250R is cutting out. Any suggestions would be appreciated, sometimes the obvious is overlooked when you've been trying to troubleshoot for hours. I've tried jetting it for lean and rich. We've replaced the stator coil, ignition coil and the pick-up coil and still cutting out on top end. Have tried two seperate carbs on it. I have a race tomorrow and desperately need any suggestions that you can offer.

 

try a spark plug.. but i would check the CDI box

 

Just got through trying a CDI box which we know is good from another 250R that races with us. Didn't help. We've tried 3 different spark plugs with no improvement. Am now trying some adjustment to the new boysen reeds put on last night. Thanks for the suggestions as we are completely stumped right now.

 

Are you getting "blow back" through the carb? That would indicate your reeds are not sealing at high RPM's.
How about have you looked at the possibility of your crank seals going out? The crankcase has a lot more pressure on it at high RPM's, and if the seals are weak, it will cause the scenario you are describing.

 

air leaks anywhere? around carb boot? air boot?
stator cover? clutch cover? anywhere? spray it all w/ WD40 while its running and listen for engine speeding up that would indicate an air leak..

 

is your compression good?

 

Try this , gap the spark plug to .020" and try it.

 

i guess you checked that there is good spark (no loos wires that could not be connected).