[MrJohn321]

I have a '91 superjet (650cc) with no engine mods. I seems like over the past summer, the ski had lost a significant amount of power. It runs great. No idle or starting problems, but just has very low power output throughout the powerband. I checked the compression last night and it came up with 120psi for one cylinder and 125psi for the other. I'm not sure what the compression is supposed to be. What could be wrong?

 

[fleshbazbo]

Try new spark plugs, one may be partially fowled. If that doesn't work inspect your impellor for damage on the leading (intake ) edge for rock damage, possibly from beaching your machine and not rocking or flushing rocks and sand out of your intake before taking off.

 

[MrJohn321]

Impeller is a brand new SS solas impeller. It's perfect. The plugs are brand new. Any other ideas?

 

[fleshbazbo]

Some times condensation will get in the carb and cause corrosion on the needle underneath the teeter totter. This can also cause bogging and power loss. Try a quick carb disassemble and clean. If your careful, you wont have to replace any gaskets or diaphragms. I had this problem yearly on my x-2, cleaned the needle and never had to by a gasket.Now back to my original statement, if this doesn't work try two new plugs. Sometimes you get a bad plug right out of the box or they just wet fowl first time they start up. One summer at a dealership where I worked we fixed over 20 machines right in the parking lot just by changing the plugs.Spark plug caps unscrew off the end of the wire if they read anything other than 5000 ohms replace them. If your spark plugs are not solid cap make sure the tops are screwed on tight. If that doesn't do it, next , try tweeking your L and H your screw. Start with the low speed screw, gently screw it in counting the turns(that way you can always put it back the way it was)then turn it in or out 1/8 turn from the original setting and ride the ski. It may take several short rides to see if it performs better or worse.If after several tries you don't notice a change put it back to it's original setting. Try the same thing with the H screw. If no change put it back to it's original setting. At this point if you have good compression and it still does not run, you probably have cdi box issue. My best guess is corrosion on the needle of a dirty carb with any luck you will have your ski running great in half an hour at no cost to you. good luck

 

[fleshbazbo]

One more thought, condensation or water in the electronic box can short out a boat or cut it's power way down. Open the box up (probably only 4 bolts ) if there is moisture, leave it open in your garage over night to dry out. Then smear some grease on the oring and close it up.

 

[JM-Team]

check to see what the psi should be for them that maybe is your main conflict