My first motorized bike build-four stroke honda

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cooperDG123

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This is my first bike build ever so cut me some slack. It's got a four stroke Honda 50cc 3 speed engine out of a crf50. It started as an old schwinn road bike. It has been cut stretched and reinforced heavily. The bottom two frame pieces have not been welded in yet. In the pic they are just pvc mockups. This bike will use a jack shaft system to combat the wide offset of the motor. The jack shaft will also have a large disc brake on it. Pedaling isn't that bad because I made some custom wide cranks to fit around the motor.

Let me know you guys think. Any ideas for improvements?
 

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MotorBicycleRacing

MotorBicycleRacing

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Jul 28, 2010
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cooperDG123 said:
This is my first bike build ever so cut me some slack. It's got a four stroke Honda 50cc 3 speed engine out of a crf50. It started as an old schwinn road bike. It has been cut stretched and reinforced heavily.

Let me know you guys think. Any ideas for improvements?
Click to expand...
Awesome custom build. I hope that you can bring it out to the Oct 17th
Socal Motor Bicycle Racing event in Apple Valley. :)

You will get to meet some of the leading bike builders from Socal and beyond.
 
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cooperDG123

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MotorBicycleRacing said:
Awesome custom build. I hope that you can bring it out to the Oct 17th
Socal Motor Bicycle Racing event in Apple Valley. :)

You will get to meet some of the leading bike builders from Socal and beyond.
Click to expand...
Thank you. Anywhere I can read more about the event? Do you have to be an adult to race? I'm 16.
 
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curtisfox

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Don't want to big a disk on the jack shaft ,as the gearing multiples the the stoping power and may be hard to control. Sure is a KOOL build ....................Curt
 
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cooperDG123

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msrfan said:
Great looking frame. Can you mount the engine lower to improve the CG? You'll appreciate it while cornering.
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I really wish I could, but mounting it lower would make pedals and a jack shaft almost impossible. I thinks when I'm done with this I'll start a new one but build it 100% from scratch, no bicycle frame.
 
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cooperDG123

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curtisfox said:
Don't want to big a disk on the jack shaft ,as the gearing multiples the the stoping power and may be hard to control. Sure is a KOOL build ....................Curt
Click to expand...
I'm not sure I have any other options I've got a sprocket on bothe sides of the wheel. Any one ever use the the sprocket as a brake rotor?
 
KCvale

KCvale

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Feb 28, 2010
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cooperDG123 said:
I'm not sure I have any other options I've got a sprocket on bothe sides of the wheel. Any one ever use the the sprocket as a brake rotor?
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You might be able to fashion a disc brake if it was mounted between the chain to and from path and used a sprocket big enough handle it.

Actually a couple of V-brake calipers might be easier.

Have you considered how you will shift the engines tranney?
It is pretty cumbersome to try to use a foot shifter from moving pedals.
 
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cooperDG123

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KCvale said:
You might be able to fashion a disc brake if it was mounted between the chain to and from path and used a sprocket big enough handle it.

Actually a couple of V-brake calipers might be easier.

Have you considered how you will shift the engines tranney?
It is pretty cumbersome to try to use a foot shifter from moving pedals.
Click to expand...
Not having been on any motorized bikes, I don't know if regular v brakes front and back will be sufficient. Does any one have an opinion on that? I'd love for it to be that simple, I already have a mount on the front forks.

Shifting is a tough on. Suicide shifters sure do look cool and would work for the application but I prefer to keep both hands on the bars whenever possible.
 
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KCvale

KCvale

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Feb 28, 2010
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cooperDG123 said:
Not having been on any motorized bikes, I don't know if regular v brakes front and back will be sufficient.
Does any one have an opinion on that?
I'd love for it to be that simple, I already have a mount on the front forks.

Shifting is a tough one.
Suicide shifters sure do look cool and would work for the application but I prefer to keep both hands on the bars whenever possible.
Click to expand...
What I meant was using a couple of V-brake calipers was to squeeze your sprocket, but V-brakes front and rear work for the most part well if you are not gong crazy speeds.

An electric solenoid attached to the shift lever out might work.
I gave that some thought for my MotoPed but just made a double side foot shift lever.



Cumbersome, but at least it's a down foot push to up and down shift.
 
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cooperDG123

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KCvale said:
What I meant was using a couple of V-brake calipers was to squeeze your sprocket, but V-brakes front and rear work for the most part well if you are not gong crazy speeds.

An electric solenoid attached to the shift lever out might work.
I gave that some thought for my MotoPed but just made a double side foot shift lever.



Cumbersome, but at least it's a down foot push to up and down shift.
Click to expand...
Aha I see what you meant. I actually have an oem honda heel toe shifter from a ct90 that should work well
 
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cooperDG123

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Apr 16, 2012
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I believe I have found a solution to my shifting problem, it's not ideal but I think it will work. The top lever will shift up and the lower lever will downshift. Shouldn't be to hard to rig up with just brake cable. Switching steen levers isn't as hard as I thought it would be. The only possible problem I see is not having enough travel or pulling power with the cables. Brakes will be on the throttle side, one lever will actuate Both front a back brakes.
 

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