Ok, I just bought this 250r. The reeds were bad so i replaced them with the Bosyen Rad Valve, it helped out some, but I think I still have a problem. So, it's on to the jetting and sprockets, my front one is 12 tooth my rear is 38 tooth. Tire size is 20 X 10 X 9, I was thinking of changing the front to a 15 or so to get better low end performance, is this the correct way of thinking? How does it work, smaller sprocket up front higher or lower topend? For the rear, larger means more low end power correct??? With the jetting I can tell it's running rich buy the plug and Boysen said I should run a 142 main jet. Right now it has a 150 jet in it. Also, I did a compression test and I got a reading of 151psi, is this good or bad?

 

the smaller the front sproket the better the low end ...one tooth on the front =3 in the rear ....151 comp is low ...bore it and rering it and have someone who knows two stokes jet it for you ......should bring comp upto 170-180 range...good luck shave the head to raise it up higher!!

 

I'd disagree about 151#'s of compression being low. I'd look at a rebuild at around 130 psi, definately at 120 on a 250R. Stock compression is only around 165 psi.

Sounds like you're headed in the right direction in reading your plugs. RAD Valves typically require a size or two leaner from a stock set-up. What pipe & air filter, mix ratio, and elevation are you running at?

 

My pipe is a Bill's the air box is stock with a K&N air filter. As for elevation I don't have a clue. Also redid the compression test and came up with 159 to 160 on a cold engine. Mixing the fuel at 24:1 Thanks for the help