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Discussion Starter · #1 ·
Hey guys..

Total newbie to the pocket bike/scooter world; don't know much about em yet, but reading and learning a bit more every day. Bought a 49cc engine off eBay to retrofit onto an old battery powered scooter. My goal right now on this first project is to get a complete usable unit before I start modding...stay tuned.


I'm a journeyman machinist by trade, now selling the cutting tools for a living. I have a vertical mill, crappy old lathe, horizontal band saw, chop saw, and a nice Miller stick welder to play with in my spare time. I enjoy boating in the summer (25' Robalo center console w/ twin 200hp outboards), snowmobiling in the winter (SkiDoo MachZ 1000), riding atv's (1989 Honda 250R), home improvements and other fun stuff.
 

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You need x amount of post before you can post in certain sections, and start threads in certain sections.

Welcome aboard! I've been here a few months, and there's a lot of short-time here today gone tomorrow, one questioners

But there's a group of gurus who have a mental encyclopedia and provide great, helpful and accurate advise and information.

I'm not huge on forums(with an exception of a couple others in the past) because they usually just have users who flame noobies and argue over whose is bigger but you won't find that here too much thankfully! Most of the active community here aren't kids and I think that's a contributing factor.

Again though, welcome!
 

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Discussion Starter · #7 ·
Cool; thanks guys, I figured as much as the post count. I know what you mean about guys flaming new people on forums, etc...I belong to a couple other forums for my truck, boat, sled, and four wheeler, and for the most part everyone is on there helping others.

My question is about a final drive ratio. I need to order a rear sprocket and machine some sort of a hub to have it fit what's on there now. The drive sprocket is a 6-tooth, #25 chain I think. The rear tire is marked 121/2x3.0. Where should I start as far as tooth count on the rear sprocket? I'm about 185lbs. Would rather have torque than speed for now; the engine is un-modded and will probably stay mild until I get everything working and proved out.

Thanks!
 

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Cool; thanks for your help. What is an optimal final drive ratio and is there a formula I can use to calculate it?

figuring out gear ratio is as easy as doing division.........7 into 74 is is 10.4:1...Race bikes are geared between 10-12:1 ratio..You want torque go 6/74.Youll have plenty of it...Go to the electric bike parts dealer and get a bigger rear sprocket that mounts into the freewheel hub....Theres Razor Electric and Honda Minimoto..
 

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Discussion Starter · #13 ·
Scratch that; the sprocket is threaded on and not pressed. Easy solution, I will just turn a new sprocket hub on the lathe. However; I had to flip the wheel around so the sprockets would be on the same side and the engine rotation would propel it forward instead of backward. I will have to mount the wheel in the lathe, turn the old threads off, and cut a left hand thread back on it- this way the engine will want to tighten the sprocket hub instead of loosen it.
 

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Discussion Starter · #15 ·
Looks like the 500w electric motor coming off of it (.67hp) was geared with an 11t sprocket, and 94t on the hub...an 8.5:1 ratio. I figure is little engine (even in mild tune) has to be 3x the power.

I ordered a 60 and 66t sprockets. With the 6t pinion, that should give me both a 10:1 and 11:1 ratio. At least a good starting point...I can definitely see ordering and tuning more in the near future!

Thanks
 
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