need chain buying advice

brucemg51

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Jul 10, 2008
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I'm going to mount a 42cc chain saw engine over the rear wheel. I need to get the right chain to run from the sprocket on the engine to the sprocket on the wheel. How do I know which is the right chain to use? I've seen what they call BMX chain, for single speed bikes, and another kind for multi-speed bikes. Can I use bicycle chain or do I need heavier chain? How do I know if the chain will mesh with the teeth on the sprockets? Is there some sort of chain guide I can refer to?
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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What sprocket are you using on the rear wheeL You'll need a large one...50-80 teeth I'm guessing. The sprocket on the chainsaw won't work I don't think with bike chain or any other type of chain but the saw blade. You will likely need to replace the clutch with one more suitable.
 

brucemg51

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Jul 10, 2008
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What sprocket are you using on the rear wheeL You'll need a large one...50-80 teeth I'm guessing. The sprocket on the chainsaw won't work I don't think with bike chain or any other type of chain but the saw blade. You will likely need to replace the clutch with one more suitable.
One reason why I really like the idea of using the chain saw engine is that it has a centrifugal clutch. Is it not heavy duty enough to drive the bike and would burn up? I don't know what sprocket to use on the rear wheel, but yes, it would have to be a large one. The whole chain/sprocket thing is confusing to me. Wouldn't the number of teeth and diameter of the sprocket determine which chain would work best on it? Am I overthinking the whole thing? I have a tendency to do that, but that's the result of too many years of not thinking enough and having things blow up in my face.
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
235
63
up north now
Well for starters, the engine sprocket/clutch won't work with a roller chain because it's set up for a chainsaw blade, so you'll have to find another centrifugal clutch.

I would suggest a #41 chain and sprockets, or #35 because both are readily available and so are clutches and sprockets to go with them.

I'd start in the neighborhood of 8 or 12 to 1 reduction. You will have to consult more knowledgable persons on the final drive ration.
 

deacon

minor bike philosopher
Jan 15, 2008
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I am running a 33cc chainsaw as a friction drive. I thought about having a sprocket welded to the one that is already on the end of the clutch on my chainsaw but decided against it. I hate drive chains. but you might give that some thought if you have a problem finding what you need.

If you go with the number 41 chain you can buy a motor bike sprocket that goes onto the spokes of the rear wheel
 
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brucemg51

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Jul 10, 2008
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I am running a 33cc chainsaw as a friction drive. I thought about having a sprocket welded to the one that is already on the end of the clutch on my chainsaw but decided against it. I hate drive chains. but you might give that some thought if you have a problem finding what you need.

If you go with the number 41 chain you can buy a motor bike sprocket that goes onto the spokes of the rear wheel
I might try a friction drive, but wouldn't that require a vertical shaft drive engine, not the horizontal drive on the chain saw? Also, what about belt drive?
 

deacon

minor bike philosopher
Jan 15, 2008
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no it requires horizontal vertical shaft engines won't work.

If you really wanted to get cool, you could take the friction clutch bell off and have your friction drive welded to the gear on it, With a little luck the clutch will be strong enough to work,

Then you would have the best of everything. The recoil starter would be there. You could start it with the friction drive engaged since it would only move when you reved up the engine.

I took off my clutch so I don't remember how it attached. I expect you could work it out though.
 

brucemg51

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Jul 10, 2008
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If I'm visualizing this correctly, the drive shaft coming from the side of the engine is somehow going to be in direct contact with the rear wheel, either on the rim or the tire. Something would have to replace the chain saw sprocket that's on the shaft now. Is this correct? Are there any diagrams of this setup that I could see?
 

deacon

minor bike philosopher
Jan 15, 2008
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I don't have a diagram of mine but you have the idea. The engine hangs on the side of the bike. The drive shaft has a drive roller of some kind attached. It turns against the wheel which in turn makes the wheel turn. It is the most simple form of bike transport system.

I wish I could remember how the clutch bell was attached to the motor of my chainsaw engine. I am out of the shop for the night but tomorrow I will shoot a picture of my chainsaw engine set up. I don't think they get any more simple than my mount. If you can use your centrifugal clutch it will be even easier to mount.
 

brucemg51

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Jul 10, 2008
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Doesn't the engine hanging off one side of the bike cause the bke to be unbalanced? Also, I've noticed that since the tire is going to rotate in the opposite direction of the engine crank, I'll have to mount it backwards, which leaves the exhaust blowing up my butt.
 

deacon

minor bike philosopher
Jan 15, 2008
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One thing at a time.

Weed eaters generally run counter clockwise, my chain saw ran clockwise. Pull your starter and look. If it runs counter clockwise you have to mount it on the left side of the bike looking at it from the rear. If it runs clockwise you need to mount it on the right side. The Engine should spin in the reverse direction from the way you want the tire to turn. It's like a gear. You can also mount them in any position relative to the bike seat. If the exhaust is pointed at you just rotate the engine 180 degrees. You can even mount them upside down, I have done that now and then. Though it shouldn't be necessary for you. My chainsaw mounted on the right and everything was upright just fine. I'm gonna go down and make you some pictures now.

The hanging off is no big deal. I hang them off the front or the rear all the time. It won't cause you a problem. I have terrible balance issues with my body so if I can balance it anyone can.



If all else fails, the engine can run backwards anyway. use a pull rope and wrap it backwards., (Not recommended)
 
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brucemg51

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Jul 10, 2008
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Thanks for the info and pics. I think this just might work! I'm sure I'll have many more questions once I really get into this project.
 

Radmanfly

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Jul 28, 2008
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Oswego, NY
www.farleysradiator.com
I'm going to mount a 42cc chain saw engine over the rear wheel. I need to get the right chain to run from the sprocket on the engine to the sprocket on the wheel. How do I know which is the right chain to use? I've seen what they call BMX chain, for single speed bikes, and another kind for multi-speed bikes. Can I use bicycle chain or do I need heavier chain? How do I know if the chain will mesh with the teeth on the sprockets? Is there some sort of chain guide I can refer to?
This may come in handy:

Guide to Roller Chain

There were many different manufacturers of minibikes back in the 60's and 70's but most of them used one of three different size roller chain. You may see chain size referred by what pitch is has. The pitch is simply the distance from pin center to pin center. If you need new chain and your having difficulty determining the correct size that you need. Here's some information that may be helpful.

Number 35 Chain: Pitch = 3/8" | Roller diameter = 3/16" | Roller width = 3/16" | Pin diameter = 1/8" | Tensile = 2,100

Number 41 Chain: Pitch = 1/2" | Roller diameter = 5/16" | Roller width = 1/4" | Pin diameter = 1/8" | Tensile = 2,000

Number 40 Chain: Pitch = 1/2" | Roller diameter = 5/16" | Roller width = 5/16" | Pin diameter = 5/32" | Tensile = 3,700

Number 35 was uses on most all 4-5-6 inch wheel minibikes while 41 was used on larger minicycles such as Rupp Roadster II and Speedway. Number 41 chain will not run on a number 40 sprocket. Number 40 chain will run on a number 41 sprocket but it will be wider than needed. (like so many China bikes!)

SPACE CHAIN

Space chain is handy if you have sprockets that don't align properly. On space chain the outer links are just a bit wider so there is a small space between the inner and outer links. This space allows the chain to flex side to side much more than standard roller chain and will not run off the sprockets as easily. Although space chain is available in most sizes it is usually not a stock item and may be a special order.