Won't start!!!

My 04 450 wouldn't start a few weeks back so I change the plug and it fires right up. Then I go to the track and ride only one... (1).... day with no problems. The next week I cranks up, I ride a few laps, come in to rest, then the damn thing won't start.

What is up with this thing?!?

Any body wanna trade for a WR450? :excuseme:

time for a valve adjustment - :excuseme:

Oh yeah... forgot to metion... just had valve adjustment about 2 months ago

With the weather changing (higher temps/higher humidity), are you sure you're not running too rich and fouling out the plug??? Have you reset your fuel screw to compensate for the heat/humidity?? just a guess

Now, Im no expert, but is the bike popping, or bogging? Jetting issue...

Its summertime now, time to lean it a little, theres plenty of jetting info already posted here! I just jetted mine an hour ago, and so far so sweet

I'll have to check my fuel screw. I have not touched it ever. I was already thinking it might be fuel related. The bike has always been harder to start on warmer days.

If you buy the JD jetting kit, it will make your bike rip! Good jetting can be acheived without it, but not without a lot of experimentation. He has already done it and done it very well. It has specific needles and settings for different altitudes, heat and humidity levels. As everyone else has mentioned regarding the warmer weather,warm air is less dense you need to make the fuel charge less dense also. Also if you buy nothing else, buy an adjustable fuel screw and learn how to use it. It is an easy thing to do and the results will make your bike run better every single ride. They are less than 20 bucks or so and take minutes to install. You adjust them every ride after they warm up. What part of TN? I will be in Brownsville/Jackson area and Nashville in July but not riding unfortunately.

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