Building A Practical And Safe Motorbike Pt.1

Local time
6:43 AM
Sep 8, 2008
Bartlesville Ok
The basic design was familiar in the World War 2 years hauling defense workers to their jobs on very little gasoline, which was rationed. All sorts of small engines were used, but mostly washing machine and lawnmower motors. The basic Bartlesville bike was a rectangular frame usually of 1” angle iron that served as foot rest and mounting for brake and clutch peddles and in the middle a mounting plate for the engine. This was welded to the area formerly occupied by the peddle shaft housing and the center of the front portion welded to the front down tube. The frame was reinforced by a pair of handlebars cut and welded to the front corners of the rectangular frame and to the front down tube from the steering head which was re-curved to follow the wheel curve. . This makes a very strong structure, and serves as crash bars. The jackshaft housing was usually welded to the seat post and used 5/8” I.D. generator bearings. Many improvements were developed along the way and those are what I want to detail here. In the beginning, before Whizzer motorbikes, the rear drive pulley on the wheel consisted of a plywood pulley that was attached to the engine shaft and a vee groove cut into the edge with whatever we could come up with, like sharpened screwdrivers or if we were lucky, a genuine wood lathe tool. This was a tedious and very dangerous job at best and we just squinted and ducked, as we didn’t know what safety shields were. The insides were removed to leave about 3” of rim and the thing was attached to the spokes with lots of washers and screws. The metal Whizzer pulley sieve was the best thing to happen to the art. Some bikes used no clutch at all, and the rest took a cue from reel-type lawnmowers and used an idler pulley against the outside of the bottom run of belt from the engine to the jackshaft. The motor pulley usually was about 2” and the jackshaft pulley it drove was about 6”. The final drive was something like 2-1/2” driving whatever the Whizzer pulley was. The actual ratio was usually jiggled around until the thing pulled itself with reasonable authority and satisfactory speed. Our dynamometer was SHAWNEE HILL If you couldn't’t pull it, you didn’t have squat and everyone would laugh at you. When it came time for THE TEST, some folks would secretly drop moth balls in the gas tank to raise the BTU of the fuel for a few minutes to put out more power. The down side was it always grew crystals in the carburetor and choked it off, so a quick trip home was in order to rinse it out. I built my first motorbike in the 7th grade with a 5/8 hp. Briggs & Stratton WM out of a Maytag washer. It had a suction carburetor and a little square tank that mounted on the footrest frame. I could ride the 10 blocks to school and back all week on one tank of gas. I had no clutch and to stop, I put my shoe soles against the front tire behind the fork, since I had no front fender. If I stopped, I simply legged it along about 3 feet and the beast was running again. The throttle was a choke cable with a knob on it. It started a love affair that has lasted 57 years so far and I am just now finishing up number (approx.)14 The art was to build the best thing you could with what you could barter for, buy, or whatever. You also tried to dream up something that no one else had done. That made you noteworthy. My contribution to the art was to wrap the peddle chain around the coaster brake and pull it back with a screen door spring fastened to the seat clamp bolt at the top of the seat tube. This was a improvement over welding a lever to the sprocket and a clevis rod fastened to it. It was much easier to remove the rear wheel to fix the many flats. My 12th one was built on a Schwinn 20” frame with a 1-1/2hp Briggs& Stratton model N, which was the WMB with a gravity carburetor and an oil pump rather than a splasher on the rod. I couldn’t get ready to pay $45 for a Whizzer replica sheave, so I elected to use a chain drive final. I machined an aluminum hub which I sawed in half and bolted together on the brake housing inside the spokes. From this, 3 spacers extend through the spokes and a pedal sprocket is bolted to the alloy hub. Enough of the sprocket middle is removed so that the brake lever has room to mount. A brake sprocket on its hub is mounted on the jackshaft. The clutch is the usual idler pulley on an arm powered by a spring horse spring. It has a large washer welded to the top of it so that it can be held down to rope-start the engine and also has a motorcycle clutch lever on the handlebar. .Number 13 is an old Rollfast frame with a Schwinn spring fork. It had a 2 hp Lawson for a time but has been replaced with a 3hp Clinton from a 1968 Yazoo high-wheel lawnmower. It is also driven by a bicycle chain. I mounted a rubber tired wheel from a clothes dryer tub support on the crankshaft