KT100 Clutch Weight?

Should weight of a clutch for a KT100 be a consideration? Coming from other forms of racing it would seem this is a critical factor in choosing a clutch as it’s something that bolts directly to the crank.

I started out a couple of years ago and bought a L&T clutch. It works great, I have zero complaints and I have all the tools to service it but never really thought about the weight of these clutches when choosing, and no manufacturer seems to list the weights of them either.

Recently my brother purchased a KT100 that came with a Horstman clutch on it, when evaluating the differences one bit factor came to light which is that the Horstman is smaller in diameter and 90 grams lighter…about a 12% reduction in rotating mass.

L&T 2 disk mini = 728 grams / 25.7oz
Horstman 2 disk = 637 grams / 22.5oz

Is this one of the secrets of karting we just haven’t figured out yet, the clutches all seem to fundamentally work the same once you set stall speed.
Are there other factors in play we’re not thinking about here?

does anyone have the weight of a patriot 2-disk to compare?

Am I crazy here or is it worth switching to a lighter clutch if I’m trying to squeeze every bit of performance out of this thing?


I have wondered the same thing. Odd no one responded to this question. Every little bit makes a difference, but I suspect in this case it may be insignificant.

I don’t know the L&T dimensions, but lets assume the clutch is a 75mm disc.

At the crank shaft,
clutch inertia = 0.728kg * (0.075m)^2 = 0.004095 kg m^2

Reflected inertia of the kart at the cranks shaft given:
Axle gear = 82 teeth
Clutch gear = 10 teeth
360lb kart weight = 163.6kg
5.75” rear wheel radius = 0.146m

Inertia of Kart at crankshaft = 163.6kg * (0.146 m)^2 * (10teeth/82teeth) = 0.426 kg m^2

So the clutch is less than 1% of the system inertia. So if one clutch is 10% better than another, that would only be a 0.1% performance gain.

I ignored a few things, such as rotational inertia of wheel/axle brake assemblies, which would reduce the performance gain even more.

Please feel free to comment or correct me.

I ran kt100 for a few years with both clutches. Never noticed a difference on track. Only thing I ever experienced was that the L&T seemed to be more consistent and durable. Seemed like I was always tweaking on the horstman. Maybe just my experience with them though and not everyone else.

Agree with above calculations and seat-of-the-pants feel.

I’ve run Tomar, L&T, and Horstman, in single-disc, 2-disc, and 3-disc configurations and never saw any performance increase from one or the other based on weight.