What other modifications do I need done to my klx 250s to accept a 351 bore kit?

 

none,,,,,,,,
Although an aftermarket muffler helps the 351 reach its fullest potential. There are other mods you can do but I think they only return marginal gains.

351 and FMF Q4,

Dan

 

A rejet

 

Tom Edison 351nd his 09. It has a jetted stock carb and a K&N. Seems fine. If I had a stocker the 351 would be the first thing I would do.

 

so what jets should i get? and does anyone have a idea how much improvement a new exhaust and header would make on top of the 351?
also would i need different jets if i have or do not have the new muffler and header?

 

Frampton, have you read much of the post history on the 351 install and associated jetting? While it may take awhile to read through this info, if you're fixing to spend this much money and time doing the job, I think you'll find it worth your while. You're asking the most basic questions which are covered many times here already.

 

Replace the clutch springs before the oem springs let it slip rendering your clutch plates useless. Barnett offers some that work well.

Power increase with the big bore kit quickly shows how the tension of the stock springs are inadequate in the upper gears (slippage)

 

thanks for your post TNC but i have read alot its just that i have heard different kits and most of them for bikes that have a aftermarket muffler aswell. the main reason for my posting is to learn exactly what jets i can choose and if a new muffler and header will actually help much

thanks!

ps: i am at sea level

 

Impossible without knowing elevation

 

Sea level sorry