Compression tester?

[The1970's]

I've got a harbor freight automotive compression tester and suspect that it is reading low on my GS750. I'm getting low 90's on all 4 cylinders. Im getting low numbers on all my other bikes too. But when I tried it with my truck it works great and reads 160+. My bike puffs some smoke every once in a while and consumes a small amount of oil but with readings in the low 90's I would suspect a lot more problems than that?

I was hoping to get a good reading just so I can monitor how it's doing and gauge when I should do the top end rebuild. Im thinking that with maybe 3 feet of rubber line to the gauge the extra volume in the line is increasing the combustion chamber volume enough to lower the reading. What do you guys think? What kind of compression tester works well on these small engines?

[fixmybrokecomputer]

Are you holding the throttle wide open during the test? Someone correct me if I'm wrong, but I believe you'll get low numbers unless you do so. HTH

[aclaytonb]

I get 90s with throttle closed, 130s with throttle open. Been there, panicked, re-read, tried again...relaxed.

[The1970's]

Yep those are with the throttle open. It seems to read right around mid 90's on every bike I have. Even a 2006 XT225 that I'm certain doesn't have low compression. I don't get it

[jsandidge]

I have the exact same numbers with my HF gauge. I don't know if some of them are good or not, but apparently we've both got lemons.

[gustovh]

I always use two gauges, one to double check the other. My HF gauge works as advertised.

V

[aclaytonb]

My HF doesnt read over 130...period. No idea. I only really trust their tools if its a situation where I expect the tool to break.