Use current bicycle gears??

GoldenMotor.com

cschade

Member
Aug 8, 2014
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Hello, I'm thinking about building a motorized bike using a Harbor Freight 3hp engine. Two questions -- first, on the Harbor Freight website it says the shaft rotates counter clockwise. Is this counter clockwise as viewed from the visible end of the shaft? Also, I'm thinking about using the pedals of the bike as a jackshaft. For instance, mount the engine so the engine shaft is sticking out the left side of the bike as viewed from the seat. Then, run a chain from the clutch to a sprocket mounted on the left side of the pedal crankshaft, opposite of where the sprocket is normally mounted. Then, let the engine turn the bikes gears. I've attached a sketch. Can this be done. I'd have to cut off the pedals and mount foot pegs somewhere else. Thoughts?

.scratg.
 

crassius

Well-Known Member
Sep 30, 2012
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knew a guy just turned his pedal crank around to sit on left & reversed rear wheel and freewheel action
 

2door

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Staff member
Sep 15, 2008
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Check your local laws before removing the pedals. Some jurisdictions require them or they will call your bike a motorcycle and will require motorcycle registration, insurance, etc.

Do some reading here on the Harbor Freight engine conversions. Use the search feature or check the DIY section for non-kit engine installations. I feel you have a lot to learn before attempting this installation. Good luck.

Tom
 

cschade

Member
Aug 8, 2014
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Check your local laws before removing the pedals. Some jurisdictions require them or they will call your bike a motorcycle and will require motorcycle registration, insurance, etc.

Do some reading here on the Harbor Freight engine conversions. Use the search feature or check the DIY section for non-kit engine installations. I feel you have a lot to learn before attempting this installation. Good luck.

Tom
Thank you, and you are right -- I have a lot to learn! The only motorized bike I've built before was friction drive, so I'm not used to chains and sprockets :).bf.
 

cschade

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Aug 8, 2014
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Another question -- how many teeth should the sprocket be (with the chain running from the engine to the jackshaft). There are some pretty big hills around where I live, but I'm only 130 lbs. 30 tooth, 40 tooth, 60 tooth?
 

crassius

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Sep 30, 2012
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not sure if he turned the pawls around on it or it came that way, but I seem to recall it was threaded backwards too

this was maybe a year & 1/2 ago

you should try googling

he had a progressive drive on a 4-stroke that was a lot easier if it came out on the right side
 

BarelyAWake

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Jul 21, 2009
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I'm not recommending these outlets, dunno beans about 'em other'n they had the handy info to link - as always, shop around ;)

Flip-flop Hubs

Flip-flop, or double-sided hubs are threaded on both sides. Usually one side has a track-type threading, (with lockring) and the opposite side is threaded for a single-speed standard freewheel.

The usual way to use a flip-flop hub is to have a fixed gear on one side, and a single-speed freewheel on the opposite side. The freewheel sprocket would normally be larger than the fixed sprocket, providing a lower gear.



Cyclists would use the fixed-gear side for most pavement riding, and save the freewheel for off-road use, or for getting home when they tired. Having the freewheel larger than the fixed sprocket gives cyclists a lower gear when they are using the freewheel. This makes it easier to climb. Since riders can coast when they are using the freewheel, the lower gear is no disadvantage on the descents.

Single-speed freewheels are commonly used on BMX bicycles, most shops that deal in BMX parts will stock them. The common size used for BMX is 16 tooth, but 17, 18, 20 and 22 tooth freewheels are available.

Note, there are two types of hubs called "flip-flop":

Fixed/free, this is the type we speak of above, with a "track" side and a freewheel side.

BMX type...BMX flip-flop hubs have two different freewheel threads, a standard one on one side, and a special smaller-diameter freewheel thread on the other, designed to work with special small freewheels (14, 15 teeth.) These are now quite rare, but if one is calling around looking for "flip-flop" hubs, make sure to get the right kind.

http://www.bikesdirect.com/products/flipflop.html
& if you'd like a reversed freewheel w/that;

http://www.treefortbikes.com/product/333222380078/945/ACS-SouthPaw-Freewheel-1-and-8.html
 

cschade

Member
Aug 8, 2014
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0
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United States
Thank you for your help, everybody. I've been doing a lot of reading up on the subject, as someone suggested. Another question I have is: how would I go about mounting the larger sprocket on the cranks? And, what size sprocket would you recommend? I'm leaning toward a 50 tooth with a 12 tooth on the clutch, because I have a lot of hills where I live. What are your thoughts?