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25cc engine bike drive gear

Old 06-15-05, 06:44 AM
  #1  
infinityeye
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25cc engine bike drive gear

Hi,

I am crazy


I want to put a 25cc engine on a rear rack. attach it to a 53t road ring that is bolted to the wheel on a bike. I have rebuilt this little engine and got it idling again. I have all the stuff worked out except the "front" sproket. Does anyone know where I can get a sproket or sproket/centri clutch that will attach to this motor? It has a bell centri clutch on it now that ends in a square taper for a worm drive (weed wacker). I am thinking I need to remove this clutch and hopefully find a bolt on clutch/sproket to get the drive line in place.
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Old 06-15-05, 07:42 AM
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I was going to build something like that but then I found these:
https://www.rabbittool.com/frames/frelcwhl.html
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Old 06-15-05, 08:07 AM
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Can I ask, what's the point of a bike that is self powered? Is the world becoming so lazy we can't even pedal bikes anymore?
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Old 06-15-05, 08:23 AM
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Isn't that the same thing as a moped?
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Old 06-15-05, 08:49 AM
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Try some whizzer places. They usually run belt drives to a sheave on the rear rim.

https://woodstockwhizzer.com/whizzer_Pictures.htm
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Old 06-15-05, 10:05 AM
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Originally Posted by Tweek
Can I ask, what's the point of a bike that is self powered? Is the world becoming so lazy we can't even pedal bikes anymore?

I have 10 other bikes and ride all the time. It's more of just liking to build something out of nothing. Your comment is rubbish anyway becasue there is a lot of sweet people who in fact are too lazy to pedal. I mean maybe you live where it is flat or something. Don't hate people just because they are not ultra cool like you.
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Old 06-15-05, 10:10 AM
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A motorized bicycle is like putting pedals on a car....whats the point. A bicycle is meant to be ridden under human power.
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Old 06-15-05, 10:14 AM
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Originally Posted by infinityeye
Don't hate people just because they are not ultra cool like you.
Why thank you, I knew I was cool, but not ultra cool.


Originally Posted by amahana1
A motorized bicycle is like putting pedals on a car....whats the point. A bicycle is meant to be ridden under human power.
Thanks for backing me up buddy.

Last edited by Tweek; 06-15-05 at 10:19 AM.
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Old 06-15-05, 10:30 AM
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The point is the building and then riding and smiling. If you don't see the point, just go back to your hole troll
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Old 06-15-05, 10:45 AM
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Originally Posted by infinityeye
The point is the building and then riding and smiling. If you don't see the point, just go back to your hole troll
Buy yourself a motorcycle, then you can be riding and smiling, and picking up chicks at the same time.
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Old 06-15-05, 02:06 PM
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I understand what you mean. I thought about doing it last summer, but built a tandem instead! I love the whole idea of just building things. Hope it all goes well for you, post some pics if you ever get it done.
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Old 06-15-05, 04:13 PM
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Originally Posted by infinityeye
The point is the building and then riding and smiling. If you don't see the point, just go back to your hole troll
This is the b-i-c-y-c-l-e mechanics forum. Little to do with engines.
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Old 06-15-05, 04:45 PM
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Well, well. This thread certainly brought the self-righteous snobs out from under their rocks. It's a sad commentary when all you've got to hang your self-esteem on is that maybe you pedal more than somebody else does.

Infinityeye, you go, boy -- build it; you don't have to prove your credentials to these naysayers. There are a hundred reasons why someone would build a motorized bike; some of them, like the joy of creating something have already been mentioned. I've been thinking about it myself. I've got half a dozen bikes and ride every day. My wife used to -- she's had some health problems and can't hang for very long anymore though; around the block is about it. I want to build one for her so we can go riding together again. If that makes either her or me a lesser cyclist in somebody's eyes, well -- I'll just have to hang my head and live with the shame.

