125-200cc WR 125 bogs/sputters at full throttle

Hey, I just bought a 1999 WR 125 and it ran ok for a while but after about ten minutes it started to bog at full throttle. So I put a new plug in and it ran ok for about ten minutes and then the same thing happens. It runs ok every time I put a new plug in, but after I ride it for a while it starts to bog at high revs then about two minutes later it bogs at low revs and finaly dies and I can't start it. If you have any suggestion, let me know. I think it is an ignition problem. Can I put a cr125 ignition coil on a wr125?

Is the plug fuel fouled when you take it out? If so main jet is too rich, most likely.

Either that or the fuel valve / needle and seat are leaking.