03 450 wont stay idling and hi piched pops just started

my 03 wr450 just started acting up. the temperature has dropped lately to about 45-55 degrees outside and it seems to have been doing it since its got colder out. also for some reason it seems to stay idling high when im going down hills. i think that might have had something to do with hot start lever being messed up though. i know the motor is getting tired so im wondering if it has something to do with that. it was been running a tad rough for a little bit now but no real signs of metal or anything in the oil so i have just been running. what else would cause the higher piched popping(doesnt seem like a full on backfire, just a louder sputtering). its never really done that until yesterday. thanks for any advise.

Clogged pilot jet?

Yes, your hot start issue would cause your symptoms! Fix it.

is the little plastic piece that holds the hot start cable to the carb cracked? Mine was and I replaced it with an aluminum one

no its not cracked. the other day i went out to try and see what i could find and it wasnt. everything looked good on the outside. but now it wont even stay running unless i am giving it choke or throttle. i just took the carb off tonight so im going to take it apart and look at the inside. im thinking a clogged jet like kenshaw720 said or maybe something to do whit the float.

turned out to be a tight intake valve!

what causes valves to tighten up. because i just had them adjusted in june when i got the bike and again the intake valve was a little tight.

Worn valves, over-reving, worn head, you name it! How many hours on the motor? Any head work done already?

High perf 4 strokes are not the happiest bouncing off the rev limiter, though lots of people like to do this. Especially with the Yamaha titanium valves will you see tightening if you rev a lot.

Time for a top end rebuild. Welcome to high strung 4 stroke life!!!!

Often, grit gets past the airfilter and it grinds the hard coating off the valves. This causes the valves to wear and recede into the head. Being the hard coat is gone, re-shimming is only a stop gap fix as the receding continues. Only fix is new valves.

yah i figured, im still new to bike so im trying to learn all this stuff as i go. my mechanic told me that its about time for a motor job, so i think thats going to be my winter project. thanks for all the info guys!

trevor~

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