Final drive ratio question

Drivetrain upgrades, engine upgrades, or any other mods to gain speed or acceleration.

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BPT7594
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Final drive ratio question

Post by BPT7594 »

Hey,
As I am getting close to finish building my scooter's engine (75% done), the time has come for me to address the final drive issue :| .
In the past, when I modified my underbone's engine to get more out of it, the last thing I'd need to do is reduce the gear ratio by changing the front and back sprocket gears, since it would make the engine revs too high with the original gear ratio, at least that's what's traditional.
With scooter final drive I'm confused. I have 2 options, one is using the Kitaco gear which my friend tried without success (it howls too much on a stock 125cc), or use the Yuminashi gear (45/15) to lower my final drive ratio. Reggy himself recommends to try the stock 47/13 gears from the PCX 1st gen, which actually raise the gear ratio with the explanation that the esp gear ratio is too heavy.
Which option would be optimal here?. I weight 90kg, normally nothing more than 150kg is demanded from the scooter. I care about acceleration more than top speed to be honest. I am using the Torque Control Vario from Yuminashi with a shortened boss and at high speed the engine revs a lot lower than compared to my previous setup, so I take that reducing the gear ratio will result in an even more higher top speed?
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Oyabun
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Re: Final drive ratio question

Post by Oyabun »

I'll send over an excel sheet what I made to calculate final drive ratios. Will give you top speed and gear gear ratio changes for all possible combinations including the factory, Takegawa and Yuminashi and their combinations.
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Re: Final drive ratio question

Post by Dragon_uk »

Hi Oyabun.
Could you please pm me also this excel as I'm very interested in buying another pcx just to mod it heavily to make it a 250-300cc beater.
Thanks
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Rickjds
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Re: Final drive ratio question

Post by Rickjds »

Oyabun, please send me a copy too. Thanks!
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Mel46
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Re: Final drive ratio question

Post by Mel46 »

Dragon, you want to make a 250cc out of a PCX?? How in the world would you do that? I expect that you would have to swap out the engine, but won't that much power over torque the frame?
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Oyabun
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Re: Final drive ratio question

Post by Oyabun »

Holy thread resurrection.
Guys, send me your email addresses in PM and I'll shoot out the excel. It has some new options too - most of them are all factory combinations from pcx derivatives from other markets.
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Re: Final drive ratio question

Post by Dragon_uk »

Mel I'm thinking abour swapping it for 250-300cc but need to look closer into few engines to see how heavy the mods would need to be but would also like to take standard 125 and make 190cc out of it.
Frame will take it easily. Would only upgrade brakes for bigger disc at front and disc at back but would've got rid of abs.
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Re: Final drive ratio question

Post by Dragon_uk »

Oyabun could you please pm me as I can't seem to see your contact details in your profile
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Re: Final drive ratio question

Post by patmacessex »

Is this excel spreadsheet still available I bought the yuminashi 44 and 14 and at the moment I'm running the 44 with the stock 13 and 53 and I would like to know what the best set up would be I have the 51 counter gear as well...
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