New Guy

[Crazy05]

Hi everyone. I lost some compression at Galmis this last weekend. I ran

straight 91 instead of 50/50. My kicking compresssion was 125Lbs. The

bike has a Dune port and and revs to 11-12K. My question is, does having

a motor that revs that high change the compression at high RPMs. I read on

here that you only need 91 up to 150lbs kicking.

 

Glamis was a blast. Awesome fireworks as far as the eye can see. I was

camped at Osborn and could see the fireworks down the washes and by the

store and al the way down ghecko.

[tonyown]

hum in my mind 91 octane is good enough for 125psi compression... if you'd be between 150-160 maybe there would be chance of detonation... I dont know why revving high would change compression if your setup is right...

[bansheefreak]

125 is good.. no matter how your motor revs.. as for race gas your just wasting your money with compression at 125 just run pump gas.. the main thing is to make sure you have numbers close to same in each cyl... is it running funny or something ??? why do you ask

[Crazy05]

125 is good.. no matter how your motor revs.. as for race gas your just wasting your money with compression at 125 just run pump gas.. the main thing is to make sure you have numbers close to same in each cyl... is it running funny or something ??? why do you ask

My compression dropped from 125-125 to 110-95. I was told to run 50-50. I read on here that it's not needed so I went to staight 91

My bike takes a shit and I'm wondering if it could be the gas. What if it is timed high enough to need 50-50? Could that be why my

builder Suggested the race gas mix? It ran fine for last season and part of this season. Maybe just time for rings??????

Edited January 18, 2007 by Crazy05

[okbeast]

Extra timing does "need" (I say that lightly) higher octane, but nobody knows the perfect #'s. Did you test it this last time warmed up?

[2003LimitedBanshee]

Testing warmed up versus cold makes little noticeable difference. To address your question you would have to be running quite a lot of timing to justify a 50/50 mix. Are you running a Dyna, timing plate etc? I would be concerned about a drop of 30 psi in that one cylinder after just weekend. The lack of octane, if it was needed, would cause other issues, but not likely a simple loss of compression with no other symptoms. What do the spark plugs look like? Color, deposits etc.

 

edit: Also, have you tested the bike to those RPMs. That would definitely be a revver if it does truly turn those RPMs. My other main question would be what kind of pipes are you running.

Edited January 18, 2007 by 2003LimitedBanshee

[Crazy05]

Testing warmed up versus cold makes little noticeable difference. To address your question you would have to be running quite a lot of timing to justify a 50/50 mix. Are you running a Dyna, timing plate etc? I would be concerned about a drop of 30 psi in that one cylinder after just weekend. The lack of octane, if it was needed, would cause other issues, but not likely a simple loss of compression with no other symptoms. What do the spark plugs look like? Color, deposits etc.

 

edit: Also, have you tested the bike to those RPMs. That would definitely be a revver if it does truly turn those RPMs. My other main question would be what kind of pipes are you running.

My pipes are the old style Shearers with all the section welds. My RPM's are confirmed on the dyno when I got it tuned. The timing I think is a timing plate mod but dont know for sure how many degrees. I think 4 or 5 but really dont know. I was told by my builder that the bike should be good for 3 seasons and would just need to be honed and ringed and would be good to go another 3. I dont think he knew at the time he told me that , that I ride more in 1 season than most do in three. 15 to 20 gallons a weekend. Spark plugs looked normal with the lower cylinder a little wet. Cocoa brown on the porcelain as far as I can see without cutting them open. Edited January 18, 2007 by Crazy05