SUPERJET LOSS OF FUEL

[jetskichik]

Hey everyone,
I have had a 96 superjet for years and never have i been able to jump a wake without the ski losing all fuel power. What do i need to look for? I have to feather the throttle to get the fuel back after i land....does the same thing when im turning a certain direction...doesnt matter if the tank is full either... dual mikuni carb, fuel filters on ALL lines including vent...help. thanks in advance

 

[Mike W]

When was the last time you had the carbs rebuilt?

 

[john zigler]

Could be many things wrong with your ski. By your description it sounds as if you are lean. Improper tune (jetting, etc), dirty carbs, fuel system needing attention, Air leak bad crank seals, etc. Or maybe even just needs to adjust the carb high/low screws.

Has it ever run correctly?

 

[Big Kahuna]

Also bad plug wires (Broken ends at the plug caps) can make it feel this way. Ski runs fine on flats, but when you jump, the wires start moving and they lose conductivity.

 

[Pro-pulsion]

Had this very thing happen to my GP760 and my long time ago Sea-Doo XP800. Time to replace the crank and seals and give it a proper rebuild. If it has never been done, it's due. That almost 30 year old engine has served you well to keep going this far without blowing up. The signs I got from my mentioned skis were...on the Sea-Doo it sometimes run ok but not great, sometimes not run in the water but run fine on the trailer and under hard acceleration the battery light would flash because the mag cup was scrubbing the stator. The evidence after a tear down was bad crank bearings. On the GP760, it ran great until a decent wave jump of about 5 feet then it would either shut down, act like it was boggy and had to feather the throttle until it came around, or it would start acting up under a mild to strong turn to which it would need to be throttle feathered until the crank balanced out in the sloppy bearings. It was a 97 with about 236 hours on it, the XP800 was a 96 with unknown hours on it but definitely had a manufacturing defect in the crank bearings, of the 6? ball bearings that it was supposed to have, the cage was missing 3. It apparently had been through about 3 dealships for the problems mentioned and none of them could find it... because none of them wanted to pull the motor out From my experience with these exact symptoms, it's all pointing to the crank bearings getting old and worn out allowing air in past the crank seals and significantly throwing off your air/fuel ratio making it very lean.

 

[jetskichik]

Could be many things wrong with your ski. By your description it sounds as if you are lean. Improper tune (jetting, etc), dirty carbs, fuel system needing attention, Air leak bad crank seals, etc. Or maybe even just needs to adjust the carb high/low screws.

Has it ever run correctly?

Hhhmm i literally just redid crankseals and havent had a chance to test it out...maybe that was the issue... i did replace all fuel lines while the ski was down. If there was one thing i was taught it was to tread lightly around these carbs when tuning...lol. sp terrified to mes with it. If im lean the plugs are on the whiter side correct? Thanks for replying

 

[jetskichik]

Had this very thing happen to my GP760 and my long time ago Sea-Doo XP800. Time to replace the crank and seals and give it a proper rebuild. If it has never been done, it's due. That almost 30 year old engine has served you well to keep going this far without blowing up. The signs I got from my mentioned skis were...on the Sea-Doo it sometimes run ok but not great, sometimes not run in the water but run fine on the trailer and under hard acceleration the battery light would flash because the mag cup was scrubbing the stator. The evidence after a tear down was bad crank bearings. On the GP760, it ran great until a decent wave jump of about 5 feet then it would either shut down, act like it was boggy and had to feather the throttle until it came around, or it would start acting up under a mild to strong turn to which it would need to be throttle feathered until the crank balanced out in the sloppy bearings. It was a 97 with about 236 hours on it, the XP800 was a 96 with unknown hours on it but definitely had a manufacturing defect in the crank bearings, of the 6? ball bearings that it was supposed to have, the cage was missing 3. It apparently had been through about 3 dealships for the problems mentioned and none of them could find it... because none of them wanted to pull the motor out From my experience with these exact symptoms, it's all pointing to the crank bearings getting old and worn out allowing air in past the crank seals and significantly throwing off your air/fuel ratio making it very leaoh wo

 

[jetskichik]

Oh wow you were definately experienxing the same as me. We had the cranl out and bearings were all good just the rear seal blew out so replaced them all so im really hoping that was the issue. Thank you for your reply

 

[Pro-pulsion]

I have had just the seal in the pto side go funny before too, same symptoms but just a bad seal. I did the same thing as you and replaced the crank seals along with the obvious of course, crankcase sealant and gaskets etc. But that did cure the problem for me. Keep in mind this happened on my new at the time crank so yes, even seals alone can go funny shortly after being new. Since I redid the crank seals I have logged well over 100 hours of operation without any further issues