and it drives a bicycle generator so that I have lights whenever the motor is running. As on a bicycle wheel, the generator may be retracted for daytime running. The fuel tanks (2) are made from 4” dia. Exhaust tubing and the ends of 16 ga. Sheet were bulged by applying 6000 psi. on a rubber stopper while supporting the stack of ends on a large diameter pipe nipple. The filler necks and caps came from junked automotive power steering reservoirs. I cut the tops off of two needle valves and mounted them to the top of the tanks and made brass stems that extend to seats in the bottom of the tank. I can select which tank from the top side. The tanks are strapped to the sides of the frame on a special shoe folded over the frame tubes. They tee into a settling bowl with a shutoff. This bike runs an honest 40 and when my old friend from years ago rode it , he threw me the ultimate challenge with a twinkle. “BUT WILL IT CLIMB SHAWNEE HILL?” I returned shortly and proudly reported that I started from a dead stop at the bottom and was doing 30 at the top. The new one is the fulfillment of a fantasy I have had for years. A TRANSMISSION ! I decided I could use a Sturmey-Archer 3-speed rear wheel transmission as a jackshaft. In the planning stage, I realized the thing free-wheeled in the wrong direction but a friend on the internet asked if I could use a second jackshaft. It seemed ridiculous at first, but finally it didn’t sound all that silly. I would have to mount it on the left rear of the rectangle in a fork with the sprocket facing outward. It would have to drive a sprocket on a spindle with another sprocket which would drive the rear sprocket. I machined off the right side spoke flange and cut the center out of a 6” pulley so that it would fit against the inside of the left spoke flange. I pop-riveted it there through the spoke holes drilled 1/8”. A tapped boss was then welded to the seat post to receive a 5/8” shaft with a snap ring groove to retain the two 15-T ball- bearing sprockets on a common tubular hub. I was finally ready for a test ride. The engine is a Jiang Dong Chinese industrial engine of 5-1/2 hp. It is an angled cylinder with overhead valves and required the seat post be relocated rearward to directly against the rear fender, some 3” of relocation with a 13 X 22” rectangle plus an additional inch to make it longer. The front tube was re-formed to follow the arc of the front wheel. I have elected to leave the governor in place as it is effectively “cruise control” and I never had that before. It limits the engine to 3300 rpm, but it is enough to propel it at 42 mph. in 3rd gear. There is roughly another third of the rpm range unused. The test was sort of a shocker because the pull of the small chain loop bent the 2nd jackshaft and caused the chain to climb and jump teeth. I machined a cup that I bolted to the end of the shaft and welded an ear on it. I attached a large turnbuckle to that and the other end to a bracket bolted to the top fork behind the seat post. This is pretty much in line with the driving and driven sprockets and solved the problem, even allowing me to tweak the chain adjustment a mite. I might add, the sprockets are all #41, with the Sturmey-Archer sprocket having been machined down and inset in a recess turned in the 18-T drive sprocket and silver soldered in place. The rear wheel has a 56-T sprocket. The rear wheel is one for a Worksman industrial bicycle and has a super heavy rim with spoke nipple dimples in it and is laced with 0.100” spokes. The coaster brake sprocket is about 4”dia. With the aluminum hub and steel sprocket in place with no tire, it weighs 11-1/2 lbs.! I bought a Walmart Cruiser bike with balloon tires and a nice big tubular fork, and stainless steel fenders. I used the gooseneck, tires and tubes, fenders, fork, and put the rear coaster brake wheel on the front so I have a front brake. I am now running the rear brake chain around the rear sprocket and then connecting it’s spring to the same attachment point on the brake peddle arm. The clutch spring is off a trampoline and has lots of authority, so I am using a long motorcycle clutch lever. Of course I have the peddle to push if I want to. There is a thorn proof band inside the tires. I was lucky and found a bicycle seat about 1 foot wide. It must have been off an exercise machine. The throttle cable is a John Deere throttle and by twisting the knob it can be locked in position. One big surprise was that the transmission ratios are backward due to the fact the housing, formerly the rear wheel hub, is driven and the sprocket is the driver for the rear wheel. It makes no difference and I spend most of the time in 2nd gear to run the transmission 1:1 to spare the internals unnecessary wear. The rear fender brace that came on the donor bike was too short so I used an available piece of ½” stainless tubing that curves nicely around the outside of the fender.
