Is there a tool to check compression on a motor.
I have an OS .91 and It feels like it has low compression, but I am just not sure.

I use the Armstrong gauge for measuring compression.

It is a relative measure compared to other engines or the same engine in the past

If it is a ringed engine, it can feel like it has low compression, in case your engine are a 4 stroke engine keep the trottle barrel open then compression feel better when you are testing compression.

But important of all: are the engine running well in idling and no trouble in trottling = compression are ok.

I never had a compression tester to measure compression in my engines.

Edit: missing text..