O&RBike

Having different mini bikes over the years we've fooled with lots of engines ..Clinton, Briggs, Tecumseh...but never one of these little O&R engines. Decided we better fire the motor and see what it was like. We made a temporary motor mount and clamped it to the old truck-hitch "dyno" lol we had made some years ago for testing small engines... Haha...looks lost sitting on the plate. Short fire up video: You may notice the recoil wanted to push the rope back out while running...the ratchet pawls were not retracting properly and needed a little adjusting/servicing (thanks Wallfish !)

We figured out early on working on the floor or bench wasn't going to cut it. We turned down a piece of black pipe and clamped it in the vise. Then we could drop the front fork neck over it and it conveniently allows us to swing the frame around from side to side. It would work better if we squared the bottom end to clamp it...instead we just cranked down on it hard enough to flatten the pipe lol... Here you see the new hub laced into the rear wheel and the 72T sprocket mounted...

Motivating this thing is going to take some serious leverage given the lack of HP and torque. We're shooting for a final drive ratio somewhere in the neighborhood of 20:1. There's a company called Stanton that makes all sorts of engine powered bike accessories including this rear hub with LH and RH threads on each end. One side gets a freewheel flange made to accept the (#35 chain) drive sprocket ...the other side gets a freewheel bike chain sprocket so you can stop peddling when the engine takes over.

Here's the bike blown apart... And back from the blaster's with some assorted parts we collected:

Next I sourced an engine from Joe Webber out of Missouri. I told him it was a father son project we were working on and he couldn't have been nicer or more accommodating. He gave us a great deal on the beautiful 1HP Compact III...looks like nos !

First order of business was to locate a suitable 2-wheeled candidate. A trip to the local Re-Cycle center turned up this forlorn looking mid-80's Huffy BMX in need of a good home. Hey at least it was made in the USA out of American steel and my SAE wrenches even fit it ! After some tense negotiating and arm wrestling it was acquired for the princely sum of $40 and tossed into the truck.

This started out as one of those ideas where my son and I just sat around wondering if it would work and sketching it out...the next thing I knew we were building it ! We've all seen the Tom Thumb and Micro Bikes...not very practical being 6 inches off the ground. Or the 26" cruiser bikes powered by the 50cc import engines...cool but it's been done a million times. We wanted to try something a little different. The aim was to build a lightweight, small frame bike to ride around the school campus. There are some pretty stringent rules as to what will qualify as a "motorized bike" vs a street legal machine that needs to be registered and tagged. Your not going to bolt a West Bend 580 into a Schwinn and go ripping down the bike lane and get away with it. Campus police are hip to people bending the rules. My son thought an old BMX bike might be an interesting platform...and the Ohlsson and Rice being a vintage "Made in the USA" engine was appealing to me. The biggest challenge will be wringing every bit of that 1 HP from what I see as an oversized model airplane engine. It may end up being an exercise in futility...but it will be an exercise in backyard mechanical engineering none the less and hopefully we'll both have some fun and learn stuff along the way.

I started this thread over on the Old Mini Bike forum where I am a member but I thought the folks over here might enjoy seeing it too. I have gotten a lot of help over here since joining and I surely appreciate it. Helping my son build a small (BMX) 20" bicycle that uses a 1HP O&R engine as a power assist. The idea will be to pedal it up to approx. 10 MPH and then let the motor propel the bike to (hopefully) 20 MPH if geared properly. Not sure if it work but it will be an interesting exercise for his mechanical engineering project. You may have to bear with me as I figure out how to cut and paste and upload images here....thanks !

'That would be most awesome if you are willing to part with it just name a price. I usually take forever to finish a project and it doesn't bother me to look for weeks or months for a part but this one is for my kid and you know how kids are he is all amped up to get it done so he can ride it around school. I'll take a look around first.

I am in Cranford...pretty much in the center of the state. How hard is it to find an original throttle...do they come up for sale on this forum or Ebay? Should I be searching under Ohlsson & Rice or Orline?

Curious what you guys are using for throttle cable setups on these. I'm trying to rig up a mini bike type twist throttle and looking for ideas. It doesn't seem possible that it will spring back to idle unless there is some kind of return spring in the handlebar throttle itself as the spring at the butterfly is so light. What does a stock throttle cable look like ? Thanks

One of the pawls was sticking...we removed them both, bent the springs up a little to add tension and put it back together with a few drops of oil on the pivot points.. Seems to work good now. Lot of end play in that half of the crank..!! Looks like .100 or more. If I'm guessing right the little brass eyelet in the center of the recoil cover acts as a thrust bearing to control this which is why you need to add a drop of oil every so often. What a strange little motor. We loosened up the cylinder and rotated the exhaust manifold where we needed it to be...seemed to go alright I don't think we damaged any of the gaskets. There was once or twice while we were running it over the course of the day where the motor appeared to "run away" ...that is the the throttle was in the idle position but the engine seemed to be accelerating. Maybe it was my imagination or I was breathing too much 2-stroke exhaust. :-/ Thanks for all the help so far...I'm sure I will need more. -G