Cannondaleriders

after about 15 min of hard riding/racing, it starts to hesitate/bog when throttle is applied, to the point that it will shut off then not restart after about 5-8 min of fan running, once fan runs for that period of time it will start and run at a race pace for another 10-15 min and then repeat.
this has happened the last two times out.... i have changed nothing to facilitate this occurrence. i thought maybe a temp sensor, but i figured that when getting to hot it would shut the quad off like turning the kill switch, but that is not the case.... any input would be appreciated

Well first make sure coolant is flowing. You might have a stripped impellar. Check coolant level. Run it for a few minutes and be sure the top of the rad is withing 15 degress of the lower. If the bottom is cold and just the top gets warm its not pumping.
I hope its not getting so hot its hot seizing because then it may be to late for that piston and sleeve.
Can you see fuel flowing through the filter when it stalls?

its not seizing, after it shuts off, it turns over just wont start. do the aluminum impellers strip? i will check the other things when i get back to my shop tomorrow, i have another temp sensor, should i change it out?
i have never had a problem with riding in the heat before, can the fuel get to hot ?

Ive had a couple of occasions where long duration(several hours at slow speed) with race fuels in high heat caused the fuel to boil . You can easily tell because the fuel pump will squeal and nothing goes throught he filter. When the fuel started boiling it was gurgling out the vent tube and boiled like water on the stove . The fuel tank has a high r rating so once its gets hot it takes a very long time to cool down. I have add on fuel heat exchangers for when we go to the dunes again.
But like I said it would have taken several hours to get the fuel in the tank that hot .No way in just 15 minutes of riding.

One other thing Ill bet it is is the coil . I had a coil that would do what your describing. Once it got hot it had a weak spark . It made the quad start like crap when it warmed up . Do you have a spare you can drop in ?

What type of valve cover do you have?

Mine may have done just like Wistech described yesterday.No flow through fuel filter.Happened after a hour in 85deg heat 80% 1st gear slow riding.If I had disconnects I would blame them.When I looked in the tank fuel was rolling just like from return moving the fuel when pump is running and fuel is over top of return.Nothing at all going into the filter and fuel pump just screaming.Once cool it ran just fine.

yes i have a spare coil, i will try that, what about temp sensor?
and this is an updated motor