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MEMORIES AND SILLY STUFF The motorbike was a way of life and a learning experience. We usually took the engines apart just to scrape carbon or just see how much wear the bearings and piston had. It didn’t take a rocket scientist to do it, but we learned by doing. One of the reasons I always wanted a transmission was because Charley Bacon came riding up one day with an 8 HP Wisconsin engine in a 20” bicycle. He had a 2-speed transmission out of a box Cushman scooter! Oh how I envied him! He burned a donut in the Mayor’s front yard and he came out storming and screaming about $600 he had put into the yard. We used to sit under the shade tree and show our MACHO by holding the spark lead and turning the flywheel as fast as we could stand it. Charley bet me I couldn’t hold his plug wire at ANY speed. That was like a double-dog dare, so I tried it cautiously. WHAM!!! I was about in orbit and Charley was rolling on the ground. That was the day I learned all about IMPULSE magnetos. It would come up on the firing point and a spring would snap it over quickly and it would shoot a fat blue spark 1”! Some of the early bikes used a Brigg & Stratton model “Y”. It had plenty of displacement but in stock trim with a tiny suction carburetor it only put out about ¾ HP. If they added a model “N” carburetor it would give about 2-1/2 HP. It must have weighed 40 Lbs. You would see them all over town doing the starting drill. They backed it off compression and lifted the rear wheel off the ground and started running, dropping the wheel and putting the arm pit over the seat horn and fanning the choke with the right hand and trying to make a deal with God. It wasn’t until recent years I learned what was so wrong with the Y’s It was the bad iron they used in the flywheel magnets. It didn’t hold magnetism well and a local shop had a device especially for re-magnetizing them. If they had only known then! I was 11 when Dad built me my first motorbike. I had traded a pretty sharp “pushmobile” he built me for an ancient Briggs & Stratton model FH. It was a real wonder, with a suction activated intake valve and a spindly 3/16” pushrod outside working a rocker arm for the exhaust. It had two flywheels like millstones and a small diameter tube running from a mixing valve on the fuel tank in the bottom of the engine all the way up to the head. It didn’t get in any hurry running but it was an ENGINE and it belonged to ME! In his true engineer fashion dad contacted the factory for parts and found it left the factory in the middle of October 1927! Someone had thrown away an old American Moto Scoot frame and I got it for $1.50 from the kid that found it. We tracked the owner down and he sold us the wheels, jackshaft, and brake band for $10 and we were in business. He put a wood floorboard on it and a simple angle iron box for a body with a top board and a seat cushion. The brake was a flat drum with a strap of metal with leather riveted to it for brake lining wrapped around it. The clutch was a jackshaft that pivoted on the axle held back with a stout spring to tension the engine belt. The final drive was chain. Dad made a clutch peddle that wiggled sideways slightly and provided a notched piece of angle iron mounted next to it I could put the peddle shaft under to hold it clutched for starting, etc. Naturally the first thing to go was the muffler. That didn’t help much as the intake valve was floating at “high” speed. I found if I stuck a screwdriver in the intake spring to make it stronger it would rev faster. This was followed by a wedge of sheet metal pivoting on one end and pulled with a “go faster” string and returned with a spring. Dad just shook his head but didn’t say much as he was wont to let me make my own mistakes on the learning curve. I also discovered that if I revved it as tight as it would go and snapped the clutch peddle out from under its catch it would either jump the front wheel about a foot in the air and/or break the drive belt. By the time I was about 13 I was ready to build my own motorbike. Dad had a Masonic brother that ran a welding shop and told him he would be glad to stick a frame together for me. I hacked up some angle iron