Wow! Top end inspection

[Matt90GT]

Well today I finally got time to tear into the top end of the KDX250. Nothing wrong, just it is time to do a top end. Compression was down to 140, limit is 220-145. Bike ran good, seemed a little flat up top. Tons of low end.

So get everything off. KIPS are not seized which is good, but the the amount of carbon on the KIPS and center exhaust valve was unreal! I could not believe the system still worked! I thought at first the center exhaust valve was toast cause it looked like a scratch about 1/4" deep in it. After about 4 hours of soaking in solvent, it is carbon build up! wow!

Anyone know how much the left and right KIPS valve go for at the dealer roughly? A few teeth are not looking good and the other one has some plating that is coming off the top shaft. Figure I should replace both while I am in there.

Anyhow, figured I have a B piston in the bike. Just waiting for some new tools I ordered to come in to measure what I need. Found out the cylinder is lightly ported. Opened up a bit and smoothed the corners mostly. I got a VforceII for the bike and then get the dents out of the pipe and I should really find some serious power in the motor!

 

[jaguar]

I don't know how much dealers mark up the price but if you buy from bikebandit.com then the cost is around $38 each.

 

[Matt90GT]

That sounds liveable at least.

 

[woodsy]

Hi Matt: I know your bikes jetting and stuff but what kinda oil have you been running and at what ratio?
Woodsy

 

[Matt90GT]

Since i have gotten the bike I put the Amsoil series 2000 @ the recommended 50:1 ratio.

I think most of this carbon was from the previous owner not doing a top end rebuild last year and the jetting being off for so long. Time will tell next year for sure to see if my theory is correct.

 

[Matt90GT]

Forgot to add that when I got the bike it was 90% JB weld, 10% kawasaki. The engine and mod were good with the plastic and frame. Rear suspension and bearings were not.

But inspecting the clutch, found that 2 of the 6 springs were not installed. Got to love that!

 

[canyncarvr]

WoW. Six springs?

The 'I'll only use four...' idea; maybe that was his idea of a 200/220 'upgrade'??;)

Enjoy your new bike!

 

[dirt bike dave]

Matt - I think you are right that most of the carbon was due to the previous owner's rich jetting. With the jetting cleaned up, my 250 never had a problem with excess carbon or stripping kips gears.

If you install new kips valves, check to see if there is a smooth transition to the main exhaust port when the valve is open all the way. On mine and my friends, the floor of the open valve was at least 2mm higher than the floor of the exhuast port (on the pipe side of the valve, not the piston side). We removed some material from the valves to make a smooth transition to the exhaust port. This had no detrimental effect on low or mid range power, but added some top end.

 

[Matt90GT]

Thanks for the tip Dave!