Gary B.

~SPONSOR~
Apr 17, 2000
684
0
I'm stumped. My son's '97 CR80 has only 60psi of compression even after a rebuild & break-in. There is no spec in the manual, but I'm convinced this is too low. It's all stock except for Boyesen reeds. Piston, ring, & gaskets are all Honda, and the cylinder looks good. Porting is also stock. Putting a little engine oil in the cylinder when testing doesn't raise the readings, either. tried the gauge on several different motors and there is nothing wrong with the gauge. This thing's been running rich since we got it a year ago even with a #122 main and the stock needle with the clip in the top groove. I think it's running rich due to the low compression. The only fix I can think of at this point is to machine the head to raise the compression back up but I don't want to do that until I'm sure all other possibilities are exhausted.:think
 

Pete Payne

MX-Tech Suspension Agent
Nov 3, 2000
933
38
Gary B.,
Did you check the piston to ring clearance? It should be around .002"
If it is larger than that( by a fairly large amount) it might be the reason for the low compression. Also make sure you do a compression check with the throttle wide open and kick until the gauge tops out, usually in aroung six kicks. Also if this is a threaded in gauge make sure it has the long adapter (will look the same length as the spark plug) and it should also have a schrader valve in the end of it that goes into the cylinder. Hope this helps!!!
Pete.
 

Gary B.

~SPONSOR~
Apr 17, 2000
684
0
Pete - do you mean the ring end gap? I don't remember the exact measurement, but it was in specs. And yes, I do have the threaded in type of gauge.
 
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