compression

[JBohannon]

Just getting ready to put my 89 Waverunner 500 for the winter. It has been running ok. Starts fine. I just ran a compression check. Both cylinders showed about 122 psi. Think I need to have a little work done on it. How far should I go. Can I expect better performance after improving compression. Thanks.

[1fastski.com]

Re: compression

if there even there ok .

[JBohannon]

Re: compression

At what point(psi) would you say I need to do some engine work.

[CTXL1200]

Re: compression

I had a 1990 WR500 and it was very reliable. With your compression I wouldnt mess with it.

You have to keep in mind, it is only 500cc, so it is only designed to do maybe 30-40 mph?

[wmsky]

Re: compression

At what point(psi) would you say I need to do some engine work.

How much confidence do you have that your compression gauge is accurate? It is very easy to get a low reading without a good gauge that has the right size adapter and one with a Schrader valve in the tip, or by improperly measuring the compression, http://www.sbtontheweb.com/forum/showthread.php?t=16019. As others have said, it's more important that both cylinders be close - within 10% of each other, as long as the compression is within the recommended range for your engine - again assuming a good gauge. I'll see if I can dig up the recommended range for your Waverunner tonight.

OK. Neither of the manuals I have specify a range. They both state that the factory compression is 142.2. .2, that's funny. :p I hadn't noticed that before. Who measures compression down to tenths? Yamaha I guess. In any case, if you get 122 in both cylinders, you're good to go.

As to how low before the engine would need a top-end job, neither of the manuals I have mentioned that, which seems kind of strange. Maybe someone else here has a good idea about that.

[WATERCRAFTSERVICES]

Re: compression

You are fine at 122 psi on both. Believe it or not that engine is a very reliable and will last a very long time if maintained. It is actually a Yamaha 25hp outboard engine turned sideways and modified for PWC application. There are still many of them on the water. That should say something.