Super Jet 07 Superjet stumbles @ 1/4 Throttle

[fharrison]

I am a bit stumped. I have a stock 07 Superjet that has been running well all spring and summer. Took it out on a couple mile run to the local sand bar and it ran great all the way there. Stopped for a while and rode around occasionally once I got there. It was running great and all of a sudden would start to stumble around 1/4 throttle then if I pumped the throttle a little, it would take off. Very difficult to ride when it stumbles/dies riding slow. The only thing I did differently was use cheap SuperTech oil from Walmart because it was all I had around unfortunately. Could that be an issue? There was also a LOT of floating seaweed that required clearing of the intake grate every so often. I dont know if that could be an issue with clogging. The pisser was always flowing. Engine was hot but not water sizzling hot.

Cleaned the carb at the beginning of this year. Little bit of gunk but not bad at the time. The ski has stock jets, pop off is 53 psi and I replaced the large external fuel filter a couple of weeks ago. From my searching around, I thought it could maybe be the spark plug terminals but I am not sure. I took the plugs out after I got home and they looked almost too clean. What do you think? Left is the rear cylinder, right is the front cylinder.

 

[jdmforlife]

Try some new plugs

 

[Matt_E]

The needles (of the needles & seats in the carburetors) are probably starting to wear and need to be replaced. But yeah, replace the plugs first.

 

[fharrison]

I will give new plugs a try. Thanks for the help.

 

[Vumad]

The needles (of the needles & seats in the carburetors) are probably starting to wear and need to be replaced. But yeah, replace the plugs first.

Can't be that unless he checked the pop off wrong??

 

[Matt_E]

Checking popoff may not always be a good indication of a worn needle. But generally, I would expect to see inconsistent and creeping popoff rather than crisp popoff with a worn needle.

 

[fharrison]

When I cleaned the carbs this year, I was using a pop off pump and it was a crisp pop. Tested each one at least 3 times to make sure the readings were accurate.

 

[IS0LD0UT]

Matt, how long do you run a needle and seat before it usually is worn?

 

[Matt_E]

I think 3-5 seasons.

fharrison: With your description of the popoff, I do not think that's the problem.

 

[Vumad]

I think 3-5 seasons.

fharrison: With your description of the popoff, I do not think that's the problem.

OEM/Mikuni or SBT?

 

[Matt_E]

OEM only.