i just got a used 2001 400ex and i was ryding it real hard racing cr250 and yz 250s and like 1hr of ryding it started to get real hot and i turned it off then it took me like 30 minutes to restart it and then it only rydes for 5 minutes i cant even get down the street with out it bogging out. I got an extended 2 year warranty and it gots a half tak of gas the oil is good and i checked the engine it looks like everything is good but what could be wrong with it??

 

what modifications do you have done?

 

well for one thing, if it is stock, good luck trying to beat a cr250. those are very very fast bikes. mine has the 440kit, fatboy4 pipe, jet kit and a k&n filter and i still cant beet a cr 250. I would try rebuilding the carb. i had the same problem with my ex and then it completly stoped running in the middle of a field and i had to have my buddy pull me home. i thought i blew it up cuz i was running the ***** of of it trying to keep up with him(400ex alot faster than mine). well anyway we got it home and i took the carb off hoping that would be the problem and the main jet was completely clogged up. the carb was a mess. so i just kleened it up and put the jet kit in it and it has run fine evercinse that. is it burning oil. if it is then it will need rebuilt. not to expensive, asuming it doesnt already have the big bore kit, you could get it bored out while you have the motor already tore down. well hope this halps you. just check the small things like the card it pays off. well, let us know how it works out

 

The suggestion that the main jet is clogged is a good one. It would mean you may be running too lean and that will cause the overheating..........which is why you had to wait 30 minutes to let it cool down. If the jet is severely clogged, the motor will overheat very quickly at any decent load. I have seen a race quad almost cook in 5 minutes of practice on a flat track with the jet too lean....not clogged up, just a bit lean.

Have you checked your plug to see what it looks like? If it is smoking a lot now, then you may have done some more serious damage......rings, valves and guides, cam, tappets etc. Motors do not like being heated to the point of seizing and with air cooling the 400 ex likes to have the mixture right to keep things in the correct heat range.

 

GET A PERFORMANCE CARB.