What could be the cause of extremely high compression? 250 psi

[darrylgood]

Hello all.

I have a 97 xp that I am going to be rebuilding the top end. New pistons, cylinders bored. I am doing this because one cylinder is reading 30psi because of detonation.

My question is in regards to what used to be the good (front) cylinder (no detonation). I just re-tested the compression and it is now 250 psi!

What could cause such a high compression?

Thanks so much

 

[BMANN06]

Hello all.

I have a 97 xp that I am going to be rebuilding the top end. New pistons, cylinders bored. I am doing this because one cylinder is reading 30psi because of detonation.

My question is in regards to what used to be the good (front) cylinder (no detonation). I just re-tested the compression and it is now 250 psi!

What could cause such a high compression?

Thanks so much

My Guess would be that you have water/coolant/liquid in the cylinder or your gauge is faulty.

B

 

[darrylgood]

The only thing that I have done is spray fogger in the cylenders for winter storage. Could this cause the increased compression?

I didn't know that water in the cylenders would increase the compression.

 

[darrylgood]

Also the tester has been tested it works fine

 

[BMANN06]

The only thing that I have done is spray fogger in the cylenders for winter storage. Could this cause the increased compression?

I didn't know that water in the cylenders would increase the compression.

That's likely the culprit ... have you got a quarter of a can dumped in there? Mind you you'll probably want to rebuilt both jugs at the same time so their compressions are similar. You'll prolly get some of the experts on the site to chime in that department.

b

 

[BMANN06]

I didn't know that water in the cylenders would increase the compression.

Absolutely, As the piston "goes up" nearing TDC is where the most pressure is made in the cylinder. If you have a liquid, water/fogging oil etc it takes up space(volume) in the cylinder thereby causing such high compression. I'm terrible at explaining things sometimes so i hope this helps.

 

[darrylgood]

Thanks so much, BMANN06

 

[BMANN06]

Also the tester has been tested

Thats awesome! :rofl:

Thanks so much, BMANN06

Hey no problem! If you have questions about your build be sure to post em' up here. You'll get all the info you need! Make sure you rebuild both of your cylinders though .. This will save you headache in the spring!

:cheers:

 

[darrylgood]

Thanks BMANN06, I will bedo both for sure. I did have one question about liquid in my crank case though. I posted it here: http://www.seadooforum.com/showthread.php?t=37406

Thanks