jonnyb Posted May 16, 2008 Report Posted May 16, 2008 Ok I'm a pain in the @ss, I know this. I got a different compression tester(Mac Tools) vs no named murreys. Did my test with both plugs off cold first and got about 149 on the right and 145 on the left. Then tried it warmed it up for about ten min at idle. Got about 139 on the right and 135 on the left. I thought it was higher when its hotter. Oh well I guess its better then thinking it was 125 right. Quote
Bansh-eman Posted May 16, 2008 Report Posted May 16, 2008 so what exactly is the question? just should it have gone up when hot? Quote
jonnyb Posted May 16, 2008 Author Report Posted May 16, 2008 Whoops yup thats what I was getting at. Does it sound right. Quote
Wildcardracing Posted May 16, 2008 Report Posted May 16, 2008 Yup, cold air is more dense than hot air. Quote
jonnyb Posted May 16, 2008 Author Report Posted May 16, 2008 So compression is higher at at cold or hotter? Also does compression sound right? My mods are K&N filter, boyenson Dual stage carbon fiber reeds, Boost Bottle , tors removel, rejected, trail port, compete rebuild (rebuilt stock crank trued & welded, seals, gaskets, bearing top and bottom, top end kit .30 over, and head saved 60 thousands off. Quote
Wildcardracing Posted May 16, 2008 Report Posted May 16, 2008 If your head had .060 shaved off then they had to rechamber it for squish clearance, so 145ish could be right depending on how much squish they set and your elevation. That is a good compression number for premium pump gas, and the cyls are only off by 4lbs which indicates it is a faily healthy top end. I like to see them within 5lbs of each other. Quote
dajogejr Posted May 16, 2008 Report Posted May 16, 2008 Your compression should be a few PSI or so warm. When the motor is warm, parts expand...namely the cylinders and rings to seal better. Howvever...I don't think your motor is even broken in yet... Are you checking the compression the correct way? Holding the throttle wide open, kicking 20 to 30 times until the gauge has stopped going up? The first few kicks will net you a lot, after that...each kick might only give you 2 to 3 PSI.... Again...I know you want to get rolling with this bike, but without knowing the cc size of the head (Dan Hull would know) and how much squish you have....there is NO WAY anyone can tell you what the correct cranking PSI should be. Quote
Wildcardracing Posted May 16, 2008 Report Posted May 16, 2008 I only told him it could be right depending on the squish clearance and chamber work. Quote
dajogejr Posted May 16, 2008 Report Posted May 16, 2008 I only told him it could be right depending on the squish clearance and chamber work. I misread your post. I thought you were telling him yup....it should read lower PSI when it's warm as opposed to being cold... Quote
jonnyb Posted May 16, 2008 Author Report Posted May 16, 2008 When the motor is warm, parts expand...namely the cylinders and rings to seal better.Howvever...I don't think your motor is even broken in yet... Your probley right, only done 5 heat cycles now and road it about two miles. Just wierd that it went down when it was hot. Are you checking the compression the correct way? Holding the throttle wide open, kicking 20 to 30 times until the gauge has stopped going up? The first few kicks will net you a lot, after that...each kick might only give you 2 to 3 PSI Yup I held the throttle open both plugs out, and kicked it about 20 times. Again...I know you want to get rolling with this bike, but without knowing the cc size of the head (Dan Hull would know) and how much squish you have....there is NO WAY anyone can tell you what the correct cranking PSI should be Your probley right again you know where more than this newb. I do want to get rollin though. Was supposed to ride this weekend at mio but I'm going to wait. I just hope that I get up to mio next weekend. Sorry to ask you guys so many questions but I don't want to mess anything up. I'm not rich so I can't do a rebuild everyyear. I appreciate all your guys help, and dajogejr you've been a good help. Quote
dajogejr Posted May 16, 2008 Report Posted May 16, 2008 It's not a big deal...the real issue is the man that knows the most about your motor can't be gotten a hold of...and I'd hate to be the one to tell you the wrong thing.... Quote
jonnyb Posted May 16, 2008 Author Report Posted May 16, 2008 (edited) True that man, I hear yah. I just so dam exited Dan Did my motor, just wish I had the money to just drop the bike off and just say giter done. But I'm poor folk.lol Oh well at least I got a bike. Edited May 16, 2008 by jonnyb Quote
dajogejr Posted May 16, 2008 Report Posted May 16, 2008 Believe me, I know what you mean. In 06 when I built my 4 mil cub on gas I didn't tune or dyno run it...went all the way to Silver Lake, it had a base gasket leaking, a broken up flywheel and the center of the jug had a dip in it...sucking coolant. All the way to the dunes, never left the parking lot. Last year, new 10 mil on alky, two trips to the dunes, April and Memorial day...made 5 to 6 passes each trip...smoked a Stator one time, Head orings the next due to incorrect domes. But when I finally did get to ride the bike, both motors....it was well worth the wait. When I'm going to the track, the night before...I can't sleep I'm like a little kid on Christmas eve.... I know what you're going through!!! Quote
Wildcardracing Posted May 16, 2008 Report Posted May 16, 2008 It's not a big deal...the real issue is the man that knows the most about your motor can't be gotten a hold of...and I'd hate to be the one to tell you the wrong thing.... That's a damn good point, also my experience has been that they always read a few pounds lower warm as oppossed to cold. That was the only real ? asked in the original post, later he asked about the #'s and that depends on info we don't know. I always double check compression after the engines broken in good. Jonny i hope shee runs awesome for ya bud. Quote
jonnyb Posted May 16, 2008 Author Report Posted May 16, 2008 Low ends boggy but after that It's a whole different experience dam its fast and didn't go past half throttle yet. It wanted to pull a wheelie in forth Quote
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