08-17-2012, 09:43 PM #1
New Piston and Rings, Low Compression
I recently had a piston go out on my 1994 Polaris 750 SLT. This is my first piston replacement on a ski. I replaced the piston with a new standard bore piston, and I replaced the cylinder with a lightly used cylinder that had been miked and honed by a professional PWC mechanic. I made sure to align the rings per the manufactures instructions. All of the gasket surfaces were cleaned , and new gaskets installed. After I torqued the head and cylinder down, I ran a compression test to see what I was getting. I am only showing 35 psi. I know that I need to seat the rings, but I am concerned that the compression is too low, and that I may be missing something.
Any help would be appreciated.
08-18-2012, 07:00 PM #2
- Join Date
- Oct 2006
- Cleveland OH
What are your ring gaps?
What's your piston to cyl wall clearance?
Welcome to the Hulk BTW.
08-18-2012, 08:01 PM #3
08-18-2012, 08:41 PM #4
Welcome to the Hulk! Definitely check your ring gap clearances. There have been issues with rings being sent out with improper gaps lately.
08-18-2012, 08:57 PM #5
Glad to be here! Thank you for the help. I will check the gap and clearance in the next few days. Didn't think to check it (Rookie Mistake). It was also suggested to me that I may just need to run it a little bit so the heat can expand the rings. Is that a good idea, or is my compression reading way too low for that to work?
Thank you again.
08-18-2012, 09:01 PM #6
Way too low. Don't really think it will even run that low. check you gaps by installing the rings only (no piston) in the cylinder, then push the ring down a little with the top of the piston upside down in the top of the cylinder. Use a feeler gauge to check the gap.
08-18-2012, 09:09 PM #7
08-18-2012, 09:17 PM #8
.008 - .018. You can try reusing, most will use Permatex copper gasket spray on the head gasket when reusing to ensure a good seal.
08-19-2012, 12:29 PM #9
Found the problem. When I pulled the rings, I found that I had broken the bottom one. I should have realized it was taking too much force to get the cylinder on.
I noticed a couple of you are from the Cleveland area. Do you know any places that stock these rings localy?
Thank you again
08-19-2012, 02:33 PM #10
Not that I know of. Probably going to have to order them.
Where do you usually ride??
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