and a bike frame and headed for the weld shop. Somehow he didn’t seem too happy to see me as it was a busy day there. I quickly laid out my crudely cut parts and showed him what I wanted. That was my first experience with “GARBAGE IN—GARBAGE OUT. It was a real misaligned piece of **** and from then on I fitted my joints to where you couldn’t blow smoke through them and wired them all together with boards and tourniquets of wire. I re-made a frame and Dad paid to have it welded up right. That was my first real practical motorbike and I was proud of it. It served me to school and back all year with no problems other than I caught my pant cuff in the drive belt and flipped the motor pulley off the shaft because I had failed to tighten it very well. It rolled under the boardwalk surrounding Phillips Petroleum Co.’s new office building construction and was history. I charged a new one to Dad and caught **** for it. When many of us got Whizzers we learned survival mechanics. They had an inserted rod that was poorly oiled and not very big. Consequently we carried a Pepsi bottle with the required amount of oil in it and a Phillips screwdriver to remove the side of the crank case and an allen wrench to remove the allen bolts on the rod cap. Also in the “kit” was a Prince Albert tobacco can and a pair of scissors to cut the can into strips to put behind the rod inserts to make it fit tighter again. If the gasket was torn beyond use, a Montgomery Ward catalog cover made a pretty good gasket. This stuff was all carried in a couple of war surplus saddle bags. Sometimes not, as occasionally the spokes would wear holes in the canvas and some of the stuff just wasn’t there. Once I was riding my 1949 Whizzer and felt something touching my leg. It was the little rod that ran all the way thru the engine the hollow camshaft turned on. I managed to push it back in without losing cam timing and peined the end of the hole with a couple of rocks to keep it in to get me home. Whizzer manufactured a “blooey pipe” to replace the flexible exhaust tube and muffler. Our next move was to stick a churn-shaped buttermilk carton on the end with friction tape to get a louder boom. We all had black mastic around the end of the pipe. That is where I learned to love buttermilk. That was the only way to get the megaphone. Back then it was REAL buttermilk and would take the skin off your tongue and stand by itself without a glass. (almost) I guess what this dissertation is all about is the sadness I feel at the passing of the era when if you wanted something badly enough you figured out a way to build it yourself. You learned a lot of life’s lessons and built self esteem by your accomplishments. I especially have fond memories of my father’s indulgence and advice IF I asked for it, and not belittling me for my failures. He was very proud of me but I had to find it out from others, as he was a very reserved man. God bless him. I grew up with the confidence that I AM D***ED GOOD AT WHAT I DO AND DON’T NEED TO PROVE ANYTHING. :cool:
Neat memories.

But that era is not entirely over and might see a new resurgence. We've reached the point that we can no longer drive cars frivolously. People will have to cobble together small engine transport of they don't want to walk or pedal or declare bankruptcy.
One of the members here has a signature line that says "If it's broke and you're broke, use weird stuff to fix it." That's always given me a laugh, but I also feel honest affection for the very idea. And our compadres here in the MB community are clearly of a similar mind.

I once knew a guy who was 95 years old about 25 years ago. He once told me that he thought that the model T was the last car that was worth a darn. His reason was that the owner could fix practically anything that might go wrong. It occured to me that those model T owners who did not live near Ford probably had no choice; there was no automotive repair industry. At least at the start.

We're in a similar spot; there are very few MB mechanics out there. But we also have modern technology that allows us to share ideas and stories, laughs, etc. Could be a golden age.
The Model T even came with a tool kit that included tooling to grind your own valve seats.