Evaluating 861 engine, compression test

Beanmedic

Member
Evaluating an 861 and an 860 for which one to keep, which one to sell. Both have 172 ci gasoline engine. This is the 861:

Tractor had not been run in a year or so when I bought it. I did have to repair a short in the distributor to start it...and while in there replaced points/condenser/rotor/cap. Also replaced the carbon string plug and coil wires with real wire core. New IC14 coil and rewired around resistor.

The 861 needs a carb rebuild, which is scheduled. Plugs are dry sooty. Cranks and runs with just over 20 lbs oil pressure (confirmed with two gauges).

Compression dry/wet readings after warm up, throttle open:

165/175 145/160 160/165 155/175

I'm not sure what the readings are supposed to be...are these high? I'm sure the differences between cylinders and between dry/wet are more revealing.

Specs in Shop Manual say compression 205 lbs at 1200 RPM. But, that doesn't tell me what it should be for a compression test. Advise?

One thought I had is, after the carb rebuild to just work it good and see what changes, if anything???
 
Those numbers aren't bad, that's about what my 861 has per
cylinder. Remember it's an old tractor and if the engine hasent
been rebuilt, the ware parts are going to ware. Mine still has
plenty of power with those compression numbers, though it
does carry 40-45lbs of oil pressure all the time. You might
have a main bearing or pump issue there.
 
Thanks. I feel better :)

Pulled the carb for soaking and rebuild and put a shot of ATF in each sparky hole while I wait on carb to come back together. Then going to redo compression tests and run it to see what happens.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top