'97 KTM 250 EXC External Flywheel Weight Removal

Smokin Joe

Sponsoring Member
Apr 21, 2000
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#1
The '97 250 EXC that I have works well in the low end but doesn't like to accelerate out of it however. It pulls and chugs well there but just won't accelerate without a lot of clucthin' and I mean A LOT! I've got Boyeson 2 stage reeds, reed spacer (previous owner) Gnarley Pipe, TC-I SA and have it jetted pretty well with a Honda 1368N dual taper, #7 slide, 42 pilot and 185 main.

I'm suspecting the external flywheel weight and am dedating whether to try and remove it. Motorcycle Online has an old "Trail Rider" test where they mention removing it. In the Trail Rider test they quote KTM's Tom Moen as explaining that the same weight was used for all EXC ignitions so they used a weight for the worst case scenario which would be controlling the 360. I think Dirt Rider mag also had a similar comment when they tested the 300 MXC. Shops I've talked to have recommended against removal but the way I see it is that as long as I don't bugger it up I can always reinstall. Do any of you long time KTM'ers have any experience with this? I think the '97 was the first year for the Kokusan ignition and maybe they went overboard with too much flywheel weight. Even without the external weight the lighting coils and the milder advance curve should keep it from being "wheel spin crazy".

Thanks for ya'lls input,

Joe
 

KTMMIKE

Lifetime Sponsor
Apr 27, 2000
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#2
Joe,

I had a '97 250EXC & I had a machinist remove some of the weight. He just shaved some of the O.D. off. I don't remember the exact amount though. It worked real well. I did this on my '98 also. In '99 the 250s had lighter crank & the stock weight worked fine stock.

Feel free to call if you have any ?s
 

Smokin Joe

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Apr 21, 2000
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#3
IT'S AWESOME!

Did it the crude way by drillin out the bolt heads; no going back either since I went a little overboard with the drill and augered out a little around the bolt holes on the flywheel. fortunately, it runs so well now, I'd never consider putting the weight back on. ;) Then after a few light taps with a blunt center punch through the holes, the flywheel came right off.

Boy, what a difference! It pulls nice and strong right off idle without having to abuse the clutch. Much easier to get it on the pipe in the deep sand also. The good thing is that it still maintains good controllability. No problems with excessive wheelspin, just good linear acceleration. I will need to slightly re-calibrate my right wrist for the improved low-end responsiveness but that is a happy trade off for the sleepy low end acceleration that it used to have. Now if I can just fix this stupid overheating problem!:think

Joe
 
Oct 25, 2013
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#4
he guys i have a 97 ktm 250 exc and just recently removed my flywheel weight as well i was wondering if after you guys removed your weight if you had any idle issues? after i took mine off and got everything put back together my bike started to idle super high was curious if you ran into this same thing when doing yours and if removing the weight is what caused it or if i have somethin else going on with my bike now for some reason
thank for your time hope you get back to me
 
Oct 6, 2014
1
0
#5
The '97 250 EXC that I have works well in the low end but doesn't like to accelerate out of it however. It pulls and chugs well there but just won't accelerate without a lot of clucthin' and I mean A LOT! I've got Boyeson 2 stage reeds, reed spacer (previous owner) Gnarley Pipe, TC-I SA and have it jetted pretty well with a Honda 1368N dual taper, #7 slide, 42 pilot and 185 main.

I'm suspecting the external flywheel weight and am dedating whether to try and remove it. Motorcycle Onlinehas an old "Trail Rider" test where they mention removing it. In the Trail Rider test they quote KTM's Tom Moen as explaining that the same weight was used for all EXC ignitions so they used a weight for the worst case scenario which would be controlling the 360. I think Dirt Rider mag also had a similar comment when they tested the 300 MXC. Shops I've talked to have recommended against removal but the way I see it is that as long as I don't bugger it up I can always reinstall. Do any of you long time KTM'ers have any experience with this? I think the '97 was the first year for the Kokusan ignition and maybe they went overboard with too much flywheel weight. Even without the external weight the lighting coils and the milder advance curve should keep it from being "wheel spin crazy".

Thanks for ya'lls input,
 
Jan 2, 2002
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#6
I did exactly the opposite. I just installed the 1.45lb S3 flywheel weight on my 97 GasGas EC250. Previous owner took out the lighting coil and whatever was on the end of the flywheel. Now I can lug and chug like a tractor :THUMB:
 

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