Carb issues 2000 seadoo GTI

[dabernathy8181]

2000 seadoo GTI, just rebuilt the carb because the motor was getting a little boggy on restarts. I believe I know what the culprit is but I wanna see if others have the same opinion. So the ski cranks a little slow when it's cold, but will idle perfect once it cranks. Once the initial crank happens it cranks perfect as well. I've done the carb adjustments and the mocha brown color is what I have finally landed on. Now here is the head stomper. If I give it full throttle it jumps out of the hole like a rocket ship and runs perfect. But if I barely give it any gas it bogs down and dies out. I thought that there was possibly an airleak near the carb mount causing this after reading a thread on here so I pulled the carb and replaced the gasket. The pto cylinder was overly oily/black but the mag cylinder was showing perfect on the plug. Now I am leaning towards an issue with the internal fuel pump not being able to generate enough pressure at low speed but it overcomes it at high speed acceleration. I used all Mikuni rebuild parts, went down that road before with aftermarket vortex kits and chased an issue for the better part of 2 months, plastic parts were to thick. So am I off my rocker in thinking the fuel pump? I installed the diaphragm correctly but may have deformed it when installing the little black rubber piece cause they are a doozy. I have not checked compression recently, ski only has 150ish hours on it but leaning away from that.

 

[burtshaver2021]

You can test the fuel pump. There are 2 tests for it in the manual. Better than throwing parts at it

 

[etemplet]

I'd look at the transition circuit. Might be as simple as opening up the low speed adjusters 1/2 turn to see what happens.

When you hammer the throttle the carb can quickly run on the main jets which pretty much nothing else needed. Accelerate slowly and the carb will have to transition from low speed to intermediate to main. Running well at full throttle tells me you don't have fuel delivery problem so I wouldn't look to the fuel pump to solve any problem. If setting the low speed adjusters does not have the desired effect I'd make sure the 4 holes in the barrel of the carb are not restricted. I test mine with lectra-kleen. They should spray forcefully. (remove the low speed jet, insert the small red tube into the jet orifice and spray... look into the barrel of the carb). Plug the big hole with your thumb. the low speed adjuster must be in place but I loosen it quite a bit. Good Luck.

The way you describe the problem tells me you are lean on the low speed. Also you can check the "check valve" under the carb block and make sure it is sealing well.

 

[burtshaver2021]

I'd look at the transition circuit. Might be as simple as opening up the low speed adjusters 1/2 turn to see what happens.

When you hammer the throttle the carb can quickly run on the main jets which pretty much nothing else needed. Accelerate slowly and the carb will have to transition from low speed to intermediate to main. Running well at full throttle tells me you don't have fuel delivery problem so I wouldn't look to the fuel pump to solve any problem. If setting the low speed adjusters does not have the desired effect I'd make sure the 4 holes in the barrel of the carb are not restricted. I test mine with lectra-kleen. They should spray forcefully. (remove the low speed jet, insert the small red tube into the jet orifice and spray... look into the barrel of the carb). Plug the big hole with your thumb. the low speed adjuster must be in place but I loosen it quite a bit. Good Luck.

The way you describe the problem tells me you are lean on the low speed. Also you can check the "check valve" under the carb block and make sure it is sealing well.

Yea, what he said

 

[dabernathy8181]

I'd look at the transition circuit. Might be as simple as opening up the low speed adjusters 1/2 turn to see what happens.

When you hammer the throttle the carb can quickly run on the main jets which pretty much nothing else needed. Accelerate slowly and the carb will have to transition from low speed to intermediate to main. Running well at full throttle tells me you don't have fuel delivery problem so I wouldn't look to the fuel pump to solve any problem. If setting the low speed adjusters does not have the desired effect I'd make sure the 4 holes in the barrel of the carb are not restricted. I test mine with lectra-kleen. They should spray forcefully. (remove the low speed jet, insert the small red tube into the jet orifice and spray... look into the barrel of the carb). Plug the big hole with your thumb. the low speed adjuster must be in place but I loosen it quite a bit. Good Luck.

The way you describe the problem tells me you are lean on the low speed. Also you can check the "check valve" under the carb block and make sure it is sealing well.

Thanks for the replies, I have played with the low speed adjustments, started 1.5 turns out and my pto cylinder was flooding out. Dropped it down to slightly more than 1 and the plugs were perfect, but I did go all the way out to 2.5 initially thinking the same thing, a lean condition.

Getting close to topend rebuild time most likely, (not the same issue but could be contributing). The carb is the OG carb going on 25 years old, second rebuild in about 5 years, learned my lesson with vortex carb kits(most everything is good but the fuel metering flap is to thick requiring the choke to be on to run), To start fresh I am probably going to throw another carb on it instead of another $100 rebuild kit.

 

[mikidymac]

I messed with mine for over a year and finally gave up and replaced the entire carb and it ran like nothing before, it was great!.
I have been in and out of these carbs for over 30 years and that one just stumped me.

 

[etemplet]

Thanks for the replies, I have played with the low speed adjustments, started 1.5 turns out and my pto cylinder was flooding out. Dropped it down to slightly more than 1 and the plugs were perfect, but I did go all the way out to 2.5 initially thinking the same thing, a lean condition.

Getting close to topend rebuild time most likely, (not the same issue but could be contributing). The carb is the OG carb going on 25 years old, second rebuild in about 5 years, learned my lesson with vortex carb kits(most everything is good but the fuel metering flap is to thick requiring the choke to be on to run), To start fresh I am probably going to throw another carb on it instead of another $100 rebuild kit.

yep without genuine Mikuni kits those carbs don't work very well.