LA Compression

Two-cylinder guy · Nov 7, 2018

A compression test on my LA showed 65 psi on one cylinder and 12 on the other. I took the head off and had a guy lap and adjust the valves. The compression test is now showing 65/42. I don't know the condition of the rings and am pretty sure this engine hasn't run in at least 20 years.

Questions: Will this engine run with an 18 psi difference between the cylinders? Short of rebuilding the engine, is there anything I can do to improve the compression, ie: Squirt or spray something in the spark plug hole to help seal things up?

Two-cylinder guy · Nov 7, 2018

I meant to say there's a 23 psi difference between the cylinders.

jdal · Nov 7, 2018

It will probably run although it will have limited power. I've had mine run on one cylinder and still have power enough to load onto trailer and get it home. Chances are that rings are stuck on the piston. I've had some luck with Marvel Mystery Oil mixed in gas once they are running.

Mike M · Nov 7, 2018

Wonder if it still has a valve issue and if they should of been reground ? I had one once that had a really bad valve seat. Took lots of grinding but it straightened it out and it ran good after that. No way you could of got it good enough without a grinder. Really needed a seat insert installed but that required a complete tear down and a trip to a machine shop.

Loren in Iowa · Nov 7, 2018

After sitting 20 years, I'll go along with the guy that says some rings might be stuck. Might even have some rust on the cylinder walls.

old · Nov 7, 2018

I would fill the cylinders with ATF and if it has aa vertical exhaust pour as much ATF down it till you have a leak. Then I would let it sit a week or so. Be sure to put the plugs back in. Then after sitting pull the plugs and spin it over. Good chance the compression will come up a good bit.

LA Compression

Two-cylinder guy

Member

Two-cylinder guy

Member

jdal

Member

Mike M

Well-known Member

Loren in Iowa

Member

old

Well-known Member

Similar threads