need mods for a KX100

[Humdinger]

I am a KDX rider and I visit this site often for tech help. I just moved my son up from a TTR 125 to a KX100. He is 11 years old and isnt tall enough for a KDX yet. The 2001 KX100 we bought is bone stock.
It seems to have no bottom end torque and only wants to run wide open. We mostly trail ride with an ocassional trip to the local motorcross track. How would I go about setting up this bike for serious trail ridding.
Pipe, Jetting, reeds, reed spacer, flywheel weight, this bike needs some bottom end.

 

[CO Dan]

Hum,

I'm setting up an 01 KX100 for my daughter (12, 5'6" tall) for trail also. Maybe we can keep in touch about what works.

My daughter has been riding an XR80 for a few years and she's more of a putt-putt rider than a screamer, everything is either too small for her (like the TTR125L) or too heavy or too tall (like a KDX).

Anyways, the mods list I have in mind is...
1) steahly flywheel weight
2) Eric Gorr porting
3) gearing change to let her go slower.

If you look in the women's forum at the CRF150 thread, you'll see some discussion there. Also search (in the KX/YZ forum I think) for "KX100 --> trail" for a thread I started earlier.

Good luck,
Dan

I'll be interested in seeing what others have to say.

 

[LocoCD]

My son raced a decked out TTR125 for a while and we made th switch to the KX 100 last winter. There is no comparison. As modified it is an exceptional trail/HS/Enduro bike with significant low end. We did and learned the following:
1) ST pipe and turbine core muffler
2) Boyeson Pro Series dual stage reeds worked well, however, the bike runs much quicker with carbon tech low tension reeds
3) Jetting - dropped 2 main jet sizes (I think we are running a 132 main now - still blows spooge but runs very crisp)
4) 32:1 synthetic 2-stroke oil (we are running Motul) with VP C-12 (I know all the arguments about the pros and cons of race gas, compression, etc. - but it simply runs cleaner with the VP)
5) Triple clamp, fat bars and brush guards
6) Twin Air air filter with NoToil
7) 428 chain conversion with an extra tooth on the rear - we add an extra tooth on the fronth for desert riding
8) Full skid plate (not the little MX glide plate)
9) IMS fuel tank
10) Excel rims - these were replacements for the stock rims that got square in the rocks
11) Michelin tires

We change the oil after every 2 rides, clean the air filter after every ride and the bike is very reliable. BTW, with these mods there is no need for a flywheel weight.

I'll post a photo if you want...

Have fun!

 

[XR100rRida]

yea i wanna see a photo. also what is the weather around you. here in michigan it's like low 40's. what would you suggest for jetting for these temps. i moved my jet needle on position leaner. and i followed 2 plugs since. what should i do so i don't follow so many plugs?

 

[Glitch]

Going leaner on the needle is the opposite of what you want to do XR100rRida. When its colder out, there is more air molecules per volume than there was when it was warmer out. So therefore your jettin will become leaner because there is 'more' air being sucked in. So you would want to turn your airscrew in some, lower the clip on the needle, and maybe go up a main jet.

 

[XR100rRida]

my spark plugs are still dark and wet though. so i should order a size large on the main jet. turn the air screw in till i get the fastest idle and lower the clip back to were it was?

 

[Fred T]

Originally posted by XR100rRida
my spark plugs are still dark and wet though. so i should order a size large on the main jet. turn the air screw in till i get the fastest idle and lower the clip back to were it was?

No. It appears that your bike comes rich stock. Jetting is a process where you start with getting the main jet right and then work your way down to the pilot. I suggested you try the needle adjustment so you would get a quick fix and see if you need to go leaner -which appears to be the case as it got better once you went and dropped the needle (raised the clip). If you know how to do a plug chop you can try that, get the bike warmed up with a fresh spark plug then ride it WFO-hold the throttle wide open for 20 -30 seconds and kill the motor while it's still WFO, close the throttle and read the plug. If it still looks rich lean it one size on the main jet. Leave the needle where it is and ride it to see if it still fouls plugs. If it does then you may need to go even one smaller on the main. Remember when asking someone else about jetting air temp is only one thing to consider, altitude is another important factor. Here in MI we are pretty much at 1200 FT most of the time.

My guess is that once you go one smaller on the main, leave the needle where it is and turn the air screw out a bit it will run OK in these temps. When it gets warmer you'll probably need to drop another size on the main, possibly one smaller on the pilot and turn the A/S out more. If you get to 2 1/2 turns out on the A/S then you need to go smaller on the pilot jet.


HEY -BTW do you still have the stock air filter for the XR 100? Seems that the Uni is not fitting well so maybe an adapter is still on the stocker?

Good luck, PM me if you want to.

 

[XR100rRida]

i can't pm you. something about the way they changed the site due to expenxex. I don't have the stock air filter :(. I got a new one because when i removed it to clean it i got it caught and there was a tear in it, that's why i got the UNI. Ok thanx for the info. feel free to e-mail me or my dad. Mine is [email protected] and my dads is [email protected]

 

[Racer#213]

ok i changed my name fred. no longer xr100rider cuz i no longer have an xr100 thanx to you :yeehaw: just thought i'd let you know.

 

[Fred T]

Originally posted by Glitch
Going leaner on the needle is the opposite of what you want to do XR100rRida. When its colder out, there is more air molecules per volume than there was when it was warmer out. So therefore your jettin will become leaner because there is 'more' air being sucked in. So you would want to turn your airscrew in some, lower the clip on the needle, and maybe go up a main jet.

He's fouling plugs now in the colder weather, getting the bike even richer is not going to solve his problem. I had him move the needle to see if the bike was rich - it would either run better or no change. It ran better leaner, so he's gotta rejet the thing. I have no idea if Kawie chokes them off at the air cleaner like they do the KDX's but it's clearly getting too much fuel right now. We're trying to help him. teach him jetting and not confuse him. I'm working him through it via e mail. 1 step at a time. Feed a man a fish he eats foir a day, teach a man toi fish and he gets sick of eating fish but he's not hungry.