What size jackshaft for comet 40?

[SharpTJ]

So I decided to replace my Manco 616's little Robin engine with a 13hp clone. I purchased a comet 40 and the engine, but never though about needing a different size jackshaft until I went to install the driven.

What size jackshaft do I need, 3/4"?
and I assume to sprockets/chain are #40?

And what sprocket would be optimal for a kart to have enough power to spin around and drift and still have a decent top end? I have 18" tires and currently 9/50 sprockets.

Sorry bout all the questions...learning as I go...

 

[Doc Sprocket]

If you have the CVT, just measure it for the jackshaft bore. There were a couple available sizes.

Chain pitch is whatever you select. #40 is most common. Gear deep with tires that large. 9 or 10T on the jackshaft, 60+ at the axle.

 

[SharpTJ]

If you have the CVT, just measure it for the jackshaft bore. There were a couple available sizes.

Chain pitch is whatever you select. #40 is most common. Gear deep with tires that large. 9 or 10T on the jackshaft, 60+ at the axle.

sorry,I meant to post this in the" engine and clutch" section. where can I purchase the jackshaft and what all is needed? From looking at some eBay does all the kits seem to include the shaft, bearings, couple sprockets, but no housing for it to sit in...

 

[KartFab]

toystory is spot on with his recommendation. You can get a bigger top speed without sacrificing low end torque though. (eg i have a manco 9t/54t and 22" tire set up with a 40 series, that is what came stock)

With your tires and 50t sprocket, a 9t will give you more torque than you need and a top speed of about 34 mph. A 10t sprocket would be PERFECT and give you a top speed of 38.5 mph.
(that is my opinion though so its up for debate, If i were to do this i would go with a 10t jackshaft sprocket.) if you are replacing chain/sprockets, make sure you get 420p chain to handle the extra torque. If you have a 41 sprocket/jackshaft sprocket you can use 420 chain on it.

A 5/8ths jackshaft would work too

 

[SharpTJ]

toystory is spot on with his recommendation. You can get a bigger top speed without sacrificing low end torque though. (eg i have a manco 9t/54t and 22" tire set up with a 40 series, that is what came stock)

With your tires and 50t sprocket, a 9t will give you more torque than you need and a top speed of about 34 mph. A 10t sprocket would be PERFECT and give you a top speed of 38.5 mph.
(that is my opinion though so its up for debate, If i were to do this i would go with a 10t jackshaft sprocket.) if you are replacing chain/sprockets, make sure you get 420p chain to handle the extra torque. If you have a 41 sprocket/jackshaft sprocket you can use 420 chain on it.

A 5/8ths jackshaft would work too

It currently as a 5/8" jackshaft but the driven seems to be 3/4"..my (wrong) assumption was that the new driven would be the same as the old one...thus I am now looking for a larger jackshaft I guess