need some help... my r runs great great for a little while then after its been harm for a bit it starts breaking up. tryed a new coil and that didnt work. any one know what it can be?

 

Could be a bunch of things. Are you sure you have a good plug in it? Is it jetted right, maybe a little rich? Did it used to run fine, then start doing this without you making any mods/changes to the quad? Maybe a wire in the wiring harness is bad, but doesn't short out until it gets warm. I had an e-start dirtbike that did that to me in the starter circuit. Once I got it started, I would just unplug the key switch, which bypassed the whole circuit, and kick start it for the rest of the ride. Also, it could be the CDI, which you can't test. The only way to figure that out is to swap in a different CDI.

 

If your jetting is OK, sounds like an electrical problem which the R's seem to have unfortunately, of course, they are getting old!! Check your plug wire, put on a new one if yours is real old. If you can afford it, get the ESR CR250 ignition for the R, I did and it will eliminate those intermittent electrical problems. If you got a buddy with an R, ask to borrow his CDI box and see if that cures your problem.