Dr. Overkill Posted March 31, 2009 Report Share Posted March 31, 2009 Gang, First, and main question: what is a normal cylinder compression on a stock engine? Range from what to what? I assume someone has posted it on BHQ (probably many times) but I sure as heck can't find it easily. I have an '02 bike that the PO said he had the top end done on at some point. I don't know whether that's the first time it had been done or more. Is there any reason that would that alter the expected compression readings? Second... For the first time since I've owned it, it did NOT want to start up at the beginning of our trip to Glamis last weekend. Took a good 60 kicks and when it did show a little sputter to life, it just didn't want to hang on. It's always been super touchy about any throttle when it's cold (and always requires choke on the 2nd click for several minutes, unlike my other 2 Banshees which required only one click and then immediately off after it's running). So needless to say, once it started to sputter, giving it any gas killed it. New plugs didn't help. The plugs that were in it were a little oily around the threads, but the electrodes looked fine. Until about the 60th kick or so, when it finally kicked over... After that, the bike ran pretty much alright,, but there were some things about its sound while riding that just weren't quite the same. I couldn't pinpoint it, as it's my wife's bike and I haven't really logged enough time on it to say, but I just know it sounded different. There were some times when it bogged a bit when taking off and required more gas to get going. It did start up fine the rest of the trip, even the next morning when stone cold. I haven't had time to look at it yet, but I'm planning on checking the cyl compression and ignition spark next weekend. Just need to know what to look for in compression, aside from a significant difference from one to the other cylinder. (I don't have a leakdown tester and don't feel like making one just for this so I'm just gonna go with the basic compression and spark tests first to rule those out before looking further). Thanks! Quote Link to comment Share on other sites More sharing options...
vulvafan537240 Posted March 31, 2009 Report Share Posted March 31, 2009 stock compression should be around 120psi depending on elevation and should have no more than 5psi difference between the two cyls. have you done a plug chop on it? Quote Link to comment Share on other sites More sharing options...
Dr. Overkill Posted March 31, 2009 Author Report Share Posted March 31, 2009 (edited) stock compression should be around 120psi depending on elevation and should have no more than 5psi difference between the two cyls. have you done a plug chop on it? Thanks! My bike is stored at about 1000-1500 ft elevation. No plug chop. Didn't even think of that this past weekend I wouldn't go so far as to actually try to cut the plug open as I've seen some people here do, but I could have at least taken a look at them after a hard WOT run and killing the engine. Mebbe next time, if I don't get it figured out before then. Edited March 31, 2009 by Dr. Overkill Quote Link to comment Share on other sites More sharing options...
uwenr Posted March 31, 2009 Report Share Posted March 31, 2009 Gang, First, and main question: what is a normal cylinder compression on a stock engine? Range from what to what? I assume someone has posted it on BHQ (probably many times) but I sure as heck can't find it easily. I have an '02 bike that the PO said he had the top end done on at some point. I don't know whether that's the first time it had been done or more. Is there any reason that would that alter the expected compression readings? Second... For the first time since I've owned it, it did NOT want to start up at the beginning of our trip to Glamis last weekend. Took a good 60 kicks and when it did show a little sputter to life, it just didn't want to hang on. It's always been super touchy about any throttle when it's cold (and always requires choke on the 2nd click for several minutes, unlike my other 2 Banshees which required only one click and then immediately off after it's running). So needless to say, once it started to sputter, giving it any gas killed it. New plugs didn't help. The plugs that were in it were a little oily around the threads, but the electrodes looked fine. Until about the 60th kick or so, when it finally kicked over... After that, the bike ran pretty much alright,, but there were some things about its sound while riding that just weren't quite the same. I couldn't pinpoint it, as it's my wife's bike and I haven't really logged enough time on it to say, but I just know it sounded different. There were some times when it bogged a bit when taking off and required more gas to get going. It did start up fine the rest of the trip, even the next morning when stone cold. I haven't had time to look at it yet, but I'm planning on checking the cyl compression and ignition spark next weekend. Just need to know what to look for in compression, aside from a significant difference from one to the other cylinder. (I don't have a leakdown tester and don't feel like making one just for this so I'm just gonna go with the basic compression and spark tests first to rule those out before looking further). Thanks! Sounds like the gas was left or pingel leaked at some point and leaked into the cases, it will be a bitch to start but once it cleans out it will be fine. Mine did the same thing when we went to Glamis for presidents weekend Quote Link to comment Share on other sites More sharing options...
Dr. Overkill Posted March 31, 2009 Author Report Share Posted March 31, 2009 Sounds like the gas was left or pingel leaked at some point and leaked into the cases, it will be a bitch to start but once it cleans out it will be fine. Mine did the same thing when we went to Glamis for presidents weekend YES! I did forget to turn the petcock off between trips. Strange, though, because I replaced the needle valves about two trips ago, so shouldn't that prevent that from happening? Hmm, maybe I was just imagining the running-funky stuff, over-sensitized to every little thing after it was such a biotch to start.... Quote Link to comment Share on other sites More sharing options...
Dr. Overkill Posted March 31, 2009 Author Report Share Posted March 31, 2009 BTW, could fuel have gotten into the cyls and down past the rings? Would take a pretty good leak to get there, no? Probably a good idea to change the gear oil anyway... Quote Link to comment Share on other sites More sharing options...
uwenr Posted March 31, 2009 Report Share Posted March 31, 2009 BTW, could fuel have gotten into the cyls and down past the rings? Would take a pretty good leak to get there, no? Probably a good idea to change the gear oil anyway... its a twin one was prob up and it could go right past it. with the bouncing around wouldnt matter how new the needle is it will get by. No need to change the oil it two separate chambers. The easiest way to start it when they do that is pull start it, I had to pull mine about 1/4 mile before it cleaned out enough to run on its own. Quote Link to comment Share on other sites More sharing options...
Dr. Overkill Posted March 31, 2009 Author Report Share Posted March 31, 2009 its a twin one was prob up and it could go right past it. with the bouncing around wouldnt matter how new the needle is it will get by. No need to change the oil it two separate chambers. The easiest way to start it when they do that is pull start it, I had to pull mine about 1/4 mile before it cleaned out enough to run on its own. I was thinking that it shouldn't leak fuel while it's sitting parked in between trips, but then I remembered that towing it would bounce it around some, probably enough to slosh gas around in the bowl and possibly send some into the intakes. Quote Link to comment Share on other sites More sharing options...
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