04 kfx250f

[hauser2169]

hey all, i got a 2004 250 f and doing a top end rebuild.. im wanting to go with a high comp piston. i want to keep it at the stock bore. also while its torn apart should i put a new timing chain in it... also anything else i should look into getting for it... what are the best valves . im not great at shimming them so i might take the head to a local dealer...
thanks in advance

 

[bwood]

Whats your riding level ??? (beginner, amatuer, pro). If your not just riding the heck out of it, racing, or making money with your bike, go with stock type components. Keep the compression the same and use stock valves. Higher compression may force the use of race gas and stainless aftermarket valves generally will require new springs, seats, shop to put it all in, etc, etc, $$$$$. Aftermarket Ti valve usually start out twice as much and up over stock. With stock components and regular maintenance, your bike should run well and be more reliable. Use the money from not buying high priced racing parts and maybe do the water pump cover upgrade (I believe this is the same motor used by Suzuki and has the one piece water pump/oil filter cover-if it has not already been changed). Use stock components and maybe add an aftermarket exhaust and a jet kit. You would probably notice more of a differance in usable power and these parts (usually) don't wear out. Something else to concider when trying to improve a bikes performance, it does not only include the engine, suspension, bearing, linkage, brakes and tires all fall in. Look over you bike and see if it could use any of these things. GOOD LUCK, and yes, it wouldn't hurt to replace the timing chain and tensioner. Also check any timing chain guides for excessive wear.

 

[bwood]

im not great at shimming

You might want to get good at it. This is an unfortunate reality of modern/high rev motorcross engines. Although aftermarket valves may hold adjustments longer, they will still need periodic checks and adjustments. Get yourself a good manual. They might be expensive, but the money you could save by doing it yourself (if you think you can) will more than pay for the manual.

 

[_JOE_]

Yes, change the cam chain. The 04 kxf had some valve trian issues, usually attributed to the springs not being able to control the valve well enough at high RPM. Your riding ability(area in thr rev range where you ride) will make the decision on what valve setup to use.


The water pump cover is a good idea as well. That bikes cooling sysytem was less than stellar, so lots of people used the Boyesen high-flow two peice pump and cover.

 

[hauser2169]

i bought a hotcam shim kit.. im just not certain on the correct way to shim. is there a sticky, and yes i have the two piece pump cover as well. but thanks for all the info.. i guess stock it is

 

[Cabot]

If you have a shop Manual, it should explain how to decide on the shim size.

The Equation is A= (B-C) + D
A is the New Shim Thickness
B is the Measured Valve Clearance
C is the Specified Valve Clearance
D is the Old Shim Thickness