Rare Scottish Tree Badger Posted July 12, 2005 Report Share Posted July 12, 2005 What kind of difference would you expect to see in cylinder compression when doing the test cold as opposed to doing it on a fully warmed up bike? My example: I only managed one test before I burnt down, and that was a hot test done at about 60F (15 degrees C). I recorded 148psi. Rare. Quote Link to comment Share on other sites More sharing options...
racer Posted July 13, 2005 Report Share Posted July 13, 2005 Ive got no idea Rare maybe you can convince someone with a tester to thread it into their head after 15 minutes of riding. Quote Link to comment Share on other sites More sharing options...
Nightrider Posted July 13, 2005 Report Share Posted July 13, 2005 Your probably only looking at like 5-10 psi max.I get 155 hot and 150 cold Quote Link to comment Share on other sites More sharing options...
Rare Scottish Tree Badger Posted July 13, 2005 Author Report Share Posted July 13, 2005 Your probably only looking at like 5-10 psi max.I get 155 hot and 150 cold 392191[/snapback] That's a surprize. ... I was expecting to hear that a cold test produced a higher compression on account of the air not being heated by the hot internals . I guess the heat doesn't have time to effect the air while cranking, and the expanded piston/rings and reduced (warm) piston to bore clearance raises the compression. Hmmmmmm. Rare. Quote Link to comment Share on other sites More sharing options...
fixitrod Posted July 14, 2005 Report Share Posted July 14, 2005 The pistons and rings swell when they get hot. The reason for a cold test is to get an accurate reading with most of the oil and gas out of the cylinder and to prove proper maching, and I'm sure there are more reasons. Quote Link to comment Share on other sites More sharing options...
dbkid13 Posted July 14, 2005 Report Share Posted July 14, 2005 I had 115 when it was cold and 125ish when it was warm, pretty much stock. Quote Link to comment Share on other sites More sharing options...
Meat Posted July 16, 2005 Report Share Posted July 16, 2005 Interesting. I'll have to test mine and see what I come up with. BTW I test mine cold. Quote Link to comment Share on other sites More sharing options...
BenBB Posted July 16, 2005 Report Share Posted July 16, 2005 Hey Meat how the hell is it going buddy? I won't be testin' mine hot anytime soon heh, but I agree with Rodney that it oughta be higher when warm, I'm just not gonna burn the crap out of my forearms to prove it...but think about a tired motor that's getting low on compression; it's a bitch to start cold but when warm it fires right up because the piston/rings have expanded, so it's got a tighter seal and numerically higher compression... Quote Link to comment Share on other sites More sharing options...
Rare Scottish Tree Badger Posted July 16, 2005 Author Report Share Posted July 16, 2005 ...but think about a tired motor that's getting low on compression; it's a bitch to start cold but when warm it fires right up because the piston/rings have expanded, so it's got a tighter seal and numerically higher compression... 393134[/snapback] Good point. Rare. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.