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Old 02-14-2020, 04:24 PM
courior courior is offline
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Default Axle Size?! for a big motor!

Hi all... My dream of having a shifter kart is a little closer.... My friend has just given me a 470cc Supermoto engine with around 45-50bhp. Im gonna of course go with a live axle setup, and although i understand the concepts of how to make a go kart, the experience is not yet under my belt.. So was wondering what size axle i should go with for this setup. I can reduce the torque with the sprockets, and it the motor has a 5 speed box. Ive seen 25mm solid axles which look pretty beefy, then from 30-50mm they are hollow. All ideas are much appreciated!

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Old 02-14-2020, 06:49 PM
mckutzy mckutzy is offline
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Off hand, get 1" to start... but mostly depends on what the hub size for the rims of the tires you are using is...

What is a "supermotor engine"???
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Old 02-14-2020, 09:27 PM
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we've had that exact discussion just a week ago..
and I stand by what I said: more diameter == more better!

and hollow isn't at all important, the diameter counts most

you wouldn't build a kart frame from massive half inch rods, would you?
you pick 1" thinwall tubing instead.. more beefy, less heavy...

while the single cylinders have some good torque..
I wouldn't try to reduce that... in fact you'll still need to up that a bit
because of the heavier weight you'll be going to move around

'sid
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Old 02-17-2020, 01:43 AM
courior courior is offline
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Thanks for the reply's lads.. yeah its what i thought, bigger is better. but i thought solid would handle torque better, the frame is thin wall box section yes, but it doesn't need to put up with twisting forces, more bending.. but then big v8 trucks have hollow drive shafts so there is that.

The "supermoto" engine is a Husaberg FC470e motor, 470cc, 45-50bhp depending on carb/tuning and a crap load of torque (1 cylinder). Supermoto is a style of motorcycle. The motor weighs in at about 25-30kg wet (im not a big guy but i can throw it around the shop quite easy with not much effort) so i dont think its THAT much more than the usual 140cc pitbike motors.. The motor is vertical tho so has a smaller footprint than the pitbike motor. For the hub i was thinking to get the rear wheel from a supermoto, remove all the spokes and rim, and then im left with the hub, which carries the sprocket and brake disc, then weld or keyway this to the shaft. The wheels are the unknown, i was gonna get the shaft first and then go with whatever wheels fit. I think normal go kart wheels will be fine, but i plan on perhaps road racing this thing if it comes out well so would like a little more ground clearance than normal as the roads here are not that perfect haha.
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Old 02-17-2020, 09:25 AM
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you misunderstood..

the engine weight is not what I meant.. I meant the kart is heavier than the bike was.

and the torque of the engine might be quite dramatic on the bike,
but it might not be as impressive on the heavier kart.

that's why I said you should -at first- not tamper with the gear ratio at all
since it has showed that most of the time the compensation you get
from swapping the large bike rear wheel against the small kart rear wheel
while sticking with the original sprocket ratio is just about perfect most of the times.

'sid
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