Whizzer motor kits were added to thousands of bicycles.  You could cruise along with the motor or pedal along to help the motor.  Most Whizzers were pedal started, meaning you got the engine going with pedal power. There was a compression release lever on the handlebars that was held open before you started.  The compression lever propped the exhaust valve open.  Once you got pedaling fast enough, you shut the compression release and the motor started.  Whizzer Motor Company started in 1939 as Breene-Taylor Engineering.  Whizzer is supposedly borrowed from Bryon "Whizzer" White of the University of Colorado, who went on to play for the Pittsburgh Pirates and Detroit Lions and went on to become a member of the US Supreme Court.  In late 1939 the Whizzer kit known as the Model D were sold for $54.95.   The engine was a not very durable, air-cooled, four-cylinder, 8.45 c.i.d. engine developing 1 3/8" horsepower.  Bore and stroke were an over square 2 1/4" x 2 1/8" which remained a constant in all Whizzer motors.  It featured a two-piece split crankcase, roller main and rod bearings, pressure lubrication, counter-weighted drop forged steel crankshaft and connecting rod and a 6.5:1 compression ratio.  Breene-Taylor apparently made the small side-draft carburetor in house.  The carb mounted to a swivel-jointed intake manifold which allowed the carb float to sit level on different bicycle frames.  The engine and drivetrain clamped onto the bike frame with a three-point mount, which stayed basically the same throughout all the models.  The early drive system was by rollers are V-belt.  The belt forced the bottom rear roller against the rear tires.  There was no clutch or transmission but the drive could be tensioned via a cable that mounted to the tank. 

The 1940 Model E engine used an aluminum head and added a dipstick to check the engine oil level.  The E had caged roller bearing, an improved Breene-Taylor carb, improved magneto ignition, hotter camshaft as well as a few other improvements.  The Model D was estimated at 300 units sold and the Model E at 1500 units.  During the war, Whizzers were available to only people involved in defense work.  In 1943 Whizzer introduced the "New Model" which was the F, for wartime service.  The New Model made 2 1/2 horsepower and replaced the roller drive with belt drive.  This include a clutch of sorts.  A lever released or engaged the drive pulley.  The large pulley bolted to the spokes of the wheel with small clamps.  This was the drive system that Whizzer used until the end.  After the New Model came the Model F with a larger motorcycle-type fuel tank (1.2 gallon).  The Model F sold just over 4,000 units.   The Model H engine was introduced in the summer of 1946.   The Model H replaced the split crankcase with a one-piece casting cum side cover.   The crankshaft used roller bearings at one end and big ball bearing on the other, with insert rod bearings. Seals and tappets were much more reliable and the lubrication was by splash and spray  and the Tillotson carb replaced the earlier unit.  The exhaust pipe curved forward and around instead of straight back.  The H used a different Whizzer logo fuel tank decal, H serial number and twist off gas cap.   Reliability and performance were much improved. 

The 1947 H motor kit retailed for $89.50 to $97.55 and they sold nearly 139,000 between March 1946 and May 1948.  Whizzer teamed with the Cleveland Welding Company to produce 1,000 Whizzer Pacemaker motorbikes.  The cantilever frame used by Cleveland Welding was clearly a patent infringement of the Schwinn frame.  To placate Schwinn, Whizzer pulled production for Cleveland Welding and gave it to Schwinn.  To produce a frame for the Whizzer motor, Schwinn took their heavy duty frame and made a few minor changes.   They notched the rear fender and frame for belt clearance, added thicker spokes, heavier coils in the spring fork and installed a front rim brake.  These were sold as complete bikes through Schwinn dealers and were designated "WZ" models.   The first Schwinn WZ came out in 1947.  Schwinn also modified a Schwinn Cycle truck delivery bike into the "Powercycle truck" bikes.  In May 1948 Whizzer released the Model J.   The biggest changes included a handlebar twist grip and debossed fuel tank.   The Whizzers had previously used thumb controls for the throttle and compression release.  The new twist grips made the Whizzer more like a motorcycle.  They also used more chrome on the J and a new Carter carburetor, although later models used the Tillotson carb again.  Whizzer also produced a line of accessories including chrome fuel tank, centrifugal clutch, echo exhaust pipe, spring fork, hi-lo beam headlight, saddle bags, buddy seat, speedometer and bumperettes.  In 1948 Whizzer introduced the Pacemaker.  The complete bike included a telescopic front fork, 24" wheels, dual beam headlight, taillight, generator and front drum brake for $199.50.   The Pacemaker started in 1948 with the J motor.  By late 1949, so the upgraded 300 series motor was introduced.  The 300 (helped in design by Vince Piggins, father of the Z-28 Camaro) was basically a tweaked J with bigger valves, higher compression, more efficient combustion chamber, better cooling and smoother manifolding.  The result was three horsepower and claimed top speed of 40 mph. 

In 1950 the Sportsman was added.  The Sportsman had a heavy duty Schwinn chassis with 20" wheels.  It was too low for pedals so it used foot pegs instead.  The 300 S (Sportsman)  motor gained kick starting, two speed Bi-Matic transmission with centrifugal clutch, and a 6 volt AC generator.  A built in clutch engaged as you applied the throttle, and at 15 mph, theoretically, you let off the gas momentarily and the transmission shifted into high.  The Bi-Matic was hard to adjust, temperamental and had a tendency to fling out the lubricant and burn bearings.  The Bi-Matic was discontinued in 1951. After the 300 engine came the 500/600/600S and 700 series.  These were similar to the 300 but used a heavier casting in the kick starter area, except the 700 which did not use the kick starter.   By 1952, Whizzer had saturated the market and sales plummeted.  The Whizzers had become "uncool" and felt competition from motor scooters and cheap used cars. 

In 1951 Whizzer offered the Ambassador, based on there own frame design/  The Ambassador had a Whizzer spring fork, kick starting, foot pegs, most of the Sportsman's equipment, and the 600S motor.  It retailed for $249.50.  Whizzer had sold approximately 15,600 Series 300/300S engines, 2,300 Series 500, 1,500 Series 600 and 5,300 Series 700 engines.   At one time, Whizzer considered a Stingray based model but it never made it past the prototype stage.  Towards the end of production many kits were made out of whatever parts were left over.  This makes it difficult to identify some of the later models.

 

Most of this information was distilled from the Jan/Feb 1996 Classic Bike by Steve and Lynn Culver.