popping,sputtering, and looseing power(450r)

[Stealth450r]

i bin having problems with my r for a couple of months now and cant figure out anything. first off evertime i hit an bump it looses all power until i get off the gas, but i cleaned my carb and all ecetrical and now it is once ever 20 mins. k\now its starting to pop/backfire then looses power. also my anti-freeze over flow is spilling every where. my quad has an all stock engine. if you can help in any way i would appreciated, cause i have a race in 2 weeks and i need this thing run good.

thanks

[mojoe2878]

i had a similar problem with my yz250f mx bike , it turned out to be that water deposits had colected in the water ports in the engine from using hard water (something to do with minerals in some water) the minerals collect to the aluminum fast and cloged up my ports and wasnt lettin the water circulate fast enough through the radiator to cool it off. i had to flush the engine out and then it was ok again. if you dont use it already i would suggest some stuff called blue ice radiator fluid, can get it at most cycle dealerships, this stuff is awesome, has a boiling point of twice the temp as regular antifreeze, its already mixed 50/50 so all you do is pour it in , no need to add water. also make sure your water pump is workin good and that you radiator fins arent clooged up with dirt. good luck.