KTM 125 exc

[steveB]

Hi

I’ve recently bought a ’99 KTM 125exc after an eight-year absence from dirtbikes. The bike has been raced professionally and last competed in the ISDE in Granada i.e 2000m above sea level. Am I right in believing it would have been jetted leaner to compensate for this high altitude? It’s currently using a 180 main, 42 pilot, has the clip raised one notch on the needle and the air-screw set to 1.5 turns. My manual suggests a 190 main and 48 pilot but from what I’ve read KTMs seem to be jetted rich from the factory.

I live in Scotland with the current average temperature at about 10-12 degrees (if we’re lucky) and I’m riding not much above sea level in tight muddy woods. From idle to quarter throttle the bike is quite erratic and splutters badly with the mid range only slightly better (almost seems like it misfires at times). Half to full throttle tends to be fine most of the time but occasionally bogs (too rich?) going into the powerband. I’ve tried a 45 pilot and putting the needle clip back in the middle position but to no avail.

I realise that all bikes/ conditions are different but any jetting advice would be cool as the bike is very hard work just now in these tight slower areas. I also read somewhere that bunged up exhaust valves can produce symptoms similar to poor low end jetting. Can I check/ clean these without removing the barrel? I apologise in advance for my lack of technical knowledge and any advice would be appreciated – is there any other possible non-jetting problems I should check for?

Cheers
Steve.


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[jeb]

We had to lean our 98 125 EXC out quite a bit to get it running clean. However, I don't know what the current settings are as it's been quite a while since I've torn into it. I think I went two step leaner on everything (clip and both jets). The #7 slide could help, too, but I never tried that.

KTM 2 strokes are always jetted fat from the factory. There's not a lot of jetting specs on the 125 EXC that I've ever seen, though.

I could be persuaded to tear the carb down for a look see but it'd involve hoisting a dark lager or two, at least in spirit.

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John Brunsgaard - JEB
01 KTM 400 EXC, 99 KTM 250 EXC, 99 KTM 200 EXC, 98 KTM 125 EXC, 98 KTM 380 MXC (gone), 96 KDX 200

 

[marcusgunby]

I suspect you will need to go to the top notch on the needle to get it to run clean.

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[BSer]

I have a 99' 125EXC also. It's been awhile since I've played with it but I think it's a 45 pilot, 1 to 2 clips leaner on the needle, and a 180 to 185 main jet. I used the leaner settings for a whole year of woods riding (180 and 2 clips leaner) but went back to the 185 and 1 clip leaner when I started riding more wide-open runs and sandy areas. I didn't notice much difference.
I tried to run a #7 slide with the 45 pilot but the bike started hard and idled erratically. I think I tried the 42 pilot with the #7 slide also. Anyway, I never felt comfortable with the #7 slide so I ditched it and went back to the #6.
I ride 1000' elevation (300m) in temperatures from 60 to 85 degrees F (?C). The bike blubbers a little on the bottom end yet but it isn't enough for me to worry about, even in the tighest of woods. With a 45 pilot and 1 notch leaner on the needle you should be in the ballpark.

Hope this helps.

 

[robj]

Steve, it might also be worth calling Eurotech. I don't have the number to hand but I know it's close to Carlisle, Cumbria. They've been prepping Exc's for years.

 

[steveB]

Wahey!

Went out yesterday as it was a lovely warm afternoon (rare in Scotland) and the bike was so crisp. I'd stuck in a new plug, air filter and a 42 pilot (It was actually a 45 that was in before) and this in combination with the change in climate made the bike run really well. At last I can concentrate on getting my riding skills up to scratch after 8 years...

final jetting:
180 main
42 pilot
needle one clip leaner

Anyway thanks for the replies!

Steve.