5 replies to this topic

[steve1979]

Hi guy's, i checked the compression on my 250 txt pro and it was reading 150 psi. I thought that seemed a little low so i replaced the old piston etc with the S3 piston kit. The barrel looked visually really good, no signs of wear at all but the old piston had signs of blow by. So it's all been replaced and i would say run in "it's had about 6hrs worth of running" i also deglazed the barrel with wet and dry (carefully) although it wasn't to bad in the first place.

However now iv'e done a second test to see if the compression would be up and it's still the same. Baffeling.

Held throttle full on etc while kicking her over.
I'm thinking to ask my mate if we can check his 2009 beta evo 250 although that might upset me if his is way higher.

touch wood my bikes running great anyway but i'm interested to see what it should it should be at.

[betarick]

Hi 150psi sounds good to me on a 2stroke engine i normaly only see about 180psi on 4stroke car engines when checking compression at work on cars! Tested a diesel today and got 400psi.

[max1956bikes]

150 is good

[steve1979]

Thanks guy's, thats a good responce i was expecting someone to tell me that was way low and potentially something amiss.
Happy days then

Cheers guy's

[Anotherfive]

Do you check it once hot and how do you do it would like to test my 08 beta

Edited by Anotherfive, 13 October 2010 - 08:55 PM.

[steve1979]

I check mine when it's cold. You will need a compresion tester that either screws into the spark plug hole or the version like mine that you push down onto the plug hole (kinda difficult to do while kick starting the bike, easier with the screw in type)
Method is quite simple
1) remove spark plug and place plug cap out of the way.
2) push or screw tester into plug hole
3) hold throttle wide open
4) kick start the bike with a good hard kick approx 4 times in a row quite quickly
5) remove tester and check what psi it's reading........job done

If it's lower than it should be it's probably needing a top end rebuild (new rings etc or full piston kit).
I would imagine your 08 beta should be fine though but apparently doing alot of wet riding ie burns can wear a piston out quicker unless the filters in tip top condition.

If you are using the press on tester rather than the screw in type, having an assistant hold the bike and the throttle open is a big help.

It would be interesting to see what psi your getting. If i get a chance this weekend i'm going to test my mate's 09 beta it's not had much running, he bought it new then stepped up to a 09 290 evo so the 250 doesn't get used. The lucky sod