What is "good" compresion?

[dirtface]

I have a 1986 200x here, It won't run, checked it and it shows 30psi on the tester. I then went in out of curiousity and checked my perfectly running 1984 Big Red, and it showed around 50psi. Now, I have read on here that you have to have at least 100psi for a bike to run. I honestly don't think any of the thirteen running bikes that I own have over 100psi. Can someone please give me a educated answer to what psi a bike needs to run? Is my compression tester junk?

[RedRider_AK]

Maybe your big red has some REALLY REALLY worn rings.

[84honda200s]

ok 156 psi is max it should have with stock piston and rings. if there is more than a 10% difference then it wont run worth jack. so basically what this pos book is telling me is if you are running lower than 140 than you need to do some work.

[erectordale]

there s a large differance in compression from 4 stroke to 2 stroke 2 strokes require lot's more than a 4 stroke

[dirtface]

OK, would someone please go out to there garage with a good compression testor and check a 200, big red, or a 4-stroke of some kind and tell me what it reads? If a 4-stroke is less than a 2-stroke, what is "normal" for an old running 4-stroke?

[84honda200s]

there s a large differance in compression from 4 stroke to 2 stroke 2 strokes require lot's more than a 4 stroke



but dale thats what the book is telling be for 4 strokes. plus mine has 10.25:1 and reads well over 156. but maybe thats why i keep blowing recoil ropes too lol. when i get my engine back together i will do a test. no better yet i will do a test on my fathers dx (its a 225) tomorrow.

[tapper190]

Make sure when you do the test, you hold the throttle wide open.
Tapper

[troy]

heres the test on my 200es, 90 psi with closed throttle and 120psi at WOT AFTER putting a drop of oil in the cylinder ..probley a good reason why she will not start. and when i did get her to start it put out blackish smoke, can you say ring job?...LOL

[84honda200s]

yea ring job for sure and probably valves too.

[Erics350x]

heres the test on my 200es, 90 psi with closed throttle and 120psi at WOT AFTER putting a drop of oil in the cylinder ..probley a good reason why she will not start. and when i did get her to start it put out blackish smoke, can you say ring job?...LOL

Black smoke is a sign of flooding/running rich. 120psi should be enough.

[Rustytinhorn]

My '81 Atc200 (185) with WOT measures 120psi. However, I am 5280 feet above sea level and also my wheeler smokes quite a bit.

[4cylinders]

hey, first you need to set the valves, then read the instructions for the compression tester. crank the engine until the guage stops going up. now what do you have?