Changing crankset to 3-piece

Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
3,664
5
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Duvall, WA PNW
www.sickbikeparts.com
I photo-documented the steps of changing over to a 3 piece crank for general usage or for the shifter kit.

First is a picture of wrenched maniac aka lurch or "The Crank".

Then a pic of the dead carcass of a one-piece, or a piece de Ashtabula. Removed from a 1980's Columbia Bike. Note that it is, well, one piece - one forged piece.

Followed by the cleaning up of the bottom bracket to allow the cups to fit. Mostly raised metal, weld seam, paint and crud. Used a moto tool sanding drum. There is no way the cup could be pounded in without the clean-up, but be careful, it still needs to be a press fit. I smacked it with by dead blow hammer, a block of 2-ba-4 and hammer, and a ball peen with a brass drift.

The purchased assembly for under $20.
 

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Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
3,664
5
38
Duvall, WA PNW
www.sickbikeparts.com
Lemme know if you want details....not feeling particularly verbose right now! :crash::p
It's pretty straight forward, and the kit didn't come with any instructions. The conversion kit is boxed to be sold to the bike mech/shop.
 

pi-rat

New Member
Aug 7, 2008
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cant you make this into a shifter kit by putting a #420 chain sproket on the left side so it will spin te gears on the right? if it works ive got a 21 speed motorbike !!!! i think that i might have to cut off the pedals for it to work though and put a case over it so i dont cut off my leg on the chain and sproket.
 

Nitrohorse

New Member
Aug 1, 2008
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Pablo,
I'm real new to this motorizing a bike thing, so if I ask a dumb question, please excuse me. I was looking at some bikes at Walmart and Target. There's a crusier that I'd love to buy, but it has the one piece crank and I need the three piece due to my selection of a 4 cycle engine and the larger crank clearance it requires.
How do I know what kit I need to order so that I can use the crank arms that were supplied with the engine?
Thank you in advance,
Larry
 

SalisCruiser

New Member
Sep 28, 2008
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cant you make this into a shifter kit by putting a #420 chain sproket on the left side so it will spin te gears on the right? if it works ive got a 21 speed motorbike !!!! i think that i might have to cut off the pedals for it to work though and put a case over it so i dont cut off my leg on the chain and sproket.
would this really work?
 
May 10, 2008
83
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0
Nappanee, IN
cant you make this into a shifter kit by putting a #420 chain sproket on the left side so it will spin te gears on the right? if it works ive got a 21 speed motorbike !!!! i think that i might have to cut off the pedals for it to work though and put a case over it so i dont cut off my leg on the chain and sproket.
yep, jack sahft shifter setup with out the jackshaft.

you'll need to asses the power and torque of your engine to calculate the primary reduction needed form the engine output to your lefthand crank sprocket. it also depends on what speeds you want to achieve.

don't forget some sates require the pedals, be sure to check your local laws.

steve