only thing that has changed is the the adjustment after the engine dies or wants to die.
On early Mikuni BN carbs the adjustment is 1/4 turn. But when the CDK II was released in 1986, the
adjustment was increased to 1/2 turn. The same 1/2 turn adjustment works for the Mikuni SBN, SBN-i
carbs. The reason for this change was the manufactures started using an fuel-air pilot circuit on the
CDK II, SBN, SBN-i carbs. The BN has a traditional low speed circuit.

A very common loss of peak performance is caused by the low speed (pilot) screw set richer than
necessary.

With the idle drop test you can determine if the low jet and spring is the correct size. On the the CDK II,
SBN, SBN-i carbs, the low jet, spring, seat diameter, and low speed (pilot) screw are all inter-connected.

Using the idle drop test rules, I was able to develop reverse jetting with a very high pop-off, using seats
from 1.2 to 2.0 and pop-off 32, 55, 76 psi. It is the style of jetting I prefer for all SBN, SBN-i carbs from
increasing the performance of stock engines to full race engines. But it does not work on carbs with
modified low speed by-pass holes (like Novi).

The only type of carbs I would not use this test on is the Novi, or any carb with a modified return line
circuit. Otherwise it works on all diaphragm carbs including weed whackers.

Idle drop test
Perform the idle drop test in a test tank, a trailer, or secured to the shore line. Set the pilot screws set to
some arbitrary rich setting. For example: 1 ½ turns out, and warm up the engine. Set the idle to a low
rpm. A good rule of thumb: You should be able to hold your hand behind the pump. If the pump pushes
your hand away, the idle is too fast.

Slowly turn the pilot screw(s) inward (clockwise) until the engine wants to die, or quits. Make a note of
how many turns it takes to bottom the screw(s). It will be easier to shut the engine off (when the engine acts
like it is about to lean out and die) yourself and make the adjustments, and document turns to bottom or
closed. Next, reset the low speed (pilot) screws to the setting where the engine died, and turn the low speed
(pilot) screw(s) outwards an additional ½ turn. Restart the engine, and recheck the idle. If the engine rpm
increases, and you can no longer hold your hand behind the pump, I recommend readjusting the idle and
the pilot screw again.

Next, test the acceleration and make note of any strange behavior or tenancy to quit on deceleration. Shut
the engine off and turn the pilot screw inwards until they lightly bottom. Make note of the number of turns
in. I count screw settings in half turns, use whatever method to count screw settings that suits you. Then write
the settings down and keep it for latter, and reset the screw(s) position.

I normally strive to achieve ¾ turns out on the pilot screw, and if the engine begins to die at ¼ turns out,
I consider that perfect. If the engine is still running and the pilot screws are closed, this is a sign the low
speed jets are too rich. In this case I would recommend leaning the low jet 2 sizes. If the pilot screw position
is at 1 turn out, that is a sign the low speed jet is too lean. Another rule of thumb is to use ¼ turn = 1 pilot jet
size. In this case I would recommend caution and only change the jet two sizes richer, and then retest."


Bill M.

Is this worth doing to fix my issue with hard starts (no choke, 25% throttle)? The ski idles fine as things are now.
Also, if I do attempt this what is the context of these numbers? Low speed setting for my ski is 1.25 turns out from closed. This talks about 0.75 turns out. Do these pilot jet references apply to me as well? 1/4 turn = 1 pilot jet size

From reading this I gather this process

1. Launch the ski and tie off to dock. Bring the idle down really low to the point where i can hold my hand behind prop.
2. Turn low speed (pilot) screws in on both carbs until the engine wants to die
   • I'm only able to adjust one carb's low speed screw at a time. If the engine starts to die after I make adjustments to one carb, I'm assuming that I'd match the adjustment to the other. So if I turned the screw in 1/2 turn (from where they are now at -1.25) on the first carb and the engine dies, I'd set the other carb there too.
3. Once I've found the point where the engine dies, turn the pilot screws in until they bottom out and record number of turns.
4. Turn the pilot screws out back to where they were, and back them out an additional 1/2 turn
5. If the engine rpm stays the same and i'm still able to freely hold my hand behind prop, i've correctly set the pilot screw.