Its me again!

[mh_rogers]

This an update of the issue I have with my 95 seadoo gts. It has a rebuilt 580 with just a few hours on it. I rebuilt the carb myself before I put the new engine in. It also has a coffman's performance exhaust on it. On the water in a straight line, it runs really good. It tops out at about 40 mph. I figure that's pretty good for a 580. Engine is really smooth and idles good. Throttle response is decent. However, the moment I dive into a turn at full throttle the power dies off to the point you think it will shut off. The moment the boat levels off, the boat still has a brief "flat spot" and then power returns. I checked the plugs after my last outing and I noticed that the threads looked a little wet with fuel, and the plug tip was black but did not wet with fuel.

With that info, I turned the high speed screw all the way back in and then back it out by about 1 -1 1/4 turn, hoping to lean it out some. The previous setting was more like 2+ turns out, so it probaly was way rich. Still after making those adjustments the problem still exsists. The adjustment seemed to have no affect whatsoever.

I was told by my mechanic that the boat is running very rich and that the source of the problem could be the preformance pipe as it is not warming up as it should. However I checked my pipe on my gtx after the same run and the temps feel to be about the same. On both skis the pipes are almost cool to the touch. I am not convinced that the pipe is the problem.

I suspect the problem is something wrong with the carb itself or could it be an issue with the wear ring. I have checked it and other than some minor abrasion it seems to be okay. What do you think?

 

[robin savell lloyd]

I thought that the high speed screw was suposed to be at 0 or close to being closed. but I can be wrong

 

[mh_rogers]

0 or close to zero?

Well, that just might be my problem. Going to the lake to give it a try and see what happens. I was scared to go zero for fear of leaning it out. While im at it what about the low speed adjustment. It has the factory plastic cap which limits adjustment pretty much to up or down. Which is it?

 

[robin savell lloyd]

you may want to hold off. one of us has it backwards I thought the the one with the cap should be the high speed adjustment. low speed should be close to 1 1/4 turns out.

 

[seadoosnipe]

High speed screw.....

You are very correct in that Robin. There is suppose to be a black cap on that high speed screw, that is only adjustable by about 1/4 turn. If someone has removed it, then going to zero could endager your mixture. The term in the manual, high speed at zero, refers to the needle valve setting, provided that black cap is still on.
And your correct on the low speed screw Robin.
The only thing I can add, is that if you changed the exhaust system, 9 times out of 10, you have to re-jet your carbs. Unless the performance output from the resonated exhaust is the same flow, then you wouldn't have to change. But if your flow rate is higher, then you have to re-jet. Remember, an exhaust system is designed to always have a small amount of back pressure.
Compare the specs to your old and new exhaust. That will tell you. Or if your running a stock Mikuni 38, then re-jet the next size up.

 

[mh_rogers]

Thanks Guys

Thanks a ton to everyone for the very helpful and timely info.
I think I will take it to a dealer for this procedure. I did run it for a little while with the "screws in". The black plastic cap is still on the high speed screw. (It was my understanding this was the high speed screw.) This would not have harmed my motor in any way having run it at those settings? Did not seem to have affected it in any way that I could tell. Still bogged down in the turns like always.

With a rejet should I also consider a impeller change and if so what pitch, brand, etc., would you reccomend?

 

[robin savell lloyd]

Mh rogers please let us know if you find the performace problem so we may let others know what they may need to look for. I have a probem that seems like yours but have not had the time feeling good enough to trouble shoot it yet. so it may even help me. good luck. robin

 

[kustomkarl]

Mh rogers once you get it running good, than go and change the impeller. If you go to www.solas.com it will have a chart of impellers available. Typically the impeller will not cause the seadoo to run like it is. It needs to be re- jetted before you do anything else to it. Go up 1 size as seadoosnipe said, than check on the plug readings to see it isn't too rich in the complete throttle range. The low speed screw only adjusts the idle to mid range speed, than the high speed screw adjustment takes over from there. Leave the high speed screw at "0" and the low speed starts at 1 1/4 and adjust from there.
Let us know how you make out.

Karl

 

[mh_rogers]

Thanks again!

Thanks for all of the advice will be getting the carbs rejetted within the next week or so. Can't wait to get this straightened out as I really do want to keep the performance exhaust. Seeing as how it will spend most of its time chasing the GTX that my wife rides, I am wanting to get as much power out of this little mill as possible. Robin, my prayers are with you that you will start feeling better soon. There are precious few other things that make me feel better than blasting down the lake on my 'ski!