how much compression is needed?

[jawalth6]

How much compression does your average three wheeler need to run? Some people say at least 100 psi but one of my atc 90 had 70 and ran good.

[barnett468]

How much compression does your average three wheeler need to run? Some people say at least 100 psi but one of my atc 90 had 70 and ran good.


Hello


How much compression does your average three wheeler need to run? Some people say at least 100 psi


Why do you want to know?

It’s around 105 psi

xxxxx

one of my atc 90 had 70 and ran good.


Absolutely impossible the math/physics simply does not allow it therefore either your gauge was inaccurate, incorrect for the test [needs to have a short small id hose] and/or improperly done. This would calculate to a static compression ratio of approximately 5.0 using an intake valve closing time of 50 degrees abdc.

xxxxx

Hope this info helps

[barnett468]

Hello

It could run on less depending but it won't run even close to "good" as you claim.

[dougspcs]

The factory spec is different for each machine..the 200cc Honda is 156+-14psi, the 110cc is 177+-psi.

Those who suggest that significantly lower numbers are fine are only fooling themselves or wanting to avoid the repair.

True an engine will run at a considerably lower compression but run well is another story. If the numbers are even 30-40psi below spec a whole list of issues can result from smoking, to difficulty starting or getting a regular idle. Also a very sharp decline in power..

One old school method to gauge how much compression is lost due to ring wear is simple. Use your compression gauge and get your engine compression, then shoot a small amount of oil into the cylinder and slowly turn the engine over a few times. Then repeat the compression test..a sudden jump on the second test, say 20-30 pounds is a definitely a problem.

An ATC90 running on 70PSI..I say is impossible! I'd sure want to see the numbers on a properly calibrated compression gauge to believe that! Until then I say it's fiction...

[jawalth6]

My gauge must be ruined. It was a 20 dollar Harbor freight one.