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potbunny · May 21, 2012, 02:58 PM

Hi I like doing makeshift project so I decided to make a bike using a chainsaw motor. I need a little help though, I want to have some torque (I live in bloomington Indiana) to hit the hills but I also want speed to be able to ride on roads. I plan to mount the chainsaw on the rear rack of my 18 speed mountain bike. Now listen closely it gets complicated.
1. I will remove the pedal and weld new foot props.
2. I will instal a jackshaft with one large gear and a small gear behind that in place of the pedals (gears on right side).
3. I will wrap the chain from the chainsaw around the bigger gear.
4. I will wrap the chain to the original gear system around the small gear.
5. I now have a chainsaw bike with a transmission.

What I need to know:
1. what type of chainsaw to use (I want the bike to go up to 45-50 mph easily)
2. what size gears to use on the improvised drive shaft

I am not worried about the cc limitation on the chainsaw, just whatever will pull a 150 pound person without stalling or strain.

I will not buy a moped or motorcycle as I already have all the parts except for the chainsaw and gears.

Thanks very much!!

ma0641 · May 21, 2012, 03:08 PM

"40-50 MPH easily" and then stop with the bike brakes" Do you have a death wish? One little miscue and you are in trouble. Look at the history of Whizzer bikes to see how they worked.

potbunny · May 21, 2012, 04:51 PM

I have that worked out I bought a set of advanced handbrakes and I know to knly stop with the back one gradually.

ma0641 · May 21, 2012, 05:31 PM

If you Google. "Whizzer bikes" you will see another listing for a complete motor and parts for $179. Also on YouTube.

Fr_Chuck · May 21, 2012, 05:47 PM

I don't understand why you are not still using the back gears as they are, to allow you high and low gear ratio.

potbunny · May 21, 2012, 06:06 PM

I am but I thought I would need a gear ratio for the 2 gears I would have on the jackshaft in place of the pedals that the chainsaw chain and chain to the gears would be connected.

Fr_Chuck · May 21, 2012, 06:25 PM

I would go with the larger CC you can get, if you are getting too much, it can be handled by setting limits on the thottle, or handled though gear ratio

potbunny · May 22, 2012, 01:28 PM

I think I will get a 70cc or a 60 and use a 20:1 gear ratio. What do you guys think?

potbunny · May 23, 2012, 01:52 PM

For those of you who read my previous thread I had a change of plans. I will mount a pushmower engine to my bike. I am now indecisive on the gear ratio again. I am using a compound gear system on a mountain bike so I could use the bike gears as a transmission by using a jackshaft that leads a chain to the gears. I'm thinking maybe 3.5 horsepower an 150 ccs. Maybe more. I will put a carb with adjustable throttle in place of the non adjustable one. I want to go as fast as possible, so I need a good gear ratio. And should I mess with the governor? Or leave as is? Plus when starting I start in the first gear? I keep hearing it oppositely. I want to go REALLY fast. Should I use a bigger motor? It will be a race bike/moped Haha