Author Topic: Motorized Bicycle  (Read 171 times)

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Offline JB Weld

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Motorized Bicycle
« on: December 29, 2020, 09:43:13 PM »
Starting a new project. Decided that a motorized bicycle would be a good idea. I told the father in law about my plans to use a chainsaw engine (gotta love strokers!) and he said he had some laying around. Got to his house one day to go deer hunting and he had a couple old McColluch Timber Bears sitting on his tailgate. After talking to him a bit about the missing parts we looked through his shed and found a couple more. I really thought the Timber Bears were the ticket as there were two, but shitty recoil and weak spark was uninspiring. So, decided to dump some premix into a newer, smaller, 38 cc machine and it fired right up!

Sold the other saws for almost nothing, and bought a carb kit for the little 38cc. Will post updates.

Offline sav0r

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Re: Motorized Bicycle
« Reply #1 on: December 31, 2020, 10:37:56 AM »
Make sure whatever bicycle frame you use has beefy rear dropouts. I live on a street with prominent bike lanes. I am about 2/3's of the way up the hill before getting to a large park that a lot of people like to bike to. Anyways, a guy absolutely ate shit right in front of my house on his motorized bicycle. The chain side dropout failed and supporting the rear wheel with one dropout didn't work out too well. The thing is, he was going like 30mph when it happened, and being on a bicycle instead of a motorcycle he only had a helmet on. The meat crayon was real.

It sounds like a fun project though!
www.chrislivengood.net - for my projects and musings.

Offline JB Weld

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Re: Motorized Bicycle
« Reply #2 on: January 03, 2021, 09:43:12 PM »
I'll keep that in mind. I have an old old Haro mountain bike that a neighbor left to the curb. It was either this or a freestyle 20" bike that was also left to the curb.

Had some time to work on the project today. Disassembled the mountain bike cranks. Then removed the tiny rear sprocket from the 20" bike and decided this will be the engine sprocket as it has 10 teeth.

The sprocket has a recess on the face that will be away from the clutch, so filled the recess with weld. I have to bore the center out to 14mm to accept the pilot bearing from the clutch. I tried to drill it out on my drill press and just created smoke. Must be hardened, so I'll take it to work and see if someone in the machine shop can give it some attention. I will remove the original chainsaw chain drive from the clutch and weld the 10 tooth to it.

Also started making a 48 tooth rear sprocket out of a table saw blade. I'll find a way to attach to the free wheel.

Offline m in sc

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Re: Motorized Bicycle
« Reply #3 on: January 04, 2021, 05:05:19 PM »
i love the idea of a motorized bike but id def take it too far and die.

I do have a really old 3hp allen bradley tractor, continental 'super 3' rope pull motor i want to stuff into a retro mini bike frame though. or make a battery charger out of. haven't decided yet.

def beef up the axle and dropouts & bearings.