My 1994 kawasaki 750 ss jet ski will only go half speed when I have the throttle wide open?

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compression check , 100psi or more ! battery and connections good ?

what kind of jet ski we talking about year make model

Since this is not a computer game, you might want to repost in the correct catagory.

If the carburetor was properly cleaned including the teeter-totter float needle then you may just have accidentally changed the setting screws. Try setting the the high end and low end adjustment screws the standard settings are: Low speed screw: 3/4 turns out (+ or - 1/4 turn for fine tuning) high speed screw: 1 1/4 turns out (+ or - 1/4 turn for fine tuning) If the previous owner rebuilt the whole machine but could not figure out why the boat would not rev out, the next thing to do is remove the water box and and split the halves. http://www.bikebandit.com/houseofmotorcycles/1995-kawasaki-750-ss-jh750a4/o/m3253#sch27834 If a mouse nest has been built in the exhaust system the extra back pressure could be the problem. If the exhaust coupler has broken rubber tubes, has come apart, or has not been put together correctly that might also be the cause of the problem. http://www.bikebandit.com/houseofmotorcycles/1995-kawasaki-750-ss-jh750a4/o/m3253#sch29444

Your 750 jet ski does not have a gear box. If you are referring to what looks like a filler cap on the front of the motor, that is the generator/flywheel cover and it is a dry compartment and should remain that way.

Check your plug color. You may be having a high speed mixture problem. Is your ski spitting water out the tiny hole on the side? You should try flushing the engine, you could have a motor full of sand if you beach the craft but do not wash the sand out of the back before starting. Also inspect the engine water tubes for cracks. From the hull to the motor and from the hull to the jet pump.

You are deal with moisture corrosion in your carburetor. Take the carb off and clean it paying attention to the corrosion on the rubber tipped needle. Also open your electronics box and make sure that it is dry.

Stock needle settings are: LOW 3/4 +/- 1/4 . HIGH 1 1/4 +/- 1/4

yes but its not easy you pretty much have to take all the exturnal parts off carbs, exhuast airbox if u have one but it can be done make sure you have a swivle for your socketsbest place to get a starter is sbt.com short block tech