Cylinder Pressure

[vccthrasher]

Hello. I have a 1982 Kawasaki JS550. I just check the cylinder pressure and I have 120psi in each cylinder. I know with my Seadoos, a minimum cylinder pressure of 130psi i recomended. Is this the case across the board with jet ski engines?

The 550 have a very weak takeoff and smokes a LOT when the engine is under a load. I know the smoke could be caused by carb setting, but the power issue could be from the lack of cylinder presure. Is this correct?

Also, the carb on the 550 has 4 avalible adjustments. One is the idle screw and one is in the right place for the high speed. One would be a low speed, but what is the 4th one for?

Thanks for the help.

 

[93mustang97sea]

If both cylinders are within 10% of each other your fine. Until you get below like 120 I feel. Thats how I go about it.

 

[vccthrasher]

Okay. Thanks for the help. I now need to adjust the carbs and see if I can get it to stop smoking so bad.

 

[Dr Honda]

If it's a stock 550... that's about right. It was only a 40 hp engine. It's been a few years... but 125/130 was all you would see on a rebuild.

Smoke can be the carbs being out of adjustment... or way too much oil in the mix.

The extra mix screw was a mid adjustment. It was really not needed... that's why you don't see it anymore on the new carbs. Look up the settings for the screws, and after that... don't touch the mid screw.

 

[vccthrasher]

Thanks Doc. I had no idea it was only a 40hp engine. I guess the power it has is what it is supposed to have. I will continue to adjust the carb and see what works. Would you happen to have a guide to jet ski carb tuning? I know how to tune rc engines but that is it. I know they are similar, but a guide would help.

Thanks

 

[Dr Honda]

It's kind of the same thing. Set the idle speed... set the idle mix for a good smooth idle, and a responsive mid. and set the high for peak RPM.

There is no good way to tel you how to adjust the mid screw.

Now... unlike R/C engines... if you go too lean on the top... you will kill the engine, and you can't hold a screwdriver on the carb while riding in the water. So, you will have to go for a ride, and do a plug chop, and read the plugs to make fine adjustments.

I have a service manual for the old JS series... but I will have to find it. If you are going to work on it... you are best to go buy a manual. It will have the needle settings listed.

 

[vccthrasher]

I'll do that today. Thanks again for all of the help.