Weird carb setting question

[PRAIRIEOUTLAW]

I bought a 96 seadoo gtx and have run into something that makes me think I have a problem beyond carb settings. The compression is good, in fact it WAS a bit high but I'm sure that was due to sitting for a prolong period of time cause when it first fired off it smoked like the woods were on fire.
Anyway, I cleaned the carbs and did a rebuild. Everything is clean. Small jets and all. Set carb to spec at 1 turn slow speed and fully closed high speed. Took it out and it started. I adjusted the low speed and idle to get it right there. All was good. Then had the stumble when you go closed throttle to full throttle. It would pick up but I was sure it was lean on the high speed jet. Pulled the new plugs and checked and sure enough way lean so I turned the high jets to like 1/8 and checked and still really lean. After adjusting them to like 1 and 1/8 turn out it picked up ok but the back cylinder was still lean so I turned just it and I got it smoothed out and it's running pretty good and plug test looks good. I've never seen one be set different. Any thoughts or am I just worrying?
I was thinking an air leak somewhere but not sure. Any suggestions. Thanks in advance.

 

[Coastiejoe]

Do you still have the Grey Tempo Furl lines on the ski?

 

[Mekanix]

Fuel lines
fuel selector
Water separator/fuel filter
That thing should run good with the high speeds all the way in.


Air leaks could be:
Crank seals leaking
Carb manifold gaskets
Rotary valve seal.

 

[PRAIRIEOUTLAW]

All fuel lines have been replaced. Selector and filter have been cleaned. Most parts inside the carbs are new. Like I said. It runs ok like it is but the hs jets are turned way up and aren't set the same. Only thing I can think that could be the problem is the pop off. I replaced the spring with the same color when rebuilding the carbs and didn't have a tester at the time. Ordering one to to tonight.

I guess this could possibly be the problem but doesn't make sense why the jets wouldn't be the same unless the popoff is that much different between the two carbs. Either way just wanna get it right.

 

[Mekanix]

You can build a tester for less than $15.
Pop off does not matter to the top end jetting.

Once you hit 4000 or so its already into the main jet.

Pop off is only efective up to 1/3 throttle.
Unless your pop off is extremely high, as in: 70+psi I don't feel that is the problem.

This is the 787 engine right?
Are you using the airbox ?
What numbers are on the high and low jets?


While your in there. Change the oil for the balance shaft just to be safe.

 

[Pointhunter75]

When i put my carbs back together other day and put the high and lows back in the carbs and screwed em all the way in to back em out, one of them didnt lline up the same as the other carb. The T needles, one was straight up and down but the other carbs T needle was about a quarter turn different. That normal?

 

[Mekanix]

When i put my carbs back together other day and put the high and lows back in the carbs and screwed em all the way in to back em out, one of them didnt lline up the same as the other carb. The T needles, one was straight up and down but the other carbs T needle was about a quarter turn different. That normal?

Could be just that screw or just that thread in the carb that is different. As long as its not bent or brokenor worn and it seats properly your good.

 

[Sportster-2001-951C-Stock]

It would be highly abnormal if the head positions lined up, adjustable orifice size is directly proportional to turns open from lightly seated and is the suggested starting point.

These settings are applicable if you still have all the original equivalent parts in the intake airbox, such as factory flame arrestor and enclosure, otherwise it will likely be necessary to make adjustments to compensate for aftermarket filters.

You're better off adjusting the carb as necessary to avoid a lean condition which can damage the engine but those settings should be very close to the suggested settings and if not, there's a good chance something's not right(such as airbox was removed).

 

[Pointhunter75]

Thanks just making sure. All stock.

 

[PRAIRIEOUTLAW]

You can build a tester for less than $15.
Pop off does not matter to the top end jetting.

Once you hit 4000 or so its already into the main jet.

Pop off is only efective up to 1/3 throttle.
Unless your pop off is extremely high, as in: 70+psi I don't feel that is the problem.

This is the 787 engine right?
Are you using the airbox ?
What numbers are on the high and low jets?


While your in there. Change the oil for the balance shaft just to be safe.

K I've ordered a tester and its on the way.

Here is a bit more info. The unit is completely stock. It's been several weeks since I was in the carbs doing the rebuild so don't remember the jet numbers now but seems like I checked em and both were stock size. I rebuilt the carb with everything new except for needle valve. Even put new spring on the arm but used the same length/color as was in it.

I understand the basic operation of the carbs and am pretty good at adjusting. Our family has 4 of these gtxs and I've turned a lot of wrenches so not a total newbie just can't seem to figure this out if its not the popoff.

What I'm thinking is the pop off is too high or maybe too low and its causing that 3/8ths throttle stumble that happens when you go from closed throttle to full throttle. (Basically either starving for fuel shortly or way rich for a short time)
When it gets up on plan and above the 4k rpm it does fine, so that says the wide open circuit should be ok. But why is it that the adjustments are so far out to get a clean plug test instead of being around fuller closed on the high speed jets? I know that's just a starting point, but aren't they usually close? And shouldn't they both be real close to the same (front and back cylinders)

 

[Sportster-2001-951C-Stock]

K I've ordered a tester and its on the way.

Here is a bit more info. The unit is completely stock. It's been several weeks since I was in the carbs doing the rebuild so don't remember the jet numbers now but seems like I checked em and both were stock size. I rebuilt the carb with everything new except for needle valve. Even put new spring on the arm but used the same length/color as was in it.

I understand the basic operation of the carbs and am pretty good at adjusting. Our family has 4 of these gtxs and I've turned a lot of wrenches so not a total newbie just can't seem to figure this out if its not the popoff.

What I'm thinking is the pop off is too high or maybe too low and its causing that 3/8ths throttle stumble that happens when you go from closed throttle to full throttle. (Basically either starving for fuel shortly or way rich for a short time)
When it gets up on plan and above the 4k rpm it does fine, so that says the wide open circuit should be ok. But why is it that the adjustments are so far out to get a clean plug test instead of being around fuller closed on the high speed jets? I know that's just a starting point, but aren't they usually close? And shouldn't they both be real close to the same (front and back cylinders)

'96 GTX Specs are here for the purposes of our discussion:

"www.seadoosource.com/carbreference.html"

"stumble when you go closed throttle to full throttle."

Could go in a few directions on this problem description depending on if carb(s) are equipped with accelerator pump(s), a stumble could be many things, even a normal phenomenon, depending on how prevalent and whether a momentary rich or lean condition. I would reconfirm all the carb calibrations and start from scratch.

"lean so I turned the high jets to like 1/8 and checked and still really lean. After adjusting them to like 1 and 1/8 turn out it picked up ok"

These should be closer to "0" from lightly seated, what size are the metering needle seat orifices?

It's hard to know the history of your carb(s) unless everything is documented, such as metering seat size, pilot jet and high speed jet size, metering spring weight, and pop-off measurement. Depending on these calibrations, it may be necessary to open the high speed mixture screws some amount.

A thorough carb rebuild should include a replacement metering needle/seat IMO. If this were my ski, I would replace them if they hadn't been recently. There are several different size n/s's available depending on how you are tuning your carb, the factory suggested orifice size would be my choice if the ski wasn't being built for competition racing with oversized bore, sodium filled piston skits, sneeze through wind vents, starch on mud guards and performance modified rings.