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View Full Version : Someone tell me whats wrong with my bike


MudBug
08-31-2009, 06:52 PM
85 Big Red 250. cleaned the carb, adjusted the clutch, oil change. and the thing still runs like crap. sometimes it idles perfectly, while 5 minutes later it could cut out. It backfires like CRAZY. every time I let off the gas "put put POW" im thinking valves and rings. what do you guys think??
beets442
08-31-2009, 07:03 PM
Try starting the bike in the dark and see if the plug wire is arcing somewhere or check points, contacts. Beets
Lukeatc185
08-31-2009, 07:04 PM
does it smoke? is it easy to start? if so prolly not compression. could be valve ajustments or timing chain could be streched a little bit. backfire is usualy a timing or a valve ajustment from what i experience.
willrideanythin
08-31-2009, 07:35 PM
CDI Could do it.
Lukeatc185
08-31-2009, 07:38 PM
cdi unit? from what i have caught from advice on here is that the cdi unit either works or it does not. do you mean the smaller magnito with the cap marked CDI? his spark timing could also be slightly off if thats what you meant.
atctim
08-31-2009, 07:55 PM
could be out of time - or the pick up coil may need adjusted (advance or retard)
MudBug
08-31-2009, 08:23 PM
after a few rides with the new "Lucas" oil in, it seems the backfiring problem is getting better. but, it still feels as if the carb is dirty again, when I only cleaned it yesterday. It kinda bogs when I quickly hit the throttle.
Lukeatc185
08-31-2009, 08:26 PM
i dont see how some higher quality oil will reduce backfire. go with atctim his advice is golden. backfire is moreso related to spark timing or valve timing.
oscarmayer
08-31-2009, 08:58 PM
oops wrong motor. was thinking of a 200es. my bad.

i bet it's the cam chain tensioneer or chain itself.
litebulblsc
08-31-2009, 09:36 PM
Put a new spark plug in it
Dirtcrasher
08-31-2009, 10:18 PM
OP - "I'm thinking valves and rings"

Sounds fuel related to me. Backfiring means there's fuel, unburnt fuel.........

Is the choke closing fully??

As far as valves and rings - they can be tested easily.

Allot of times it's the little stuff that stumps ya :beer:
Race Demon
08-31-2009, 10:33 PM
Have you checked to see if you have an air leak from carb to head, spray a little carb cleaner around the intake and carb boot with the bike at an idle :confused:
atc500x
08-31-2009, 10:42 PM
Valve clearance....
Erics350x
08-31-2009, 10:57 PM
Its loading up like D.C. said, it could be a # of things causing it. Start by checking the valve clearance, timing, fuel cap vent, replace the plug, and clean and adjust the carb to stock specs. It sounds like alot of work but it can be done in a couple hours and prolly needs it anyway. How long has it been since the air filter was cleaned or replaced?
bonkers_200s
08-31-2009, 11:15 PM
Small things first, check the e clip in the throttle needle.
Vealmonkey
08-31-2009, 11:24 PM
Check for airleaks around the intake and exhaust.
MudBug
09-01-2009, 10:17 AM
I clean and oil the air filter almost every 2 weeks or so, but it do have a 3/4 inch rip in it. and I will check today on the leaking around the intake. when I put it back together , I noticed that everything didnt fit snug so maybe it leaked. Thanks for the tips guys, ill get back to you on this one.