Please critique my HF 79cc 7 speed idea...

M

macarollo

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I just sold my 196cc push trailer and now I am itching to build something new... Take a look at my picture and tell me what you think. I do not own this bike, but saw it at walmart today and thought it would be nice to have full suspension.

The idea would be to use a jackshaft and connect the chain to the bikes gears/derailer so it can shift as well. I would have to remove the chain going to the pedals since I cannot have two chains going at once.

I would turn/move the derailer forward (counterclockwise).

One concern I have is that not enough chain would be in contact with the bike gears because of how the engine drive chain is positioned. This might cause jumping of the gears.

It is not drawn exactly to scale and most likely the jackshaft and engine would be closer to the seat than pictured.

Any thoughts?
 

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There was a guy who built a side mounted honda GX50 next to his peddles on the Ecomodder website forum. He had to remove his peddles but he sure did haul *** while shifting gears. Let me see if i can find it. The problems i can think of are the peddle chain if you want to keep the peddles and the chain size might would be a little weak for the power of 2.5 motor. Won't know until you try though.
 
IMO, if you're going to lose the pedals, save both time and money and pickup a used Honda.
 
kerf is probably right on that one. But on the other hand, half the fun is in building something new that's all your own, right?

So....How about a very solidly mounted idler sprocket (or even pulley) that will give you more tooth coverage? It would have to be tough. But if you could manage that it would remove the only source of trouble that's obvious at a quick glance.
 
IMO, if you're going to lose the pedals, save both time and money and pickup a used Honda.

I assume you mean a used honda motorcycle or dirtbike. If that is the case I already have a motorcycle.

I think I build the entire thing for under $300, including the bicycle.
 
Don't mean to throw cold water on your plan, just an observation. In order to do this you'll need about 18 -20 / 1 reduction, so some serious jack shafting is in order. I have been thinking about a plan to jack shaft my Staton chain drive into a Sick Bike Parts chain ring freewheel that directs the engine power through the pedals. The freewheel allows you to use the engine or pedals independently of each other and have full shifting on the dérailleur.

This can be done but it ain't gonna be easy or cheap. Right now my Staton is setup with a two speed on the chain drive giving me 18/1 for cruising and 23/1 for hills. Don't know if I'll fool with it or not.
 
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after a little more thinking I came up with a new idea. I would buy a front freewheel so I could pedal and use the engine. I would use a chain running to a jackshaft then to the front freewheel sprocket.

Then I would have the standard chain running from a second freewheel sprocket to the rear derailer.
 

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Won't need 18 or 20 to 1 (that is the reduction for engines with a higher rpm range), but a nice 7 to 9 to 1 would be good. And you're right, the front freewheel will be a good idea.
 
if you use a 5:1 scooter tranny at the engine you will automatically have the drive on the right side of the bike.

from there you could go directly to the front freewheel. the bike gears would give you enough added reduction.

OR, you could put a jackshaft (like the second drawing) to keep the chain loops shorter, which is a good idea.

the fly in the ointment will be getting a spring loaded tensioner in the lower loop going to the freewheel, since the chain slack will alter each time the suspension moves.

steve
 
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