1999 kx125 mods

[kx125FL99]

i recently purchased a 1999 KX125 because it is much lighter and less tiring than my 1994 RM250. i noticed the KX125 is not much slower than my RM250 and the KX125 is much better on whoops. i want to make my KX125 as fast as i can so what are some good mods to buy? i am thinking of getting a boyesen water pump cover and a renthal rear sprocket. what size sprocket do you recommend or do you recommend a front sprocket? has anyone tried the boysen waterpump cover? what are some other mods that are good for a kx125 any sugestions are helpful.

 

[kx125FL99]

it already has a fmf pipe and silencer on it

 

[CaptainObvious]

Try the Delta Force II reeds and cage. That, with your pipe (along with proper jetting) will get you some bottom end without any loss up top. Also, make sure your top end is within spec. The 125's just don't last as long as the 250 you are used to riding.

The water pump and cover is really for they guy looking for that last 1/8 of a hp. It's a last mod, not a first.

 

[kx125FL99]

i recently bought a 99 kx125 which is a bit slower than the 94 rm250 i am used to riding. i have a fmf pipe and silencer on it already and the piston is being replaced right now. i am looking for mods to make this bike faster than my old 250 what parts do you suggest? i was reading about boyesen water pump covers, has anyone tried these? what size rear sprocket do you guys recommend or do you recommend a front sprocket? i want to make this bike fast! any suggestions are helpful.

 

[blanc]

I would put on the waterpump and cover straight away, anything that improves cooling is a must have. I am about to go 125-250, is there a big difference, are 250s scairy fast? Perhaps have ericc gorr do some motor mods!

 

[rairden]

There are alot of bolt on mods. You could have the cylinder ported, but read up on that before you make a decision. A ported cylinder(I think) could do more for you than all the others combined. But one thing about that is once you get it you cant take it off(its not a bolt on). Read up on that.
And adding teeth to the rear gives you a greater mechanical advantage. I forgot why.

I'm getting ready to go from a '01 YZ250(yes blanc, wicked fast) to a '03 YZ125. I wont be disappointed will I after riding the 250 for a full 7 months. This was my first bike. I love it, but always thought I should've got a 125 first; besides I'll be able to control it better.

 

[marcusgunby]

The porting on the pre 03 kxs wasnt good, eric gorr can make good gains on the KX-i think they were actually overported and can gain power with lowering the ports-check with eric as its been too long a time for my brain to work effectively.