work in progress

superhawk

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Sep 14, 2008
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Here's my project, I found the "Jeep" mountain bike, the back wheel came from a Honda moped.
The back wheel has a internal 12:1 reduction gearing with a disconnect lever and includes a drum brake.
The clutch housing is a Stanton unit machined with two sets of mounting holes for a Honda GX31 or a Chinese pocket bike motor, I also made the mounting system so I can fit other types of engines.The mounting system also allows me to shift to a different driven sprocket by sliding the motor mount sideways and up and down via the crescent shaped slot(spacer behind crescent slot makes up for the sideways movement)
Went for a test ride, but wasn't impressed with the power from the GX31, I haven't tried the 2cycle engine yet.
The drive chain is a #35, but chain noise is a problem as it's going at engine speed, I'll try a cogged belt drive as soon as I can find some pulleys and a belt. Maybe I get the belt and pulleys from a overhead cam engine core although I'm limited to 2:1 ratio.
The stock front derailler twist grip is changed to throttle twist grip by removing a internal flat spring.
I have to get a 1/2 by 1/8 chain to match front crank sprocket to the rear freewheel.
I'm keep on experimenting and see if I can get it to run quietly so I won't attract any unwanted heat.
 

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superhawk

New Member
Sep 14, 2008
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As luck would have it, I tried the Honda moped wheel in the swingarm and there was lots of room for the 2.50/17 tire.
The wheel mounts on 4 points and not thru the axle, so by using the stock swingarm rear mount on the moped wheel upper mount and welding "L" sheet metal brackets on the swingarm for the lower moped wheel mounts,I was able to maintain the same overall height. The moped wheel is about 5" shorter than the stock wheel.
The "L" brackets were the only welding done on the bike frame and the swingarm was not stretched, the rest of the motor mount was attached using the stock caliper brake studs and rear fender mounting points.
I just dug up a "Keystone" minibike gas tank which looks real cool on the frame. I will post pics later.
 

superhawk

New Member
Sep 14, 2008
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Update -decided to go for speed, for now, and mounted a 47cc pocket bike motor. I had to fabricate a new intake manifold since the motor is at a different angle and won't clear my motor mount.
While I was at it , I decided to make the intake flange fit several types of carburetors. The flange will mount the stock carb, a small diaphragm chainsaw carb, a Tilotson diaphragm type from a 100cc McColloch chainsaw and a Chinese Delorto copy.
The small brass nipple on the side of the flange is for the pulse line to operate the pump on the diaphragm carbs, I have yet to tap into the motor crankcase for the pulse line.
I started the motor up withe the stock carb and it was quite noisy even after repacking the little muffler on the end of the pipe with new fiberglass. I haven't gone for a ride with the 2 stroke yet. Those polished velocity stacks are just for show( had some spare time) they won't keep dirt out though.
I will update when I can.
 

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superhawk

New Member
Sep 14, 2008
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Did some work on the gas tank mount and tried some ideas. I had this Keystone minibike gas tank from way back, it's a little scratched up, but it's a good looking piece and I didn't want to spoil the outline of it by strapping it down.I made a frame for the tank which fallows the bottom shape of the tank and allows the tank to stand out.
I going to repaint the tank later and tidy things up.I also put a proper twist grip on it.
I have this Honda Passport (C70) front wheel and lo and behold it fits between the front forks with a shorter spacer and brake anchor, both of which I'll make tomorrow, but now the front end is lower than the rear.
It's beginning to be more motorcycle than bicycle now that it has D.O.T.tires and brakes.More later.
 

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superhawk

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Sep 14, 2008
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I decided to mount the exhaust lower, which requires re-welding and other mods. I tried a solid mount but after losing the header bolts and stripping out a hole during a ride, I went with a rubber grommet mount and safety wired exhaust bolts.
I also decided not to use the Honda Passport front wheel as then it would be more motorcycle the bicycle.
The muffler is now bigger internally , more holes(16) and a custom made aluminum shell filled with fiberglass.The cotter pin at the exhaust end is to keep from losing the end plug and the shell if the screws fall out of the end cap.
I changed the drive sprocket to one with 2 more teeth to change overall ratio from 22.5:1 to 20:1 for a higher top speed(27mph) and still be able to climb a modest hill.This was measured with a handle bar mounted cheap Ebay cycle meter which uses a spoke mounted magnet.
 

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superhawk

New Member
Sep 14, 2008
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Here's my next change. It's a 48.6cc pocket bike motor(44mm borex32 mm stroke) with a Chinese cloned ADA top end, piston and full circle crankshaft.They're very reasonably priced.
This cylinder has twin boost ports making it a 4 port motor with 14:1 compression.The mainstream pocket bikes are mostly "47"cc, but actually they are 40.2cc(40mm bore with 32 mm stroke).Should be a little more power.
 

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