KT100 dry clutch

I have a KT100 with a centrifugal dry clutch. I’m having issues with the way my clutch is held on the drive shaft as the nut would originally tighten too far and the clutch would be pressed together all the time and not slip. I have since fixed that issue but now the nut seems to come loose. I’m interested to see how others have theirs set up. I can post pictures soon.

Also my brakes lines split very quickly at the rear intersection where the lines seperate to left and right calipre. They appear to just be pushed inside a fitting with no retention to hold them in. Any alternatives.

Lastly, I was having dramas getting it to idle. Once it was started, if I didn’t leave it on throttle it would die out. Can I tune the carby to aid idling or is this how they are?

Welcome to KP. It’s been a while since I have struggled with an Yamaha but I think you have an issue with the inner spacer if the clutch won’t spin free while the starter nut is tight. To keep the starter nut tight I usually used blue loctite every time I reinstalled it. If you have previously used blue loctite sometime you have to chase the threads to get rid of old excess threadlocker.

As for your brakes, I would need to see what you have. some have a banjo fitting others thread into the housing and have a compression type fitting.

As for the carb settings, there are different ways to address your situation, however, 2 stroke motors in general are not great at sitting idling. They are set to run on the track not idle in the pits. Some guys will lean the low needle down and then when running open up the needle as needed. Some other factors could be the fulcrum height, pop-off pressure, condition of the diaphragm, oil fuel mix to name a few.

I’m not familiar with many of the terms you just listed hahah. In terms of screwing down the low needle on the carb, it is currently set on 1.5 turns. Would I need to screw it more to 2.5 for example or less to 0.5 to potentially allow it to idle.

I currently don’t race it. Just drift it on a track out of town and often need to stop and start but by the time I start it, it’s dying before I can get in and when I stop it won’t idle for long before cutting oit

It shouldn’t idle, it’s built to run at high revs so they simply don’t idle.

2.25 turns open in the low speed needle (big T shaped one) and 1/8th open in the high speed needle (little L shaped one) should be a decent starting point in carb settings for actual running. But it simply isn’t going to idle and also be dialed for high revs, so you’ll have to keep some throttle on to keep it running.

A pic of the braking issue would probably explain more.

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This lead off to the left caliper came out of the brass fitting and I lost all brake fluid. They are just push fittings.

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Now thats a hard working Kart out there man !!

The T you have pictured are all compression fittings.

ON the hose should be a ferrule, the nut should be on the outside end and the fitting in the inside. When you tighten the nut to the fitting they are compressed together. You might just need the ferrule, but tf the line is damaged you may need a line too. You might be abe to find what you need at a good auto parts store. This is what the parts would look like:
1955C: Compression fitting repair kit for 3.5mm OD line - FPS West - French  Parts Service

as for the carb settings, think of the needles as a water faucet. Turning the needs clockwise will restrict flow, unscrewing or counterclockwise would open flow.

It would appear you are running on dirt. Make sure you are running an air cleaner filter and maybe even a double filter.

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The nut holding the clutch onto the axle has just come off again while the hart was running which let the drive sprocket come off the centrifugal clutch which let the wings of the clutch expand and smash into the motor. Why won’t my clutch stay on?

The spacer that fits on to the motor shaft is directional. The concave side faces the engine and the flat side faces the clutch. It is a must to have the fixation tool specific to your clutch. Never clamp the opposite side of the crankshaft while tightening the clutch. Lap the clutch onto the crankshaft end then clean off any lapping compound residue. Use a little red Loctite on the starter nut and torque to somewhere between 25 and 35 foot pounds.

Interesting x 2. I’ve not familiar with either the double starter nuts or that three pedal device which I’m assuming is a rotating clutch guard.

I’ve never seen a clutch like this before.


As others are pointing out, this is not a common racing clutch. The last time I ran a Yamaha it was using a Patriot clutch.

While there are other brands, most operate the same.
I don’t recall this clutch even being offered for sale so I wonder if its for another use.

The clutch in the photo is after it exploded. Usually it’s a circle contained inside the sprocket clutch peice and operates as a normal centifugal clutch. But because the nut came completely off and the sprocket clutch piece came off the clutch plate, and the engine was then able to freerev because it was no longer driving the wheels, and the centrifugal force made it spread open and not stop.

I’ve attached a photo of what the clutch normally looks like. This is a photo of the back.

That must have been a violent fail…Just looking at the 2 nuts , I assume that to be a jam nut? What is your procedure for assembly?

Put centrifugal clutch friction wheel on first. Tighten onto taper lock. Slide sprocket clutch piece on with chain. Thread brass bush on until it bottoms out, pressing the clutch together. Thread locknut into brash bush until it touches drive shaft. Unthread brass bush back onto the locknut to give clutch about 1 mm of clearance so it can slip.

Okay clutch has been replaced and stays on now but this one is a bit old and is missing some friction pads so it doesn’t want to grab too well. Will probably need to buy a new one.

The bigger issue is that occasionally as I come off power for a short period, it will die even if I’m moving at decent speed. I understand they don’t idle well but I would imagine it could coast alright?

Probably has to do with your clutch engagement, which seems to be lacking due to the old plates. It may not be engaging as well as it should, allowing the engine speed to drop too much to where it dies.

My thoughts exactly. I’m going direct drive for now as a new clutch is 350$ AUD.

Unless anyone knows where I can get a replacement for just the friction part of the clutch. Mine is an italsport