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 Compression drop

 Created by: croc7
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 Posted: Jul 21, 2014 10:43AM
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Sounds like you have done all you can, If the hiss from the dipstick or oil filler is somewhat intense I'll agree it's time to suspect the rings leaking bear in mind that you will always hear some hiss, leak past the rings they dont seal 100% when running let alone stationary! Did you do the leak down on all four individual cylinders? that way you can get a feel for the difference in loss between each cylinder and sound of the hiss, is it more intense through #1? Listen through the oil filler cap this time. and what were the % loss figures for each cylinder?

Mini's are like buses they come along in a bunch

 Posted: Jul 21, 2014 10:28AM
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US

I should have mentioned that I did a compression check before the trip to Milwaukee and all cylinders were in the 185-190 PSI range.  After the trip is when I did the second compression check and found the #1 cylinder low.  Did a valve check/adjustment, rechecked compression with the same result.  That's when we did a leakdown test-had no air loss through the carb or exhaust-at least what we could hear.  We did hear an air hiss coming from the dipstick hole.  Compression check showed the other three cylinders remained at about 185-190 PSI, so didn't see any reason to squirt oil into those cylinders.

 Posted: Jul 21, 2014 07:36AM
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Rings would be the last thing I would suspect. Valve sealing would be the first.

I'm with minimans.

 Posted: Jul 20, 2014 11:26PM
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Did you check the other three with oil? I would bet they would jump up about the same? puting oil in always raises the compression, you need to do a leak down test to find out where the compression is going, don't just assume it's the rings! have you checked the tappet clearence? could be as simple as that. do your full diagnossis first before jumping the gun with quick fix solutions................Oh and 65 up to 200 would be 35psi..........

Mini's are like buses they come along in a bunch

 Posted: Jul 20, 2014 03:05PM
 Edited:  Jul 20, 2014 03:57PM
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I've lost about 25 PSI in one cylinder, down to 165.  Squirted some oil in the bore, did another check and compression jumped to 200, so am guessing that the rings have gone south, not sealing.  It's been suggested that I try a Yamalube product called 'Ring Free', the thought being that the rings might be fouled/stuck with carbon.  It might be just more 'snake oil' but 'Ring Free' has good reputation in the motorcycle and boating community and is used to keep the combustion chambers, valves and rings free of carbon. Has anyone tried it?  Or thoughts?