is this a fuel or electrical problem?

07 yz450...about a month ago i removed a dynojet kit from the carb(installed by original owner) and installed oem parts...and the next time i rode the bike it kept in it would start first kick idle for a couple seconds and then die like the kill switch was try and turn the throtle slowly of normally it dies......i adjusted fuel screw the full range with no affect...went up and down 3 sizes on main and pilot and clip the full range effect....i took the carb off and carb cleaned it thoughly and blew air through everything...checked float level unplugged tps and kill switch independantly and together took off the gas cap incase it was some issue with that or the check causing it to valve vapor lock ..same thing....checked valve clearances and timing (even though it started first kick) drained the tank removed and cleaned petcock went to sunoco and got new fuel nothing changed same deal...i put the dynojet kit back in exactly as before when it ran fine...still same thing...after having the thing apart 7-8 times over a couple days...i had to walk away before stufing a rag in the tank and lighting it....a couple days go by bike sitting untouched...i pass it on my way to the mower and for the hell of it i kick it over starts second kick and able to rev stayed running ...acting normally so i set up the big 48" drum fan to keep it from over heating and cut some back it was still running and could be reved no ive put probably another 10 hrs on it with no problems and yesterday out of the blue it is now doing the same thing....but if i start it and as soon as it starts i get it above 3000 rpms and i set the idle at 3000 it will idle forever..and i can rev it no problems if i turn it down to 2950 it will stall like you hit the kill button...but start right back up first kick... is 3000 rpms some thresh hold in the electrical system/cdi/stator/coil or whatever?.....i mean like a 2 stage component and the low rpm portion is defective? just seems like 50 rpm difference wouldnt be a carb/fuel issue...not to mention it just started running right after just sitting a couple days..ive got a new coil/cdi/harness and carb coming thanks to GOOSE 07 YZ450F...but im wondering if i should pick up a stator as well.....:thumbsup:

My 2008 yz450f seems to be doing the exact same thing yours is. I've checked the same things you have also. It started during a harescramble over a month ago and I've been pulling my hair out since then trying to figure it out. Please let me know if the harness, carb or stator fixes it. Mine will start fine with the choke (high idle) then dies within seconds after turning the choke off.

Well I recieved a new oem stator today... Installed that same deal... Hopefully I'll get the rest of the stuff tomorrow... And do cdi -coil-harness-then carb ...Trying aftereach and let u know the outcome...if none of that does it my plan is to make a " moulatof motorcycle" out of it... Lol

Sorry about getting the carb out to you so late...

It's on it's way...

no problem... the wifes extra happy that she "has me " all weekend now..hahaha

I took my bike to a tech yesterday that is supposed to really know his stuff. He mentioned he was going to check the stator/flywheel/woodruf key among other things. I'll keep you posted

I had this exact issue with my 2008 and could not find a problem. Finally got rid of the gas in the tank and the 5 gallon jug in my garage and my problem was solved. I simply had bad fuel.I now use a different source.

Any updates? I'm super curious to see if you just replaced all the parts at once, or did it in steps to see where the true issue was hiding...

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