05bansh Posted February 15, 2005 Report Share Posted February 15, 2005 Ok- I installed my Noss head the other day w/19 cc domes. I followed the installation process step by step. I torqued it down 5,10,15, then 20. I checked the compression, it was only reading 120psi. I should be around 170-180psi. So I thought maybe it just needed to be run for the o-rings to seal. So I started it up yesterday, it ran awesome!!! I let it warm up for 5 minutes, then I drove it around my neiborhood for another 5 minutes. It ran better than it ever has. So I pull it back into my garage and checked the compression again on both cylinders. Still, only 120 in both cylinders. What the hell?? The only things I think it could be is a faulty compression gauge (the gauge is brand new though)? Or when I installed the head I left the factory gasket on, and I also installed the o-ring too. Would that effect it? Or one of the o-rings could have came off when I was pushing the head down onto the studs. Any sugeestions? Thanks in advance, sorry for the long post! Quote Link to comment Share on other sites More sharing options...
RBD Posted February 15, 2005 Report Share Posted February 15, 2005 It's probably your compression gauge. Unless it is a good quality gauge like a Snap-on and well kept, the gauge may not be giving you true readings. Also when using a compression gauge you need to hold the throttle wide open and kick the engine over very briskly. It also helps to remove the other cylinders spark plug. Ron Quote Link to comment Share on other sites More sharing options...
banshdog Posted February 15, 2005 Report Share Posted February 15, 2005 I'm thinking along the lines with RBD.... 1. Did you hold the throttle open? 2. How many times did you kick the bike over with the throttle open? Quote Link to comment Share on other sites More sharing options...
sredish Posted February 15, 2005 Report Share Posted February 15, 2005 what's your elevation? it's probably the gauge. if they're both correct, then that's good. maybe take it down to an auto shop and see if they'll check it for you with their expensive unit. Quote Link to comment Share on other sites More sharing options...
dlnoss Posted February 15, 2005 Report Share Posted February 15, 2005 Also, the part of the guage that screws into the dome needs to be the same length as the spark plug threads. If it's just a short stub that screws into the spark plug hole it will give a false low reading. You didn't leave the head gasket on did you? It wouldn't make that much difference in compression but it's not something you want to do. If the head wasn't sealing properly, you would probably have other symptoms like leaks, white exhaust, not running good, etc. Give me a call it you want. I doubt you will have 170 - 180 in Salt Lake but it should be more than 120. -David Quote Link to comment Share on other sites More sharing options...
05bansh Posted February 15, 2005 Author Report Share Posted February 15, 2005 I'm thinking along the lines with RBD.... 1. Did you hold the throttle open? 2. How many times did you kick the bike over with the throttle open? 323814[/snapback] No, I didnt hold the throttle open. I kicked it over probably about 10 times, just until the needle on the gauge stopped moving. Also, the part of the guage that screws into the dome needs to be the same length as the spark plug threads. If it's just a short stub that screws into the spark plug hole it will give a false low reading. You didn't leave the head gasket on did you? It wouldn't make that much difference in compression but it's not something you want to do. If the head wasn't sealing properly, you would probably have other symptoms like leaks, white exhaust, not running good, etc. Give me a call it you want. I doubt you will have 170 - 180 in Salt Lake but it should be more than 120. -David 323821[/snapback] The part that screws into the dome is pretty close to the same size of a plug. I got the gauge from napa. Yes, I did leave the head gasket on. Should I take the head off, and take the head gasket off? I am almost positive I have a good seal, like you said there would be white exhaust, not running good, etc. It ran awesome when I started it... Quote Link to comment Share on other sites More sharing options...
richwuest Posted February 15, 2005 Report Share Posted February 15, 2005 Yes, take the head gasket off. The O-rings are what create the seal with the aftermarket heads. Having the head gasket in there is just raising the head which is lowering your compression slightly, and giving you another point for possible failure. Quote Link to comment Share on other sites More sharing options...
05bansh Posted February 15, 2005 Author Report Share Posted February 15, 2005 K- I checked out the length of the gauge that screws in the dome, its slightly shorter, not alot, but a little. I checked the compression again holding the throttle open, and it came up with 140psi. Still a little low, but better. Any other suggestion? Quote Link to comment Share on other sites More sharing options...
05bansh Posted February 15, 2005 Author Report Share Posted February 15, 2005 I decided to go ahead and take the head off. So should I take the factory head gasket off and just use the o-rings for the seal? And also should I use any type of liquid gasket/head sealant? Quote Link to comment Share on other sites More sharing options...
zilladude Posted February 15, 2005 Report Share Posted February 15, 2005 Ditch the stock gasket, & just use a little grease to hold the o-rings in place. The directions say to put a little sealant on the stud threads. Quote Link to comment Share on other sites More sharing options...
squish Posted February 16, 2005 Report Share Posted February 16, 2005 I did the same thing and forgot to take the head gasket off. Made a big difference when I took it off. Pet. jelly works good to hold the o rings. Quote Link to comment Share on other sites More sharing options...
Justintoxicated Posted February 16, 2005 Report Share Posted February 16, 2005 I did the same thing and forgot to take the head gasket off. Made a big difference when I took it off. Pet. jelly works good to hold the o rings. 324079[/snapback] make sure you hodl the throttle wide open! thats your problem right there! Quote Link to comment Share on other sites More sharing options...
05bansh Posted February 16, 2005 Author Report Share Posted February 16, 2005 How does holding the throttle open give you a better reading? Quote Link to comment Share on other sites More sharing options...
banshdog Posted February 16, 2005 Report Share Posted February 16, 2005 How does holding the throttle open give you a better reading? 324580[/snapback] It opens up the carbs and allows air to flow into the cylinders. Without the throttle open, air flow is restricted. Less air in the cylinders = lower pressure and a low reading. Quote Link to comment Share on other sites More sharing options...
05bansh Posted February 21, 2005 Author Report Share Posted February 21, 2005 Alright, I took off the factory gasket, re-installed the noss head, made sure all of the o-rings were in place, and even used a thin film of liquid gasket on the seal. The bike ran damn good! The compression is reading 150psi. Higher than its been so far, but still not high enough. Any other suggestions? Quote Link to comment Share on other sites More sharing options...
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