400ex overheating please help

[dmaheryfz450]

hello guys i new to the forum i have a 400ex my problem is its going like a train for the first 1hr or so of riding then it wont rev and looser power im running crf450 chain air box lid removed fmf pipe keihin fcr carb 175main and 50pilot fuel screw 2 turns out and choke removed any help appreciated thanks heres a pic of it oh by the way there only about 30 hrs on fresh top end it was only bored slightly .20 over or something

[JOHNDOE83]

I had this same problem a few weeks ago, I was at a drag race and lost a main jet that I needed, I wound up running it a lil lean.

After my first three races, I gradually lost power, the leaness was making it run hot and the humidity that day made it worse as time went by.

What motor mods do you have? it may be just slightly on the lean side enough to make it heat up and lose power gradually like mine was.

I have video of my race, beating a highly modded yfz450...lol.

[dmaheryfz450]

what jet size do you recommend i sold my yfz because it keep blowing up lol

[JOHNDOE83]

go up on jetting a lil bit, Ill post some info for you on jetting.

[JOHNDOE83]

Heres a jetting thread I made.

http://www.exriders.com/vbb/showthread.php?s=&threadid=441780&highlight=johndoe83

[dmaheryfz450]

thanks buddy

[JOHNDOE83]

No problem, glad I can help, good luck.