Won’t reach high rpm


Hi guys, I am still working on my 92 xp, and it finally runs in the water.
But now there is another problem it does not reach above 3600 rpm.
I already rebuild the carbs with oem kits and I set the pop off on 25 psi, (not with an official pop-off pressure tester.) But i think it has to do something with fuel.
These are the symptoms:
in water:
The ski only reach 3600 rpm with choke 1/4 closed.
after it reached 3600 rpm you can let the choke down and it stays at 3600 rpm
If you go full throttle without choke it goes off.

out of the water:
It backfires continuely arround 4500 rpm

There are also sometimes air bubbles in the fuel lines.
What could this be?
I appreciate your help.

With kind regards Elster


Well-Known Member
I'd get a mitey-vac pump and pull the vacuum on the fuel system from the carb inlet hose. You could have a very common leak on the water separator. could be your fuel selector is leaking. I bought a pump that pulls vacuum and supplies pressure. I pull a vacuum test first. I block off the fuel lines going to the fuel baffle about 6 inches from the baffle. I switch the fuel selector. Next I perform a pressure test 10psi and I put soap bubbles on the water separator. Lots of time the water separator isn't tight on the o-ring. You might also want to test your fuel pump on the carb. Good Luck.


Thanks for all help I am going to to those tests.
I used new mikuni needles with new seats and the old springs and spring seats.
I let you know the result.


I did a pressure test on the fuel pump and the hoses including the water Separator.
The pressure stayed at 10 psi or more. There is no leak.
Are there any other suggestions? It is 100% something with the fuel flow.