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Old 05-16-2019, 03:22 PM
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KartFab KartFab is offline
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So when i first started messing with gear ratios on go karts i got a small axle sprocket and wanted to see how fast i could go.

What basically happens is if you gear with a small axle sprocket on a torque converter, the drive unit makes some really funny sounds and you slip your belt until all of a sudden it locks up fully when you start creeping forward. If the axle sprocket is too small, and the belt is fully engaged, it may even stall the engine or cause it to lug lug lug until you pick up a little more speed. Once you get going and actually hit the engines power band, its not so bad and the torque converter actually functions as it normally should.

That point between you being completely stopped up until the engine hits the power band on a normally geared go kart or mini bike is usually overcome with very little belt slippage.

Since you are running a little more hp, i think you will probably just spin the belt more and eventually get going rather than having the torque converter engage fully. IT will be a real jerky feeling when it does suddenly engage.

That is what happens at very low speeds. You might actually find it enjoyable to be going 40-60 mph in the powerband, but it will be a struggle for the belt and kart to reach that speed initially. It just wears the belt out and heats the drive unit up because of all the friction. Who knows, you might even see some belt smoke if you dont have enough teeth on the axle.

I havent done this with a 40 series, but the 30 series really did struggle to get going. Id assume you would have a similiar experience.

We often see people post about "why is my clutch burning up" and it is because someone swapped out the torque converter/jackshaft reduction for a centrifugal clutch.

We dont often see people post about "why is my torque converter burning up" because its actually kind of hard to ruin a torque converter when you gear with a smaller axle sprocket, it just mainly eats belts and you dont get those little butterflies in your stomach from acceleration. The end result is you just get poor jerky acceleration and your engine will lug down or smoke the belt because the kart cant accelerate like it is supposed to.

You can actually gear for a slightly higher top speed with a torque converter from the initial reduction, but it is not proportional to what you would think for a centrifugal clutch. All else the same, a 25 mph (centrifugal clutch) go kart can be geared for 35 mph with a torque converter, but not THREE TIMES FASTER. More like 40% faster, not 300%....

Again, nobody is stopping you from trying it out. Sometimes the best lessons are learned from doing and seeing what happens.
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