1996 seadoo GSX Wont rev Above 4k RPM

[TCircuitry]

Hello everyone, my brother has a 1996 seadoo gsx, we rebuilt the engine and got it running, it has 150 PSI on both cylinders, I cleaned the carbs and rebuilt them properly and we had it running before, but now it wont rev above 4k rpm, we checked and replaced the regulator, have all new fuel lines, fixed a fuel tank venting problem that prevented the fuel from the carbs from going back to the tank, and now we are cleaning the RAVE valves which we had put in properly. We are now attempting to clean the rave valves to see if that does anything. This is so frustrating! and the RAVE Valves didnt look too terribly dirty. It starts everytime reliably and idles well but wont go above 4k rpm and we are tired of trying to diagnose this problem. Please Help!

 

[GGuillot]

Hello everyone, my brother has a 1996 seadoo gsx, we rebuilt the engine and got it running, it has 150 PSI on both cylinders, I cleaned the carbs and rebuilt them properly and we had it running before, but now it wont rev above 4k rpm, we checked and replaced the regulator, have all new fuel lines, fixed a fuel tank venting problem that prevented the fuel from the carbs from going back to the tank, and now we are cleaning the RAVE valves which we had put in properly. We are now attempting to clean the rave valves to see if that does anything. This is so frustrating! and the RAVE Valves didnt look too terribly dirty. It starts everytime reliably and idles well but wont go above 4k rpm and we are tired of trying to diagnose this problem. Please Help!

I have a 96' GSX, the only areas I can think of that would be causing your issue is either fuel delivery or something electrical. Did you rebuild the carbs with genuine oem kits? what was the needle/seat pop off? Are the spark plugs properly gapped? What voltage are you getting at idle at the battery? On each end of the spark plug wires cut back 1/4" to improve spark connectivity. Run it with the red wire on the rectifier disconnected for a brief moment and see if anything changes. Run a fuel selector and strainer (under steering) bypass and see if it changes..

You're on your way to narrowing it down, carbs must be perfect, and it is possible to get a brand new rectifier that's bad, so verify voltage at the battery and do the red wire connected/disconnected to rule it out.

 

[TCircuitry]

I agree we are incredibly close to figuring this out, like I said It starts up and runs fine at idle and reasonable throttle response but wont go above 4k RPM.
Things I have tried Ima just make a list:

Cleaned RAVE Valves and they are put in correctly and move smoothly

Checked carbs with no obvious issues

Carb popoff is 30 PSI consistently on Both Carbs

Spark Plugs are gapped correctly (Brand New Plugs as well)

Compression is 143/145 PSI (Pretty Decent)

Unplugged the rectifier wire and still no change in RPM

Had a venting problem with the fuel tank as it is now summer but fixed that, caused the tank to stay pressurized and shoot fuel out of the return lines when i unhooked them

Carbs I had rebuilt to factory spec with Genuine OEM Mikuni Carb kits (Believe me I tried aftermarket before and you just get air leaks on the pop off pressure test, thus causing fuel pressure problems).

High speed screws and low speed screws were set to factory spec and even played around with

Battery voltage reads 13.3 voltsish and can go higher since it is a brand newly charged battery

We have replaced literally about everything in this boat


Next two things I will be trying are double checking my timing on the rotary valve to make sure its correct when we put the engine back together since I currently have the carbs off anyways, and checking the jet pump to make sure it has oil in it and isnt dry (happened to my 96' spx my front main seal in my pump went out and leaked all of the oil out and ran horrible plus seized up the bearings and wouldnt go past 3,500 to 4k rpm)

Im just narrowing down anything at this point, I do question if it has good spark between both cylinders (like it would be missing on a cylinder but idk)

 

[TCircuitry]

Found out that the rotary valve I installed was 15-20 out of spec, put it into the correct position, am taking the boat down to the river to see what it will do now.

 

[TCircuitry]

Still having the same problem even though it runs slightly better. It sounds like its missing on a cylinder. We are so close to figuring this out!

 

[GGuillot]

Still having the same problem even though it runs slightly better. It sounds like its missing on a cylinder. We are so close to figuring this out!

Did you clip the spark plug wires back 1/4" on each end like I mentioned above in post #2?

 

[TCircuitry]

Going to try that next, we replaced the ignition coil 2 years ago

 

[Da.Doctor]

Your problem must be misfiring in one of cylinders try to start it with one spark plug each time to see which one is notcworking

 

[etemplet]

Carburetor Pop-Off setting too low. Are the 3 holes in the carb barrel clear and spraying strongly when you dod the test. If you don't know at this is check out the carb thread. I've found the 787 likes 36-38 pounds of Pop-Off on my skis. I've tried settings from 23 psi on up. 33 psi wasn't bad. They higher I went the better the engine transitioned. My wife's ski would not accelerate above 37mph unless the impeller got some air. When I got the good flow from the three holes in the barrel and the pop-off on spec using the proper spring... her ski is awesome. Give that a try and good luck with it !!

 

[TCircuitry]

realized that he used aftermarket needles and seats which were leaking, replacing them with genuine and see what happens.

 

[etemplet]

Good Luck !!

 

[TCircuitry]

Determined what the problem was!! The Low Voltage Signals in the electrical box that come from the CDI and plug into the ignition coil were loose and corroded. I wire brushed and squeezed the lugs to make them tight and then his boat stopping missing on a cylinder!! He said it was more power than he ever felt before!!