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@danie avatar
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'57 VN2, '70 180 Rally, '80 P150X, '80 P200E, '05 GT200
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Location: George, South Africa
 
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@danie avatar
'57 VN2, '70 180 Rally, '80 P150X, '80 P200E, '05 GT200
Joined: UTC
Posts: 364
Location: George, South Africa
UTC quote
My VN2 Vespa has been upgraded to 150cc with 10" wheels. At present the 3-speed setup is as follows: 21t clutch gear with a 67t primary gear and the 1st gear has 56t. The original clutch gear had 22t, but then I had to rev the engine quite high to get going. With the 21t clutch gear, it feels better than before, but I am not sure if this is the best solution.

I now want to upgrade the gearbox to a 4-speed gearbox. The cush gear will have a 13-13-17-21 cluster and the loose gears will be 56, 42, 38 and 35. I can fit a clutch gear with either 21t or 22t, and I can change the primary gear between 67t or 68t.

I have put all these values into the Vespa Gearbox Ratios spreadsheet, but to be honest with you, I don't know how to interpret the results. Your help and recommendations would be appreciated.
⚠️ Last edited by danie on UTC; edited 1 time
@swiss1939 avatar
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P208, Stella VMC Stelvio 187, Stella 150, VNX1T, V9A1T, V9B1T, 02 Sportster XLH1208
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@swiss1939 avatar
P208, Stella VMC Stelvio 187, Stella 150, VNX1T, V9A1T, V9B1T, 02 Sportster XLH1208
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UTC quote
Post a screenshot of the results and I'm sure someone will be able to give advice.
@shipscat avatar
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Hooked
vespa 125 vnb1t
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Location: antibes , france
 
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@shipscat avatar
vespa 125 vnb1t
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Posts: 392
Location: antibes , france
UTC quote
have you tried this calculator
http://gearingcalc.free.fr/
it's in french but easy to understand[/quote]
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You're going to want to go to a 22/65 if going to something like a Pinasco or CC Corsa cylinder.

If using the old Indian Tuk Tuk cylinder, then maybe not. Can only imagine those things being a hair better then the old deflector setups. I don't mess around with them.
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@danie avatar
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Hooked
'57 VN2, '70 180 Rally, '80 P150X, '80 P200E, '05 GT200
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Posts: 364
Location: George, South Africa
 
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@danie avatar
'57 VN2, '70 180 Rally, '80 P150X, '80 P200E, '05 GT200
Joined: UTC
Posts: 364
Location: George, South Africa
UTC quote
To post a screenshot, is not going to be that easy. So I will summerise the results.

With a 21/67 I need 3365 revs to achieve 12mph and 6076 revs to achieve 56mph
With a 21/68 I need 3415 revs to achieve 12mph and 6166 revs to achieve 56mph
With a 22/67 I need 3212 revs to achieve 12mph and 5800 revs to achieve 56mph
With a 22/68 I need 3260 revs to achieve 12mph and 5886 revs to achieve 56mph
With a 22/65 I need 3116 revs to achieve 12mph and 5626 revs to achieve 56mph (Unfortunately I do not have a 65t primary gear)

So with the 22/67 combination I need the lowest revs, and with the 21/68 combination I need the highest revs.

Which is the best combination? Which combination will give me the most torque?

(Jonathan, I have fitted the SIP 151cc racing cylinder)
@gickspeed avatar
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danie wrote:
(Jonathan, I have fitted the SIP 151cc racing cylinder)
Unfortunately these are Indian made TUK TUK cylinders. i cannot offer advice since i don't fool around with these.

I run the Pinasco 160's with 22/65 setup, stock 3 speed gearbox. My long stroke Pinasco works a 23/64, original 3 speed setup. None of that helps you, but that gives you some idea of torque and power produced there.
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@danie avatar
UTC

Hooked
'57 VN2, '70 180 Rally, '80 P150X, '80 P200E, '05 GT200
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Posts: 364
Location: George, South Africa
 
Hooked
@danie avatar
'57 VN2, '70 180 Rally, '80 P150X, '80 P200E, '05 GT200
Joined: UTC
Posts: 364
Location: George, South Africa
UTC quote
I found a good gear ratio calculator on the SIP website, and I used the formulas to calculate the possibilities for my VN2M engine. I have added a summary of the various options available to me.

The original value for the 3-speed gearbox was quite low (12.18) compared to 14.47 for a P150. My mod (changing the 22 teeth clutch gear for a 21 teeth), made quite an improvement.

However, since I now am going for a 4-speed gearbox, things have changed again. I like the fourth option (green values), but what do you guys think?

Remember, I can only change between a 67t and 68t, and between 21t and 22t; the rest of the gears are fixed.
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