Also, Oldroads.com has a discussion area for motorized bicycles where you might get more helpful comments. Good luck with your project.

https://oldroads.com/d_cst_def.asp?rec_count=1
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Old 06-15-05, 08:43 PM
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I think you will need a 3 or 4 tooth cog at the front end to match the engine speed to the wheel speed.
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Old 06-15-05, 08:46 PM
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Yeah InfinityEye, what mswantak said! Nourish that creative streak and go for it, don't even bother responding to the negativists. Where would we be without creative, inventive bicycle mechanics (ever hear of the Wright Bros?).
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Old 06-15-05, 09:00 PM
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I think there are some engines & systems available that use a direct drive to the bike tire. I know Fox model airplane engines made one years ago but I haven't seen one in a long time. But I think there are a couple of motors available from Europe that use direct drive to the tire that I saw a few months ago when there was a similar thread. Might try a Google search.
If you want one go for it. Who cares is it's not "PC" to some people.
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Old 06-16-05, 09:32 AM
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Originally Posted by mtbikerinpa
I was going to build something like that but then I found these:
https://www.rabbittool.com/frames/frelcwhl.html
Wow, that's the first hub motor system I've seen that's not butt-ugly! Thanks for the link!
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Old 06-16-05, 11:24 AM
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Originally Posted by AndrewP
I think you will need a 3 or 4 tooth cog at the front end to match the engine speed to the wheel speed.
That was going to be my input too. There's not much torque in a 25cc motor either. I think a 3/4 in the front and a standard 11-34T cassette, should get you going and keep you going quite fast.
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Old 06-16-05, 12:37 PM
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Don't complain when people gripe over you making a motorbike. This is bicycle forums and we like people power; deal with it or go elsewhere.
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Old 06-16-05, 12:50 PM
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Originally Posted by Enthalpic
Don't complain when people gripe over you making a motorbike. This is bicycle forums and we like people power; deal with it or go elsewhere.

Why exactly should I have to "deal with it?" You are a chump, chump
Go spew your emasculation frustration on someone else!

I thought this site was for real bike mechanics not chain store jerks with manicures. My bad.
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Old 06-16-05, 01:32 PM
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I agree as well. There's just something about a lot of mechanically-inclined people that makes them want to put stuff together to see if they can make it work.
For the last couple of months, I've been working on my home-built recumbent. A crazy mixture of three different bicycles and an old Nordic-Trak rowing machine...Ugly but functional.

People have been sticking motors in bicycles for a long time. My local Schwinn dealer has a GT cruiser-bike on the showroom floor with a cute little 50cc 2-stroker in the frame.

The guy has a stable of regular bikes; so as he notes, he's not out to offend people-power sensibilities with his project.
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Old 06-16-05, 02:58 PM
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Not saying don't do it; just saying this is not the place for it.
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Old 06-16-05, 05:27 PM
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Hmmm ... was it a "bicycle"? Is it still going to have pedals? ..two wheels? A chain? Sprockets (cogs & chainwheels)?
If so, it sounds like a "bicycle"! Why don't you post your question in a "bicycle forum"?
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Old 06-16-05, 05:48 PM
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Originally Posted by mtbikerinpa
I was going to build something like that but then I found these:
https://www.rabbittool.com/frames/frelcwhl.html
Leave it to the A&P to find the cool stuff! That's a very clean setup. Much cleaner than any I've ever seen in the past.

To the original poster, I'm still trying to envision how you'll mount a 53T chainring directly to the hub but I suppose it could be done. I'd be a little leary about the amount of torque the motor might generate. Also, are you going to try and retain the capability to pedal the bike or will this be pure motorised power?

The thing is, there have been plenty of motor-assisted bicycle kits already. Most of them drive the rear wheel through rollers though.

Now what I think would really be cool is to somehow make the world's first hybrid-electric motor-bicycle by combining that system that mtbikerinpa posted about and coupling your gas motor to an alternator (actually you'd want it to be a direct-current generator) to have it feed to the electric bus of the MEWS. It'd be nice to be able to split the flow to also recharge the battery at the same time. In this way, you'd have a bicycle that could be human powered, gas powered and battery powered at the same time. How's that for an engineering challenge?

Check out this webpage to see what some others have done and for further ideas.
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Old 06-16-05, 08:20 PM
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The cool thing with the rabbittool hub motor setup that I liked was that it is an efficent generator too when you are not using it. Pull back on the throttle and the generator can turn into a dynamic brake(tandem guys can appreciate that one). So it is a single gear rear with a freewheel(looking like a singlespeed) but you then have a cruise control. Would I use it for putzin around town, probly not. Thats for the play bikes. Training rides would still count, heck I could turn it to generate and make a bunch of resistance if I so chose.
For getting to work on time, it would be great. 20mile commute at 35mph sweat free.

On another note, a lot of municipa and state laws restrict motor-bike configurations. No chains or belts or it becomes a motorcycle. Hub motors are the only non-restricted way other than the roller on the tire(ala wizzer).
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