After some advice

[Jmart432]

Hi guys im building a go kart and I already have a back axle and tyres off a quad bike. The sprocket on it is 50t and the back tyres and 19 inch. It seems that the smallest sprocket i could get for the clutch would be 10t and that seems that it would bw geared to high, especially since I live in a hilly area.
Would someone be able to tel me either what size wheels i would need on the back or what size back sprocket i would need to suit a hilly area with a solid back axle driven by a 6.5hp motor on a mix of road and gravel.
Thanks in advance guys!

 

[OzFab]

Ok first, the sprocket from a quad bike will most likely be a different pitch to that used on a go kart, probably in to 50's range so, you will need to change it anyway...

From the info you provided, you will need an axle sprocket somewhere in the 80's (tooth count) or somewhere in the 60's with a TC (torque converter) which can be found from around $100 & are highly suggested for off road & hilly terrain...

A TC gives you the best of both worlds as it starts out at a low ratio (around 2.5:1 IIRC) & works its way up to 0.9:1 at full speed...

Using the above figures as a guide, compounded with a 7:1 sprocket ratio, that will provide a 17:1 starting ratio & 6.3:1 at full speed...

 

[Jmart432]

Thanks for the reply. The rear sprocket and chain ive got is 420 pitch which i can find a clutch to match. As for the TC, would i be able to get away with 5:1 ratio on 18inch tyres with it? If not, ill probably keep the gearing and put smaller wheels on the back as they wont be hard to find and use a centrifugal clutch. With that 5:1 ratio and a clutch, what size tyres would you recommend?
Thanks for your help

 

[itsid]

7:1 is the highest ratio you'll get away with. (WITH a series30 TC that is)

if you insist on 5:1 gearing.. 14" is the largest rear wheel diameter that'd work well enough.
(again WITH a series 30 TC!!)

with just a clutch not exactly possible really... not reliable enough for clutches cheaper than a TC that is!

'sid

 

[landuse]

7:1 is the highest ratio you'll get away with. (WITH a series30 TC that is)

if you insist on 5:1 gearing.. 14" is the largest rear wheel diameter that'd work well enough.
(again WITH a series 30 TC!!)

with just a clutch not exactly possible really... not reliable enough for clutches cheaper than a TC that is!

'sid

This

Or you can just use a jackshaft to get lower gearing