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Discussion Starter #1
Just read XCRMAN's posts for new rings and I have a few questions.

I have a 90 triple 650 with approx 90 lbs compression in all three cylinders.

I purchased the sled second hand and the owner mentioned he had redone the rings & pistons.

I just want to change the rings for higher compression, is there a specific size of ring or are they standard for the year/model.

Will this help my compression?

Thanks.
 

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You have to know what size piston is in there first, then buy the appropriate ring set. How did you check compression. Warm engine or cold. Throttle must be held wide open. remove all spark plugs and pull till the guage wont rise any further. try this if you didnt do it this way and see if the numbers go up.
 

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It will only help if the rings are bad or not seated properly. If the rings are good and seated properly, then this will not "increase" compression. The 650's have a high compression head gasket that will help. You could also have the heads shaved down.
 

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hmm, ive never heard/seen anything on rings that would "boost performance" i could be wrong though. i know of chrome-molly rings in cars that last longer than conventional rings, but i am unsure of this application for snowmobiles. if your looking for compression gains i would do like it was mentioned, you can shave your heads, or get a powerdome set that comes with different spacers to change your compression psi. have you tried or thought about all the usual stuff to "hop" your sled up,,,,,,,,pipes/clutch/gearing etc.
 

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yeah that compression seems very low for a 650 hell my 600 cold without the throttle open sits at 120psi open the throttle up and boom in the 130's

bobby

My wife said its me or my sleds... Im sure gonna miss her
 

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what lbs are you trying to get out of it, how are the gaskets? sounds like the rings are not seated right or somethimg
 

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Discussion Starter #7
I didn't hold the throttle open when I cranked it over. I will try that tonight. Should the engine be hot or cold?

I replaced all the head gaskets at the beginning of the season. (Coolant Leak)

What lbs should it have been new?
 

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Do your test the same as last time so we can compare the new figures. if you did it cold do it that way again. Re-torque the bolts in the proper pattern first unless you already did this after a few hours of riding when you replaced the gaskets. you should be in the 120 to 130 range. let me know.
 
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