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This design directly drives the rear gear cluster of multi-speed bikes. It bypasses the pedal crank altogether so is not to be incorporated on non-reliable bikes unless you modify it to drive a crank freewheel. The cost of parts is $53 (+shipping) w/o the $40 cost of the pull starter accessory (which is needed since you can't pedal drive the bike to start it). If I did this to my bike I would always carry a chain breaker and extra chain that I could connect between the pedal crank and rear gear cluster if the engine ever quit and I was far from home. Total cost is $93 + around $25 shipping + cost of making the jackshaft support. So maybe it isn't a great saving but it's good info that others with specialized modification projects may make use of.
Homemade jackshaft
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9 tooth sprocket with 3/16" keyway, 1/2" pitch x 1/8" width (standard BMX non-derailer chain width but will work on rear gear cluster) $14
http://www.sickbikeparts.com/catalo...ducts_id=31&osCsid=iarb58el5bs54ap8dg5okvj4v7
17 tooth sprocket 5/8" Bore, 3/16" keyway, for 415 chain $18
http://www.sickbikeparts.com/catalo...ucts_id=100&osCsid=iarb58el5bs54ap8dg5okvj4v7
Jackshaft Bearing 5/8" ID x 1 3/8" OD $2.49 (buy two)
http://www.mfgsupply.com/m/c/AZ8205.html
or http://www.sickbikeparts.com/catalo...ucts_id=128&osCsid=iarb58el5bs54ap8dg5okvj4v7
Jackshaft 5/8" OD x 4.5" long x 3/16" keyway. $4
http://www.mfgsupply.com/m/c/AZ8175-4.html
#415 half link $1.39
http://www.mfgsupply.com/m/c/11-415.html (or
http://www.partsstorellc.com/servlet/the-844/Half-Link-#42/Detail)
3/16" x 3/16" x 1-1/4" Key Stock $.32 (buy two)
http://ombwarehouse.com/3-16-x-3-16-x-1-14-Key-Stock.html
Lock collar 5/8" $1.25 (buy four)
http://ombwarehouse.com/5-8-jackshaft-collar.html
Bearing hanger, jackshaft weldment. 1-3/8" ID x 3" OD, 1/4" thick. $2.29 (buy two)
http://www.mfgsupply.com/m/c/AZ8128.html
Centrifugal Clutch and Pull Starter Kit $40
http://www.gasbike.net/bike-motor-engine-centrifugal-clutch.html
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Chain Breaker #35, 40, 41, 42, 43 or 50 $13
http://www.mfgsupply.com/m/c/32-1733.html
(or http://www.staton-inc.com/store/products/Chain_Breaker_35_410H_415H_41_40_and_50-402-35.html)
Homemade jackshaft
--------------------
9 tooth sprocket with 3/16" keyway, 1/2" pitch x 1/8" width (standard BMX non-derailer chain width but will work on rear gear cluster) $14
http://www.sickbikeparts.com/catalo...ducts_id=31&osCsid=iarb58el5bs54ap8dg5okvj4v7
17 tooth sprocket 5/8" Bore, 3/16" keyway, for 415 chain $18
http://www.sickbikeparts.com/catalo...ucts_id=100&osCsid=iarb58el5bs54ap8dg5okvj4v7
Jackshaft Bearing 5/8" ID x 1 3/8" OD $2.49 (buy two)
http://www.mfgsupply.com/m/c/AZ8205.html
or http://www.sickbikeparts.com/catalo...ucts_id=128&osCsid=iarb58el5bs54ap8dg5okvj4v7
Jackshaft 5/8" OD x 4.5" long x 3/16" keyway. $4
http://www.mfgsupply.com/m/c/AZ8175-4.html
#415 half link $1.39
http://www.mfgsupply.com/m/c/11-415.html (or
http://www.partsstorellc.com/servlet/the-844/Half-Link-#42/Detail)
3/16" x 3/16" x 1-1/4" Key Stock $.32 (buy two)
http://ombwarehouse.com/3-16-x-3-16-x-1-14-Key-Stock.html
Lock collar 5/8" $1.25 (buy four)
http://ombwarehouse.com/5-8-jackshaft-collar.html
Bearing hanger, jackshaft weldment. 1-3/8" ID x 3" OD, 1/4" thick. $2.29 (buy two)
http://www.mfgsupply.com/m/c/AZ8128.html
Centrifugal Clutch and Pull Starter Kit $40
http://www.gasbike.net/bike-motor-engine-centrifugal-clutch.html
---------------------------------
Chain Breaker #35, 40, 41, 42, 43 or 50 $13
http://www.mfgsupply.com/m/c/32-1733.html
(or http://www.staton-inc.com/store/products/Chain_Breaker_35_410H_415H_41_40_and_50-402-35.html)
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