I'm working on an '03 CRF450R. When it came to me it would not start and gas was spilling out of the carb. I replaced the float needle and the carb no longer overflows. I was able to get the bike started, but the idle would randomly go from about 3000 RPM to about 500 and stall. There was a slapping noise from the engine so I checked the cam chain tensioner: it was all the way out. I replaced the cam chain today and now it is easier to start, but the idle is still erratic and I can't get it to restart once the engine is warm. Valves have been checked recently.
Suggestions?
'03 450R running rough - need suggestions
Started by
pablo83
, May 10 2012 05:21 PM
4 replies to this topic
Posted 10 May 2012 - 07:29 PM
Shawn_Mc, on 10 May 2012 - 06:10 PM, said:
The throttle plate on the slide is upside down.
Crap. I was careful to reassemble it the same way it was installed, but the bike came to me in poor running condition so maybe it was already like that.
Thanks, I'll check it in the morning.
Posted 12 May 2012 - 11:40 AM
I check the slide plate orientation today. It was correct (hole down as pictured). What else could cause this?
Posted 12 May 2012 - 01:26 PM
Air filter oil in one of the air jets?
Id douche the carb really well (clear with compressed air) and start over with the jetting at stock settings. Make sure all the vent lines are clear. Check the hotstart cable and make sure it's not seized with rust and that it seating. Happens all the time.
Is there anything done to the engine? High compression piston?
If it starts cold, but gets tougher when hot, it sounds rich. But I wouldn't rule out the intake valves either. They can go bad from a reshim in 5-8 hours of run time when the coating is completely gone. For a trail guy that could be one day of plunking around. Also the RPM isnt really the culprit. Its a combo of dirt, powdered metal seats and the coating coming off that kills the valve face.
You've got the carb out (if not, at least the tank is out) so at least cover the base and check the valves yourself. Ive seen them do weird shit when the lash gets down to .002".
Id douche the carb really well (clear with compressed air) and start over with the jetting at stock settings. Make sure all the vent lines are clear. Check the hotstart cable and make sure it's not seized with rust and that it seating. Happens all the time.
Is there anything done to the engine? High compression piston?
If it starts cold, but gets tougher when hot, it sounds rich. But I wouldn't rule out the intake valves either. They can go bad from a reshim in 5-8 hours of run time when the coating is completely gone. For a trail guy that could be one day of plunking around. Also the RPM isnt really the culprit. Its a combo of dirt, powdered metal seats and the coating coming off that kills the valve face.
You've got the carb out (if not, at least the tank is out) so at least cover the base and check the valves yourself. Ive seen them do weird shit when the lash gets down to .002".
