I've had a problem with my 86 250r sputtering and not having any pull when accelerating since I've owned it. I thought it was the piston worn out so I put on a 310 kit and it still sputters. I measured the voltage and it is only reading 11.5 volts. It should be 13.5-14.5 volts and the book tells me to check the ac regulator. For some reason the ac regulator won't give me a reading. Is the low voltage reading caused by the ac regulator or is it caused by the stator? The stator gave me a good resistance reading of 115, which is in the middle of the specs. Also, can this be the cause of my midrange and topend sputter??

 

From your description, it sounds like the main jet on your carb is not right. Symtoms indicate it's to rich. Did you re-jet the carb after installing the 310 Kit ? It sounds like jetting was off before the "310" was installed and jetting is required after any changes to the motor. Not to mention changes air temperature and elevation.
Another thing to check is sparkplug gap. Out of the box, most plugs are gapped too wide and this will cause loss of power at top end.

Hope this helps,
Dave

 

if i were u id check the stator even if it got a good reading. take some sos pads and clean it right up and youl notic a big diffrence

dfox is right about the jetting and the spark plug.

what size main jet are u running?

.........by the way if you have never took a main jet out uncrew the little bold on the right side and left of the carb where the rubber boots hook onto the carb. (just loosen them) then turn the carb, so the bottom is facing u, and so the carb is almost side ways.(slow and easy) then take the float bowl screw off (big screw on the bottom) after you take that off u will see the main jet right there. take a small socket and unsrew it and look at the # grooved on the side of it. (thats the size) this is very easy after u do it once.( DO NOT FORGET TO SHUT YOUR GAS OFF!!!!!) gas will drain out for like a few seconds but thats because theres gas in there.

also when you regap the spark plug gap it at 20 or 18