Compression test results

Thu Jun 10, 2004 9:03 am

I'm still having problems with my cub lugging down and dying when trying to mow. I have been through the carb, governor, all electronics. It runs good (with a little choke) until you load it up.

I did a comprission test and here are the results:

cylinder 1 - 47 2 - 38 3 - 37 4 - 48

I need some comparable numbers from a good running cub or someone who knows what the compression should be. 40-50 pounds seems low to me?????

Bobby W.
Shreveport La

Thu Jun 10, 2004 9:17 am

in my opinion, 85 to 100 on a cub that has been around for awhile is acceptable, 125 for a recently rebuilt one.

Thu Jun 10, 2004 9:42 am

Wow`wee, With those numbers

[I did a comprission test and here are the results:
cylinder 1=47 2=38 3=37 4=48]

I would say your Cubs engine has worn evenly but is Plum Tuckered-Out.

Compression test results

Thu Jun 10, 2004 9:54 am

The engine has very little wear, but was seized when I got it. I probably have valves not seating or stuck rings. I think I will order some new rings and lap the valves in ...........any other suggestions???

BobbY W.

Thu Jun 10, 2004 9:57 am

Is that a wet or dry test?

Compression test results

Thu Jun 10, 2004 10:03 am

Dry, just a regular compression tester held in the spark plug hole and spin the engine over. My battery was a little low at the time so I plan to repeat the test again today after work.

BobbY W

Thu Jun 10, 2004 10:20 am


Although the readings are comparatively low, I sometimes think the test is one of the test equipment and technique as well as the engine. If the engine truly has little wear, it may be a good candidate for an experiment...

I've often wondered what would be the result of a careful dis-assembly and cleaning to free up the rings and put it back together? It seems your existing rings could be already broken in and fit better than new ones would.

I recently tore one down that had ALL the rings stuck, but was able to free them up and cleaned them. If the end gaps had not been excessive, I would have put it back together to try it myself.

It would only cost a gasket set and some time to try it.