Compression test

[garretts]

Originally Posted by twowheels

A smart ass might say when they need it but you're likely at the outer limits at 120 hours. A piston rep once told me the issue is not so much the rings (you can always slap a new set of those in) but the piston skirt gradually collapsing.

The GG250s run about 185psi iirc, but the 300s will fool you with a super low reading because of the compression bleed hole (I recording 135psi on a new 300 and just about died before I knew this).

Some would say leak-down is a better measure of health, but at 7000 rpm, how much time is there for leakdown anyway? Besides that you miss the dynamic sealing action of the rings ... best to take compression numbers periodically and change the top-end gear when they start to slip.

what year 300's have the compression bleed hole?

[Tripp]

I did a compression test on my 2012 250. I did three sets of around 10 kicks. All 3 tests landed around 125psi 😳. I've put 15 hours on the bike since I bought it. Going to get top end serviced. Does anyone recommend a kit? Or do I need to shop for all the parts separately? Have a local shop do it and look over everything.

[Zman]

That sounds pretty low. Can you measure your squish before you pull it all apart.

[(F5)]

Originally Posted by (F5)

compression tests are bull on a 2 stroke

Just pull the lid if the bike is new to you & clean the PV etc, measure free end ring gap while you are there, done in an evening & 2 beers. (Just read the instructions on melting the nylock nut on the PV arm, its all in the help bits on this forum).

Order parts if required & slap it back together, 4 beers (gotta stand round afterwards & congratulate yourself, but go upstairs before you have any more and decide its a good idea to test ride it).

Throw tester away.