won't run when hot..? 05 450r

[gearhead400]

I first noticed this problem at croom a few rides after i got the bike. It has a rev max cdi, full LRD exhaust, k&n filter with no lid.
The problem seemed to happen when i was at slow(er) speed and high revs, rarely hitting the top of third. After it got real hot, it would start cutting out in the turns and backfiring. After about 1/2 - 1 minute of that it would start dying in the straights as well and would just cut out completely. If i let the bike sit for 5-10 minutes, i can ride it for another couple of minutes, just as strong as any other time and then the same thing would happen.

Not sure what the cause was, i went ahead and changed out the full exhaust and returned it to stock and re-jetted the bike. I raced an ssqsa race which was canceled at about an hour with absolutely no problems at all. I rode around my house a few times through over the week or two that i wasnt racing and didnt have any problems.

Well, i was just up in madison this past weekend racing pauls xc series and the same thing happened, a little less than an hour in. a looot of stop and go riding in sugar sand. When i would get on a straight with it popping a little bit, if i could get it going, i could pin the throttle and it would get up and go, full power! but as soon as my rpm's started to drop, pop pop, engine would cut out.

I havent been able to put my finger on it yet and say for sure what it is but i have some ideas.

The CDI could have a problem and i know everyone hates aftermarket cdi's (if it didnt come with the bike, it would still be stock!) when they go, they go. But it is electronics and they always seem to vary when they crap out.

I thought MAYYYYBE it could be the temp switch because the lite flickers like crazy when the bike is cutting out. but i unplugged it and nothing changed.

the only other thing i can think of is that it needs a valve job....?

any help would be great, although i doubt i'll have the $$ to fix this any time soon 

[IXIswamperIXI]

This is a LONG SHOT... and the more i think about it, the more I don't think this is it this, but I have had problems with exhaust running to close to a fuel line causing the fuel to vapor lock.  Just an idea, I am not familiar at all with a 450r as far as where the little fuel line runs.

[kawasakimojaverider]

i think you have a cdi box problem like you said

[TRX450R_Racer]

When is the last time you had the valves adjusted?

[gearhead400]

i couldn't tell you, i havent adjusted them. and i've rode the bike hard (for more than a thirty minute period) probably a dozen times now, probably less. The guy that owned it before me seemed to take care of it real well and was a skilled mechanic.

I dont think exhaust heat is the problem, but i have heard of that before!

[TRX450R_Racer]

If I was working on it the first thing I would do is adjust the valves.