honda dirt bike - high rev, then nothing after kick start

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kennydude · #1 Unread post by **kennydude** » Sun Apr 27, 2008 5:59 pm

Hey guys, my neighbour has an issue with his dirt bike. I dont know much, but he asked me what i thought.
when he startes it (kick start) it rev's mega high for probably 5 seconds, then dies out.

anythoughts? i figured it wouldnt be the battery, and possibility of the carbs going? am i far off ? am i semi right? hah, i bet there are a million other things it could be.

sorry i didnt get the year or the model.

thanks for your input !

BuzZz · #2 Unread post by **BuzZz** » Sun Apr 27, 2008 7:00 pm

Battery? on a Honda dirtbike? Must be an XR-L or one of the newer smallbore starter bikes...

Anyways.... if it starts, no matter for how long, it ain't the battery.

Depending on what bike it is, it could be a plugged jet in the carb, or a ripped diaphragm..... sounds like a carb problem. Something is preventing it from getting enough fuel to run. Will it idle with the choke on?

kennydude · #3 Unread post by **kennydude** » Mon Apr 28, 2008 3:46 am

i didnt get a great look at it, it was in the dark. i would assume the guy knew he needed to give some choke to help it start, and it rev'd like it had it on, but i physically didnt see him turn on the choke or turn it down.
carb tho hey?

BuzZz · #4 Unread post by **BuzZz** » Mon Apr 28, 2008 5:21 pm

It starts and revs up (even if uncontrolled) so it has spark, compression and at least some fuel all jivin' together at the right time. Then something makes it stop. It probably isn't jump out of time, then back into time to start again. Nor is it likely to suddenly lose and regain compression. Electricity is pretty reliable, it is there or it isn't.... it seems to be there... (there is a small possibility that the ignition cuts out when it revs up, but it's really small....)
So that makes fueling look awful guilty. It is getting some fuel at startup, either from the choke or the low speed jet circuit in the carb. Then it revs it's nutz off...... is the throttle stuck open? You might have to remove the airbox and look down the carb to see if the butterfly is open, if it's not, then one of the carb circuits is either blocked off or delivering too much fuel (like a mis-adjusted accelerator pump, if the bike has one), either condition (rich or lean) can make an engine run away depending on the air supply situation.

And that's about as close as we are going to get here with the information we have. Tell him good luck, eh.