Cub engine compression

With the throttle and choke wide open, charged battery for good rotation, and spark plugs out, 125 or more for a gasoline only, 20% less for distillate. If 2CC (teaspoon) of oil in each cylinder raises the compression 15 pounds/sq in, it probably needs rings. All readings require at least 5 solid compression strokes to get to max. Check the accuracy of the compression gauge as well. Jim
 
because of errors that can be made its not how high the readings can be but the important reading is are all cycls close to each other you don't want a very weak one. Just watch the meter when turning engine over see how much is gained between first and second rpm and so forth. That is a small engine so don't expect great high readings it is a low compression engine even when new.
 
factory manual says with flat top pistons 120 lbs. and that's all I ever ended up with on the dozen or two I've rebuilt.
 
Forgot to mention this before. Don't be too quick to blame a valve if it appears stuck.I have had several that appeared that way with all the normal checks. It turned out to be a STUCK lifter. They are splash lubricated and once in awhile when a motor sits awhile and a lifter is holding a valve open it may get some rust on the upper part of it and not go down like it should. Before I remove a head any more I pull the side cover behind the manifold and make sure that isn't the problem. I spray the lifters with PB blaster and make sure that both lifters on the bad cylinder are moving all the way up and down and not sticking. These motors don't have much spring pressure so it doesn't take much to make em stick. It's easier than pulling the head and finding out later. You'd have to pull that cover anyhow if you have to remove the valves. Good luck!
 

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