2005 Kawasaki 900 STX wont go over 25 MPH or 4200 rpm

[danb7684]

My 2005 Kawasaki 900 STX jet ski had it's carbs rebuilt professionally and the jet ski ran fine and hit high rpms out of water but you had to feather the throttle to keep it going.

When I dropped it in the water and ran it it would not run for more than a second or two unless i pumped the primer and it was smoking a lot. I realized I had some old gas in the tank. I flushed the old gas out and bled the lines.

Filled it with fresh gas and dropped it in and started right up. Idled decent but would die out after 10 seconds or so. When i give it throttle it bogged down a little but if i feathered it i could get up to planing speed, but only went 10 mph.

I looked at the plugs and 2 of them were fouled and one was clean?? kind weird. I went and got new plugs today and dropped it in. Now i get up to 25mph and 4200 rpm.

What do i try next?? Carb adjustment? fuel supply issue? vent issue?

 

[SpitAndDirt]

Re: 2005 Kawasaki 900 STX wont go over 25 MPH or 4200 rpm

How many hours on this ski? I just rebuilt a motor for this exact model and year. The motor is very solid and well built, however, it's still a two stroke and it is still susceptible to air leaks and clogged carburetors. Have you done a compression check yet? That should be number one! All three cylinders should be pumping about 130 psi each. If any one of the three is more than 15psi off, I'd say you have a problem. Incidentally, the one I rebuilt started out life as a rental ski and was beat to death. The aft most piston had a hole in the top of it! The ski had 442 hours on it.

 

[danb7684]

Re: 2005 Kawasaki 900 STX wont go over 25 MPH or 4200 rpm

The ski has only 52 hrs on it. I had the compression checked last year when I was first trying to deal with this issue and it was fine according to the local Kawasaki repair shop (reputable location).

Could my problem be that my carbs got gunked up again because I kept trying to run it with the old gas? It would just surprise me that they could get messed up again in just 2 weeks.

Or maybe the carbs were not adjusted after they were cleaned?

 

[SpitAndDirt]

Re: 2005 Kawasaki 900 STX wont go over 25 MPH or 4200 rpm

The ski has only 52 hrs on it. I had the compression checked last year when I was first trying to deal with this issue and it was fine according to the local Kawasaki repair shop (reputable location).

Could my problem be that my carbs got gunked up again because I kept trying to run it with the old gas? It would just surprise me that they could get messed up again in just 2 weeks.

Or maybe the carbs were not adjusted after they were cleaned?

That could be your problem exactly. Depending on what your definition of "old gas" is, you could have introduced contaminants back into the carburetors. Remember, as we depend on using fuel that has higher concentrations of ethanol, the shorter the useful life of the fuel will be if it remains untreated without a fuel stabilizer.

Try this trick: Remove the air cleaner top so you can see directly down the carburetor throats. Then start the ski on the hose and have a can of GUMOUT or other carburetor cleaner on hand. As the ski is running, spray a PUFF (less than a full second) of carb spray into the suspected dead cylinder. You can continue to intermittantely spray a puff of carb cleaner until you are sure the problem is not fuel related. If the RPM of the motor changes for the better, you have isolated the problem. From that point, you can troubleshoot fuel system issues from there.

In the rare instance you have an electrical issue, you could try swapping ignition coils. A common practice in the Sea-Doo community is to remove(read:unscrew) the spark plug caps from the wires and cut 1/2" away and reinstall the spark plug caps. The caps themselves make up part of the ignition system. You could have a good coil and a bad spark plug cap. Just something to check into. The spark plugs caps themselves usually carry a resistance of 5,000 Ohms +/- 250 Ohms.

But from my experience, especially with a ski with so few hours, I think you're really dealing with fuel issues. Let me know.