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Old 08-18-2019, 09:30 PM
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itsid itsid is offline
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Originally Posted by zbillz View Post

Put a 15 tooth converter sprocket to get a little more mph and it looks like it lost some top speed...could only get around 22 mph at 3650rpm.
Almost looks like the belt on the driven side of the converter does not pull all the way in when the kart is at its top speed.

Any ideas on why this would happen?
SURE, craptacular gear ratio!

with a chain ratio of 3.67:1 you just do not have enough torque for the TC to shift all the way up,
essentially to 3.3:1

luckily, the 9.9:1 at take off keeps the belt from shredding,
but still the ratio is just insanely bad, even for a lightweight pack and small wheels.

what you want is to hit the calculated speed with the gear ratio you set.
and you haven't even with the 12T TC sprocket (assuming true 11") .. 28.6 would have been your goal, not 26'ish

Ideally you measure from the center of the axle down with your kid seated,
then multiply by two to get the effective wheel diameter
and use that for calculations

say 10.5" of effective wheel diameter bring the sped down to 27.3 mph
a straight 10" to exactly 26 mph

And that's why effective wheel diameter and some extra effort can be your friend.

I highly doubt the 10 horses btw...
since if it really had 10 horses
it'd also had the torque to reach top speed with your terrible ratio btw.
(as long as the kid's not growing that is)

So IMHO: back to the 12T and get a proper measurement..
maybe loose a tooth or two on the axle (which is a totally different thing than adding two teeth to the TC!!!)

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