Vintage Dirt Bike Q & A

I have a 1976 mt 250 with running problems. It will only rev up to 6500 rpm and is oiling the plug badly, it also seems to use a lot of fuel. I rebuilt the motor last year with new crank seals and piston rings, the bore was checked and was within wear tolerances. The air filter is ok and the exhaust has been changed for a DG pipe, i am using a NGK BR6ES spark plug at the moment.
Any help would be great. thanks marc.

I have been in a battle with my 1976 MT 250 with almost identical symptoms. I have finally gotten a hold of the problem when I found a mechanic that discovered the carb was the problem. He replaced the slide needle with another from a spare carb that I had and the problem was cured. Mine too fouled plugs, consumed lots of fuel, and smoked bad. I would suggest rebuilding the carb, replacing all that you can find with new or good used parts.
Good luck, and let me know how things turn out.