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Need advice with a ´02 400 exc

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Hi guys,

I have a 2002 400 exc.

I got it at the end of last year for pretty cheap, but it was poorly taken care of.

When i received it it had been used without an air filter... I had the motor opened up and cleaned .. we also did a series of oil changes.

The mechanic said that the piston and cylinder looked good, it had new rings, and that he hadn´t found any play on the rod or valves.

As a background i live in Mazatlan Mexico and there aren´t many trustworthy shops or acknoledged mechanics around. This guy it´s the most honest of them all but he doesnt care about piston and rings clearence or about valves

Since i got the bike the kickstart offered little resistance when kicked as ifit lacked compression, and it was kind of dificult to start it that way, but it fired up on the 1st try with the electric start. So i didn´t worry about it much.

Later on this changed and kickstarting it was possible.

The mech said he had checked the compression and that it was ok, also the bike sounded and responded pretty well.

Since I got it it makes a clanking noise, i had read in several forums that it was due to the decomprenssion system on the bike and it seems that way because if you pull the decom lever while the bike you are on the throttle with the bike running the clanking stops. It also minors down at higher revs.

But all my friends have me worried ´cause they say that it must be the rod the reaon of that noise, that i have to take care of it soon before the bike goes KaTooM.

Anyway i had been riding the bike fine,starting it easily with either the kickstart or the button, until a couple of weeks ago where i have been experimenting problems starting the bike the 1st time in the morning.

You can kick it al you want or empty the battery from using the electri start ut it just wont fire up.

After that 1st start, the bike starts right up either way with the button or the kickstart. With some rare exceptions when the bike suddenly dies and i struggle to get it fired it up the 2nd time.

I had to recurr to bumpstarting it, but even that way it doesnt start on the first try.

At first i tought it was the carb... flooded with too much gas (maybe the lever that stops the gas from flowing to the carb *i forgot its name* doesnt work well.)

But lately i have been noticing that if i try and find the compression sweetspot by slowly kicking the kickstar while using the decom lever it can be fired up after a couple of tries. (That´s like 10 tries or so)

I have gone to a diferent mech and he said it might be the carb float needlee but he said he wasn´t sure.

I am worried at my friend´s diagnosis that the clanking noise i described earlier migth be the crank and that the lack of resistance of the kickstart means it´s time for a complete top and bottom end rebuilt.

Other say that i need to swap the valves.

I dont know much of 4 strokes and even less about the ktm´s exc, only what i have read about them online.

But i find irt strange that it only experiences issues on the 1st start up.

The thing is that neither mechaninc is 100% sure about what´s wrong.. and i dont want to change stuff that doesnt need to be changed since it is a beater bike. I just bought a mint conditions 07 kx250 :smirk:.

Sorry for the long post i apreciate any advice on this matter.

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Adjust the valves,there is a stickey at the top of the page that has a video on how to do it. Good luck.


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The crank primary gear aluminum 27mm left hand thread nut is probably loose as they all loosened up.

Lock the crank with the locking bolt and clean the threads on the crank and use a little red loktite on the threads only.

Tighten to 150 newton meters. Left hand thread.

Ohm check the stator. Connect an ohm meter to the two terminals in the blue female connector coming up from the ignition area.

New will be 15 ohms and partially shorted will be 13 or less. When hot they short even more internally and the non starting hot is the symptom of a bad stator.

They all died until 06 production and after. Date is on the stator. Letter and number. Number is the year.

I have good used here mounted in used covers and can ship to you. Or new stators if you prefer either unmounted or mounted in a used cover ready to install.

Pilot jets plug in the carb and you need a 48 pilot in the 00-02 carbs. $4 part.


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