Clutch

#21
I usually shoot for 6:1 ratio. Seems to give the best of both worlds.
One ratio fits all? No, too many variables. Power: A ratio that works well with a 7 HP engine may not work well with a 3 HP engine, for example. Tire OD: A ratio that works well with an 11" OD tire may not work well with a 15" OD tire, for example (search "effective gear ratio"). Rider weight: A ratio that works well for an 80 lb rider may not work well for a 230 lb rider, for example. I could list more variables but those examples are enough to make my point, plus the variables can be compounded: different HP engine plus different tire OD, etc. I'd say 6:1 would be a good starting point for a small-tire bike with decent power but it wouldn't be good for everything.
 
#22
If an 11T clutch is too hard to find, or overly expensive, you could go with the common 12T for a 6:1 ratio. I think that ratio would be too low when combined with your 15" OD tire but you can always change a jackshaft sprocket if need be. The less-common tooth count clutches tend to cost a lot more than the common ones, you may be able to buy a 12T clutch ($40 or less for a Max-Torque SS) and a jackshaft sprocket (probably $10-12) for less money than an 11T clutch. I prefer odd-number tooth count sprockets because they provide reduced chain and sprocket wear compared to even-number sprockets (was fairly common knowledge among motorcycle enthusiasts many years ago, requires a somewhat complicated explanation that I won't get into here) but you can't always get what you want, at least not at a reasonable price. I was looking for a 3/4", #35, 13T clutch a while back and saw some crazy prices before I found a Max-Torque SS for under $40 on eBay.
 

I74

Well-Known Member
#24
If an 11T clutch is too hard to find, or overly expensive, you could go with the common 12T for a 6:1 ratio. I think that ratio would be too low when combined with your 15" OD tire but you can always change a jackshaft sprocket if need be. The less-common tooth count clutches tend to cost a lot more than the common ones, you may be able to buy a 12T clutch ($40 or less for a Max-Torque SS) and a jackshaft sprocket (probably $10-12) for less money than an 11T clutch. I prefer odd-number tooth count sprockets because they provide reduced chain and sprocket wear compared to even-number sprockets (was fairly common knowledge among motorcycle enthusiasts many years ago, requires a somewhat complicated explanation that I won't get into here) but you can't always get what you want, at least not at a reasonable price. I was looking for a 3/4", #35, 13T clutch a while back and saw some crazy prices before I found a Max-Torque SS for under $40 on eBay.
Good info Charles, as always. ;)
 

toomanytoys

Well-Known Member
#26
One ratio fits all? No, too many variables. Power: A ratio that works well with a 7 HP engine may not work well with a 3 HP engine, for example. Tire OD: A ratio that works well with an 11" OD tire may not work well with a 15" OD tire, for example (search "effective gear ratio"). Rider weight: A ratio that works well for an 80 lb rider may not work well for a 230 lb rider, for example. I could list more variables but those examples are enough to make my point, plus the variables can be compounded: different HP engine plus different tire OD, etc. I'd say 6:1 would be a good starting point for a small-tire bike with decent power but it wouldn't be good for everything.
Can't argue with all that logic. Lol

6:1 is an easy starting point or close to. Adjust up or down as needed.

My rule of thumb is 5hp or under 6:1

6.5 I usually start at 5:1.
 
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I74

Well-Known Member
#27
Can't argue with all that logic. Lol

6:1 is an easy starting point or close to. Adjust up or down as needed.

My rule of thumb is 5hp or under 6:1

6.5 I usually start at 5:1.
Am 5 -1 on my slightly massaged GX-200, with a 14' tall rear tire & my 210+ lbs.,, & that sucker is quick !

I concur ''at least'' 6-1 is a good starting point ''also'',, on 4 - 5 hp engines.
 
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I74

Well-Known Member
#29
Am 5 -1 on my slightly massaged GX-200, with a 14' tall rear tire & my 210+ lbs.,, & that sucker is quick !

I concur ''at least'' 6-1 is a good starting point ''also'',, on 4 - 5 hp engines.
Added,,

Engines ''below'' 4hp, 7.5-1,, is a good starting point for those,, especially if someone over 180+lbs. is riding it.
 
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