RC51 woes

Started by Fast4fun, April 09, 2003, 11:48:33 PM

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I replaced my exhaust with a Jardine 2-1 and pcIIIr. The bike seemed to run well for the day I took it out of storage before the changes. After... it backfires and dies regularly. I took it in for a custom map just to find out that the front cylinder is low on compression. The mechanic believes it is probably a valve that needs adjustment. No surprise, I am over the suggested mileage limit for a full tune-up. I raced regularly last season without any problems. Just trying to make mild improvements for this season. Does anyone have enough experience with the RC to diagnose!? the problem. I am quickly getting into a financial windfall. If it is just a valve adjustment then I'm OK. If it's more...? I guess no one said racing would be cheap. But it sure is fun!
CCS Mid West EX #675
Tri 675


Do a leak test to see if/where the cylinder is leaking (do this after checking/adjusting valves). I have not had any problems with my RC, but I only have about 2000 miles on it.
Brian McLaughlin
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2 strokes smoke, 4 strokes choke


Adjust the valves and do a leak-down test. Also, make sure the PC3r is properly grounded. For grins, remove the PC from the system and see if your stalling/backfiring is affected.


You said it your self that its do for a full service.  DO it.  while your getting the valves serviced, have them do a leak-down on the head when their done.  I dought its major.
Did you check to make sure the header bolts are still tight?
CCS Midwest EX 501(RETIRED) E-mails welcome @: unforgivenracing@hotmail.com or, IM and e-mail me @: unforgiven_racing@yahoo.com also,
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Had the valves checked... they're ok. Still not holding pressure in the front cylinder. Must consider whether or not to invest the dime to rebuild. Suggestions are welcome.


Give it to me for free.

Seriously it can only be piston rings or valves. Pull the head and you'll know for sure.  But before you do that, a quick way to check rings is to squirt some oil in the spark plug hole and do a compression check.  If compression is up after squirting oil in the cylinder than it is a ring problem.  If compression dosen't change it is a valve problem.


Pulled the engine. There is some scoring of the cylinder. Having it bored 1/4 over with genuine honda pistons and new rings. Since I have it in pieces, I am looking for engine modification suggestions (Cams, porting, etc). See related thread. I will post the results. Even with the loss in compression It was pulling 117 hp on one dyno.
CCS Mid West EX #675
Tri 675