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Old 10-15-2012, 12:33 AM
trackfodder trackfodder is offline
Motorized Bicycle Elite Member
Join Date: Sep 2008
Posts: 334
Default Poor folks have poor ways

Some time back I built a motorized bicycle with a 5-1/2 HP engine in it and used 2 jackshafts with one being a Sturmey-Archer 3-speed rear bicycle wheel transmission. It ran about 42mph at 3100 rpm on a governor (cruise control) full throttle in 3rd. I had a problem with the gas tank fuel gauge coming out so it got a chrome Hodaka tank, a carburator of a Lambretta scooter and a straight exhaust. Being somewhat high geared, it was terifyingly fast with no governor. Anyhow, I let it sit in the weather too much unused and the valves got sticky, and the control cables all siezed with rust. I am also building a Lotus 7 replica sports car from scratch and at the point of finishing the wiring. I am intimidated by the job and finding all sorts of other projects to keep from biting the bullet. refurbishing the motorbike is one of those. I had bought a 6-1/2 hp similiar motor from Harbor Freight Tool just because it was on sale for $89.99 from $149.99 so into the bike it went. The 2" pulley setscrew on the 5-1/2 was frozen so I found an adjustable pulley but it was slightly larger and when I tried it out found it to be very high geared, so decided to put an 18 tooth on in place of a 14 tooth one on one of the jackshafts. A problem arose. The jackshaft is a tube with 2 sprockets inserted in it with 2 ball bearings in each so it runs on a 5/8" fixed shaft welded to the seat downtube. The new sprocket has a large hole in it, slightly smaller than the hub of the smaller sprocket fitted into the tube. The problem was that to TIG weld the new sprocket the bearings had to be removed so they wouldn't cook. I needed a puller that would go into a 5/8" hole, expand behind one of the bearings, and allow me to tighten a nut and withdraw it into a tube. Such tools exist, but all the parts stores were closed and the set is pretty pricey. I went to Lowe's an bought a 3" X 5/8" bolt with some shank and a nut. I cut the head off and drilled a 9/32" hole 2" deep and reduced the diameter of the shank except for about 3/16" at the end so it would fit between the bearings to expand. Then I slotted it in quarters and ground flats on the threaded end. I cut off some metal tube big enough to fit outside the bearing and drilled a 5/8" hole in a bit of 1/8" steel. I inserted the tool in between the bearings and drove a tapered punch into the hole. With the sprocket in the vice, I placed the tube and drilled plate over the sprocket and tightened the nut while holding the bolt with a wrench on the flats. I was rewarded with a grudging grunt and another etc. and here came the bearing!!! I machined the teeth off the 14 tooth sprocket down to the diameter of the hole in the 18 tooth one and put a taper in the 18 so my friend with the Tig can fill it from one side. I don't know what to do with all that extra power, but at least it won't sound like a "Poppin' Johnny" going down the street. (single cylinder John Deere tractor for all you young city kids) I replaced the Schwinn spring fork with rigid so it doesn't feel like a bunch of rubber bands to steer.
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