i've just seized the engine in my 97 kdx200 and am about to rebuild it. its currently standard with a pro-circuit exhaust (full). i've been thinking about adding a boyesen rad valve. i haven't ridden in around 8 years but used to race a rm125 and remember it being alot faster. basically are there any mods i can do keeping it simple incorporating kx parts eg. exhaust valve, etc to make this thing go more like a kx?
Porting
RB carb divider plate (bored to 36mm)
pipe
silencer (loud really isn't faster though)
reeds
torque ring
airbox cover
over bore
head mod
jetting (bigger deal then you might think)
gearing (its a trail bike so its a wide ratio, lower it for more snap)
It makes the headpipe longer which lowers the power band a little. Say you are "one pipe" from 6000-9000 rpm, the torque ring will move that to something like 5700-8700 rpm. Doesn't give you any more power, just adjusts where it is at.