GSX won’t go full throttle

[CydneyH]

I have a 1996 GSX. It will start up and rev up good not in the water but soon as you put it in the water it doesn’t wanna get up and go. Maybe only go 1/4 throttle. The wear ring looks fine. My compressor is only 125 & 115 which I know it should be around 150. Could that cause the GSX to not wanna get up and go? Or does it sound more like a fuel issue?

 

[mikidymac]

I would lean to fuel issues as a stock carbed 951 should be about 130psi compression not 150 so you are not that far off. The 10 psi difference in cylinders is not ideal as they should be very close or the same.

 

[CydneyH]

It’s not the 951. It’s the 787. Not sure if that makes a difference or not.

 

[mikidymac]

Sorry, thought you said 99 GSX.

Yes, the 787 should be 150 so if your compression numbers are correct then that is your issue. Something is wrong inside the engine at those numbers.

 

[CydneyH]

Sorry, thought you said 99 GSX.

Yes, the 787 should be 150 so if your compression numbers are correct then that is your issue. Something is wrong inside the engine at those numbers.

Your fine. I do have another ski that has that motor and has a leaking problem from the back but can’t find where it’s coming from back there. But yes how do you suggest doing the compression test. I read different ways but wanna make sure I do it the correct way so I can get the most accurate reading.

 

[Saludadoo]

Look at your voltage, because the more the motor spins faster the magneto makes more voltage and if the voltage regulator is bad it sends to much voltage to the CDI/Mpem
Easiest is to hook up a volt meter to the battery and go ride it and see if the voltage goes above 14volts

 

[CydneyH]

Look at your voltage, because the more the motor spins faster the magneto makes more voltage and if the voltage regulator is bad it sends to much voltage to the CDI/Mpem

Easiest is to hook up a volt meter to the battery and go ride it and see if the voltage goes above 14volt

 

[CydneyH]

When you put it in the water than it’ll barley go maybe 1/4 throttle. But if you have it on trailer it sounds as if it’s rev up just fine

 

[mikidymac]

They all run fine out of the water, LOL.

To test the voltage regulator, just touch the probes of a volt meter to the battery terminals. You can get one for under $10 at Harbor Freight.
With the ski off you should have at least 12V when cranking the engine over it shouldn't drop below 12V once it is running and you rev the engine up pretty high it shouldn't really go over 14V.

To test compression pull the spark plug and ground the plug wire on the provided metal suds.
Good, charged, strong battery.
Fuel OFF.
Install the tested.
Hold the throttle wide open.
Crank the engine over until the needle on the gauge stops climbing.
Repeat for other cylinder.