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Old 12-12-2017, 01:07 PM
harold harold is offline
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Default Sprocket Help.

I have a 27 tooth drive sprocket with a 5 hp honda and 12in tire . How many teeth should I look for on a new clutch?
Thanks.
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Old 12-12-2017, 01:18 PM
mckutzy mckutzy is offline
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First what is the machine it is on?...
Is that OD of tire or rim size??? We need the actual OD for the proper ratio estimate.
If that rear sprocket isn't replaceable, then you will need a jackshaft...

As a start you want a 6:1 ratio... So a 12t clutch and a 72t rear(in #35 chain) #40/41 10t clutch/ 60t rear..... Ideally... But it's a good start..
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Old 12-12-2017, 01:25 PM
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Thanks,145/70-6 for the tire,so I guess a jackshaft it is. Any recommendations for tooth count for the sprockets?
H.
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Old 12-12-2017, 04:22 PM
mckutzy mckutzy is offline
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Still need the actual OD of the tire? ...
What is the machine?
What is the tooth pitch of that 27t sprocket?
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Old 12-12-2017, 04:35 PM
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Quote:
Originally Posted by harold View Post
I have a ... 12in tire . How many teeth should I look for on a new clutch?
Thanks.
Quote:
Originally Posted by harold View Post
Thanks,145/70-6 for the tire
145 is the width in mm. Tire is 145mm wide. or 5.71" wide.
Aspect Ratio is 70.
That means the distance from the outer edge of the rim to the outer edge of the tire is 70% of the tire width. 0.70*5.71"= 4"

Rim is 6"

So the tire should be 4" + 6"(Rim) + 4" = 14".

Show us some pictures.
How much does the kart weigh?
How much does the driver weigh?
What kind of rear sprocket? #420? #35"? # 40?

Something like 10T on Clutch to (22T - 24T) on JS, then 10T on JS to 27T on Rear.

Or 12T on Clutch to (33T - 35T) on JS, then 12T on JS to 27T Rear.

Or you could Replace the tiny rear sprocket. BEST OPTION

Or you could try a Torque converter with 7" pulley and 8T sprocket.
With 14" Tires, that would give you 40mph at 3600 RPM. That option costs around $100 and I'm not sure it will work. It should do ok I think, but high gear will be 3.8:1. It might be possible, I dunno. I bet it will be ok if the weight isn't too much and you don't have many hills.
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Old 12-12-2017, 06:32 PM
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Trust me, mathematically, they are 14". In reality, much closer to 13"...sooo, 13.5 at max for figuring ratios.
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Old 12-12-2017, 08:12 PM
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no matter what clutch.. you need a different rear sprocket!

(even a 2:1 wet clutch wouldn't do!)

'sid
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