Other OEM 760 motor with 210 compression in one cylinder?

[McDog]

Trying to help a neighbor get his two waveraiders going that have been sitting for almost two years. I know I need to replace fuel, fuel lines, and clean out the carbs. I did a compression check and one ski had 170 on the front cylinder and 210 on the rear. I'm shocked. I can't figure out what would cause this unless something has built a nest in the motor or something weird like that.


Any ideas?

 

[Waternut]

That's almost exactly what my big bore compression numbers were. Cylinder and rings were beyond max limits so the piston to wall clearance was too big.

 

[CARBONX2]

1 cylinder rebored?

 

[easyrhino]

5 pounds of carbon. 3 lbs on the front pistion, 2 on the back. Have to question the guage.

 

[McDog]

No doubt a cheap guage but results were consistant. Ski is as stock as can be but has been sitting forever.

 

[Waternut]

Just out of curiosity... Did your neighbor winterize it last winter and never ride it this summer? Excess oil can really throw the compression numbers off. If you haven't, maybe run it and rev it up a little and check the compression again.

 

[Matt_E]

That's almost exactly what my big bore compression numbers were. Cylinder and rings were beyond max limits so the piston to wall clearance was too big.

If the clearances between piston and cylinder are too big, you'll get abnormally low compression numbers.

 

[McDog]

Can't get it to start. Other ski started up but ran like crap. Guess I can clean out the carbs and replace fuel lines and put fresh gas in it and then see how it goes after that.

 

[ryan]

waternut has got it . its loaded with oil.