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KX100 pipe test... 85 too

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Well, just for FYI in my own experiments, My son had a 2006 KX100 and since I had some parts to play with, I did my own R&D with him and his friend test riding. Both are very qualified riders.

We tested the following parts in many different configurations over a period of 2 consecutive days. So the Weather was about the same. 82-85*, 76% humidity. Fuel was pump 93 w/ Amsoil dominator 44:1:

Pipes = Pro Circuit, Bills pipe, FMF pipe fatty gold.

Silencers = FMF power core 2, PC T304 shorty.

Reeds = Stock box with carbon fiber reeds, Vforce3 reed box.

A given is the reeds. They are a definite upgrade. If the track is nasty, muddy and slick. I will put the stock reed box back on to limit the power to keep from overpowering, thus keeping more manageable power to the ground. Jet accordingly.

After testing all the pipes systems with each configuration, we found that a Bills pipe with the PC t-304 shorty made the best power, wide powerband and instant throttle response. Even more so with the Vforce reeds installed.

But the following was reported by my son and his friend as they tested the bike.

Configuration = Pipe/Silencer/reeds.

Test 1. Stock/PC shorty/stock…no difference from stock, just louder

Test 2. Stock/PCshorty/vforce… Snappy response rips out of turns, top end suffered, had to jet.

Test 3. PC/PC/vforce…No lowend, mid pulled hard, topend ripped right into overev.

Test 4. FMF/FMF/Vforce…Good lowend, wicked midrange pulled up to top then fell off. Jetting up main helped a lot.

Test 5. FMF/PCshorty/Vforce…lost power, tried jetting, no use, quit config test

Test 6. Bills/FMF/Vforce… Pulled hard through entire band after jetting. Lagged slightly on lowend but quickly got into powerband. Didn’t snap up to overev but had no problem getting there. After 2 days riding, both boys laptimes were 2 sec faster with this setup.

Test 7. Bills/PCshorty/Vforce… Same as previous but got it overev quicker. Better topend

Jetting = Since we are at a low 700' asl, we really haven't had to do any major jetting. We started with the pilot down 1 and the main down 2. After vforce reeds, Stock pilot was needed, main stayed down 1 on test 2. All others, stock pilot and main would go up no more than 3 sizes up. Needle clip wasn’t changed. Air screw ended up at 1 ¾ turns.

This may not be the same for an 85 but will be close. Your location will also have variations.

*WARNING*

Advisable to immediately upgrade your drive to a 428 chain and sprockets. The stock 420 will not hold for long. My son broke 3 chains in 2 weeks. They were all stress breaks. Even the strongest 420 made were stretching every couple of laps. Finally we upgraded to 428 and no problems in 3 races and practice riding everyday.

Hope this helps someone.

Edited by SAPPERS

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You should test this with the SST pipe offer by FMF. It claims to add a lot more midrange to overrev, but I'm not sure since I have a stock KX100. I know this isn't written in your tests but did you ever try Bills/FMF/stock or Bills/PCshorty/stock?

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during these tests that was all I could get done in the 2 days. All the pipes were borrowed from friends. The reeds were ours.

Bedsides, after messing with that damn bike for 2 days straight, I had enough.

As far as the bills/PC/stock. We ran that setup on the stroker. The vforce made it very tough to jet with weather changes. It had a much higher compression ratio so it was very finicky. The stock reeds mellowed it out a bit so I didn't have to do as many changes.

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What sprockets are you running for that 428 chain.I hear there are only 2 manufactures now????

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The front was a JT 555-xx. The rear was last of the Renthals. I found a few on ebay and bought them all.

PBI, JT, sprocket specialists all make them. Vortex, Sidewinder and Ironman will make them on request. I've emailed them all and they have no problem cutting a rear for you. The fronts you're pretty much stuck with the first 3.

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No. we did this about 2 1/2 years ago when we first got the bike. This was before 5 topends, 3 bottom ends, 3 suspensions, 103 stroker and 112 supermini build. Oh yea, the white plastic transformation. I'm kinda happy that bike is gone. But this new/used kx125 is killing me. $$$ :thumbsup::ride:

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No. we did this about 2 1/2 years ago when we first got the bike. This was before 5 topends, 3 bottom ends, 3 suspensions, 103 stroker and 112 supermini build. Oh yea, the white plastic transformation. I'm kinda happy that bike is gone. But this new/used kx125 is killing me. $$$ :thumbsup::ride:
:lol: With all the time invested in Sappers Jr's bike, do you ever find time to do any riding of your own? :lol:

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:lol: With all the time invested in Sappers Jr's bike, do you ever find time to do any riding of your own? :lol:

Yep, between work, the wifes hotrod, his bike, the daughters and other peoples bikes, I get to make about 3 laps a week.:ride:

The good part is, I don't have to rebuild mine too often. Since I just got my KX250 last year, thinking I won't need a topend for another 3 years.:thumbsup:

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well, you know what they say about OPINIONS. Truthfully, it's what you like vs. what works for you and where you're located and what type of riding you do. Just based on the tracks we rode at and what the weather was going to be, I knew exactly what setup he needed. There were a few times where I would swap the stocker back on for more bottom end...till we did the 103 stroker. Then there was no need for pipe change.

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