2003 CRF 450 (engine issue)

volcati
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volcati
Edited Date/Time 1/26/2012 5:32pm
I quit riding bike a month ago after it started backfiring a lot and was a pain in the ass to start after riding.

I went to start it today...took a while to get started but it started. When I gave it throttle the bike was doing tiny backfires. Kept it going for about 2 minutes and still same issue. Then shut it down.

Is this valves usually? That's about all did. If it is valves...possibly...what all should I do the engine if I'm going to tear apart? Is there standard points I should change. Gaskets of course, valves, rods?? Do the whole thing?

Can you just buy a refurbished head? Is that easier?


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CamP
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CamP 7/3/2009 8:13pm
7/3/2009 8:13pm
Hey Mike, make sure the pilot jet is clear before you do anything. Run a single strand of throttle cable through it to make sure it is clear. If the pilot is clear, check the intake valve clearance next. If the valve clearance has zeroed out, I would suggest that you buy a new 07/08 head and all new OEM valves/springs from Service Honda. It will cost about $500 for a complete head which isn't much more than trying to refurbish the old one and the newer head design has improvements that make it a worth while upgrade. If the intake clearance is good and the pilot is clear, then you have an ignition problem.
xnationalwrench 7/4/2009 6:17am
7/4/2009 6:17am
CamP wrote:
Hey Mike, make sure the pilot jet is clear before you do anything. Run a single strand of throttle cable through it to make sure it...
Hey Mike, make sure the pilot jet is clear before you do anything. Run a single strand of throttle cable through it to make sure it is clear. If the pilot is clear, check the intake valve clearance next. If the valve clearance has zeroed out, I would suggest that you buy a new 07/08 head and all new OEM valves/springs from Service Honda. It will cost about $500 for a complete head which isn't much more than trying to refurbish the old one and the newer head design has improvements that make it a worth while upgrade. If the intake clearance is good and the pilot is clear, then you have an ignition problem.
Another thing you can use is the smallest acetylene tip cleaner to clean the pilot jet if you don't have spray carb clean but have disc brake cleaner this will work also.
FlickitFlat
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FlickitFlat 7/4/2009 6:28am
7/4/2009 6:28am
I had a friend with an 2006 that did the same thing. We found that the spring steel spring on the Hot Start broke. It is an easy check. Look in your manual but it is on the shifter side of the motor under a cover toward the back of the head. Two bolts hold it under the cover and then it slides out. Worth a look. It would have saved my friend $1000's if he would have found it instead of tearing down his motor.
CamP
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CamP 7/4/2009 6:52am
7/4/2009 6:52am
Yes, a hanging open hot start can also cause similar symptoms.

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volcati
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volcati 7/4/2009 12:34pm
7/4/2009 12:34pm
Awesome.

Thanks all for the advice.

Hey Cameron....me and the wife are looking at moving to Austin next spring. She just got back from a look and see trip asmost her side of the family live there. I love the place and with my nomadic life I'm always up for anywhere.

I'll check the hot start. And then every thing else.
CamP
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CamP 7/4/2009 3:39pm
7/4/2009 3:39pm
Right on. Austin is a cool town. There are a couple of good tracks down there too.

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