biggun6ss Posted July 21, 2005 Report Share Posted July 21, 2005 I have a shaved head and I am around 3200 ft. What is a good compression? My buddy has stock motor except for pipes and his was 80 psi. My other buddy has a ported motor and his was 100 psi. Are these numbers too low or are they about right. Also do you need a special compression tester or is one for a car alright? Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted July 21, 2005 Report Share Posted July 21, 2005 sounds like rebuild time to me. maybe dlnoss o the site will stop in and let u know. he is owner of noss head. he will def know what you should be at. Quote Link to comment Share on other sites More sharing options...
chris642 Posted July 21, 2005 Report Share Posted July 21, 2005 I have a shaved head and I am around 3200 ft. What is a good compression? My buddy has stock motor except for pipes and his was 80 psi. My other buddy has a ported motor and his was 100 psi. Are these numbers too low or are they about right. Also do you need a special compression tester or is one for a car alright? 395220[/snapback] those numbers are extremely low, these engines need at least 100PSI to even run. Either your budies need to get a new compression tester, or they are somehow not doing it right. The tester for the car works fine, make sure you have one that screws in, the ones you hold to the spark plug hole dont clear the gas tank, and it would be impossible to do by yourself becasue you need to kick the bike over like 20 times . a stock engine should be around 130PSI, we cant tell you how much compression a "shaved head" will give you since you can mill all diffrent ammounts off. I can see a ported motor having 100PSI if he didnt have his head modded or got a billet head with smaller domes, when you change the port timing, the compression specs change. Quote Link to comment Share on other sites More sharing options...
hittintrees srh Posted July 21, 2005 Report Share Posted July 21, 2005 I have a shaved head and I am around 3200 ft. What is a good compression? My buddy has stock motor except for pipes and his was 80 psi. My other buddy has a ported motor and his was 100 psi. Are these numbers too low or are they about right. Also do you need a special compression tester or is one for a car alright? 395220[/snapback] Dude i live in slc utah( ) , and i have a ported motor, my compression w/ 21cc. domes was around 120psi. 80psi is WAY too low- that bansh must need new rings, or a new comp. tester. Just remember to hold the throttle wide open when you test it. Then kick an kick and kick- till the pressure stops rising. Quote Link to comment Share on other sites More sharing options...
brugal Posted July 21, 2005 Report Share Posted July 21, 2005 80 psi,your boys bike must run like shit nah ,cant be ,you must be checking it wrong.But, if you check properly and get those same numbers ,both of your buddys motors need to be rebuilt. Quote Link to comment Share on other sites More sharing options...
dlnoss Posted July 21, 2005 Report Share Posted July 21, 2005 At that elevation, it should be around 110psi. Make sure the compression tester threads into the head the same amount as the spark plug. That can change the reading by 10 to 20 psi. Squirt a little oil in the spark plug hole and check it again. It will increase some but if it increases a lot, like 20 - 30 psi, it's probably top-end time. An aftermarket head or shaving the head can help offset the lost compression of the higher elevation. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted July 21, 2005 Report Share Posted July 21, 2005 Just remember to hold the throttle wide open when you test it. Then kick an kick and kick- till the pressure stops rising. 395277[/snapback] Remember to take a cold reading as well as a warmed up reading too...there will probably be a slight difference. Your final reading should be with a warmed up engine...and holding the throttle wide open as mentioned above... Quote Link to comment Share on other sites More sharing options...
biggun6ss Posted July 21, 2005 Author Report Share Posted July 21, 2005 Don't know if they had the throttle wide open but I will make sure it is when I check mine. The guy with the ported motor has a cool head with 18 cc domes. I thought that 80 and 100 sounded low. Will tyr it and see. Thanks for the info Quote Link to comment Share on other sites More sharing options...
dajogejr Posted July 21, 2005 Report Share Posted July 21, 2005 Way low for that elevation and 18cc's. Courtesey of Mr. Noss...look at the bottom of this page for a "Fresh Motor" PSI spec based on dome size and elevation. Props to Dave Noss for a great product and support!! http://www.nossmachine.com/banshee_heads.htm Quote Link to comment Share on other sites More sharing options...
biggun6ss Posted July 23, 2005 Author Report Share Posted July 23, 2005 Tested all three shees today. As i said we are at about 3000 ft elevation. Its around 90 degrees. Tested all shees with WOT(didnt make a diff in psi reading ). I let mine run about 5 min before testing. Tester is good and it threads in the same as the plug. 2003 LE No head mods 80psi on both cyl 2004 LE Cool head w\18cc domes 100 psi on both 2005 shee shaved head .030 90 psi on both (mine) They all run well but I dont know what a bad one runs like either. Does this seem low, or is it right. I have no clue. If it is low I want to rebuild before it completely goes. When i say run good I mean my shee is about 3-4 quads behind a piped, camd, yfz 450 until top end then i start to catch him. Y do you need throttle wide open? Quote Link to comment Share on other sites More sharing options...
switchblade Posted July 23, 2005 Report Share Posted July 23, 2005 They all sound low to me. I would try to barrow another compression tester from a friend and see what is says. It is hard to believe that a 05 would have that many hours on it that is would need a top end. If a defferent tester reads the same or close I would aopt for a new top end. Quote Link to comment Share on other sites More sharing options...
chris642 Posted July 23, 2005 Report Share Posted July 23, 2005 ya, spend 30 bucks or so on a good compression tester. all of them sound real low, i doubt it is just a coincident. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted July 23, 2005 Report Share Posted July 23, 2005 Y do you need throttle wide open? 395910[/snapback] To allow for as much air as possible into the chamber for a proper check. Normally..it's only a few PSI...but, it's in the book! Good thing is...they are all wearing pretty darn even, which is nice. When you say you let it run for 5 minutes...is that in idling or actually going out...riding it...and warming it up properly? Quote Link to comment Share on other sites More sharing options...
biggun6ss Posted July 23, 2005 Author Report Share Posted July 23, 2005 To allow for as much air as possible into the chamber for a proper check.Normally..it's only a few PSI...but, it's in the book! Good thing is...they are all wearing pretty darn even, which is nice. When you say you let it run for 5 minutes...is that in idling or actually going out...riding it...and warming it up properly? 395999[/snapback] I let it idle for about 5 min. Didn't have time to go out cus I was on my lunch break and I was a hungry mfer. I will buy a tester today and check mine again. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted July 23, 2005 Report Share Posted July 23, 2005 Word...man's gotta eat.. I'd take it for a good 5 to 10 minute ride, making sure it's fully warm... I really don't think you're going to gain more than a few PSI...which, is not even close to where you need to be! Quote Link to comment Share on other sites More sharing options...
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