750sx problems

[RaisinBread]

Hi, my brother has a 93 750sx that hasn't seemed to ever run right. The ski is all stock with a coffman pipe that eliminates the water box. The compression is 160 on both cylinders and it has spark. The ski feels real down on power and is a slower than a stock square nose superjet. Any help would be much appreciated. If theres anything else i need to specify on just let me know and ill do my best to be more informative.

Thanks,
Hoang

 

[Waternut]

I don't know if you've figured this out yet but you may want to start looking at the impeller. The pitch may have gotten warped over time and now it's no longer any good. If the ski runs smoothly and you don't suspect engine or carb issues this may be a good starting point.

 

[aranka]

you have have bad leads from your coil causing weak or no spark. pull the boots and check the wires. if they look shiotty cut them back in 1/4 inch sections till they look good. if you do that and you still have low power you may want to replace the coil itself. its time to do that anyway given the year of your ski.

 

[SN760]

First place I would start is - get a flashlight and look up the end of the pump at the prop, checking to see if it is beat up. The edges of the prop need to be smooth-no nicks, dents, chunks missing, etc. This will kill the performance of the ski.

Pull the plugs and MAKE SURE THE GAP IS NO MORE THAN .022 Replace the plugs if needed - checking the gap before you install the new ones.

Having the gap to wide is a common mistake that is made. It can cause the motor to run poorly at mid to high rpm.