2007 crf250r will not run
  • Duckhunter0690
    Posts: 3
    Joined: Mon Oct 12, 2015 6:04 pm

    2007 crf250r will not run

    by Duckhunter0690 » Fri Jun 10, 2016 9:05 pm

    Ok, got a 2007 crf250r . Replaced jug/piston, spark plug and filter. Done the break in procedure and running fine. Went to a race and about 30 mins, the bike started backfiring and finally died, aftera bout 20mins of kicking the bike finally started but backfiring, held throttle wide open and then the bike cleared up and ran fine for the rest of race. Took bike home cleaned up and put away, couple days later i got it out to ride and it will not start at all. I just installed new plug, cleaned filter, checked all timing marks, removed carb and cleaned everythn, valves are .15mm imtake, .28mm exhaust, have spark at the plug when pulled out. Everythn checks out as it should, HELPPPPP IT STILL WONT RUN!
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    JimDirt
    Posts: 2617
    Joined: Sat Nov 25, 2006 6:31 pm

    by JimDirt » Fri Jun 10, 2016 10:57 pm

    I am assuming the gas was FRESH and the old gas (while it sat for rebuild) was drained out , do you have one of those aluminum Vent Caps on the gas cap ??? , it is possible that the vent is sticking and creating a vacuum and the tank will not allow the gas to get thru the line to the carb

    Try riding it with the vent cap off (just use a vent hose so gas does not splash in your crotch *not fun* while riding) and see if that makes a difference , its possible that the Needle/Seat is sticking , or the float level is off for some reason , as well

    Did you replace the Pilot Jet ?? , spraying cleaner in it (if you don't have a wire tool to clean out the passage) will not always clean out any debris (you need to remove the Pilot Jet to clean it) , and from the sounds of it , revving it seemed to clear a blockage , so maybe remove the 17mm nut at the bottom of the bowl and see if any debris are in it , the debris could be getting sucked into the jet under load , then fall back down to the nut when you let off the gas or when the bowl fills and is not stirring up the debris

    If your carb bowl has a drain screw , then open the fuel valve and let it sit for a minute or so , then close it , then loosen the drain screw and let the gas drain into a pan/bowl , so you can see how much gas actually drains from the bowl , if it does not look like enough to fill the bowl , then your having a starvation issue under load , which would mean float or needle/seat , or even the fuel valve itself could be restricting flow as the rubber that is in it to shut off fuel flow does wear and could be restricting flow or clogging the valve with rubber

    It definitely sounds like a starvation issue , you just have to trace it out by eliminating each item in the system

    If it runs fine , then won't run or pops thru the muffler , then its usually a lean condition , so eliminating each part of the fuel system 1 at a time will locate the issue , but i am thinking it has to do with the vent cap (if you have one on it) or the bowl not staying full or not being full in the first place , either would allow the bike to idle fine , but once under load , when the fuel demand is higher , then either vacuum creates a issue or lack of fuel to the bowl or in the bowl does

    But that is what i would look at for causes first

    It still could be a ignition problem , but eliminate the fuel system as a cause first before messing with the electrical
    02 CRF450R
    06 CRF450X

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