The new Whizzer: making it go!

By Ron Dow

 

 

          My goal was to build a machine that would beat Kenny Thomas and his 64.2 mph monster.  After several months and several dollars, I’m about ready to concede.  However, just in case anyone is curious, I’ll share some of the details on what was done during this effort.

 

It must be noted that any changes undertaken may violate EPA noise and emission standards as well as void the manufacturer’s warranty. That said, here we go!

 

          The new Whizzer engine certainly has potential.  Contrary to what Whizzer specifications state, the displacement is identical to that of the vintage motor. It sports a stout bottom end and able to withstand the stress of 8,500 rpm. Additionally, there is room in the cylinder for significant valve enlargement.  It incorporates a fixed timing CD ignition whose “firing point” can readily be changed from its factory set position. The ignition system is totally separate from other motor electricals and will function satisfactorily to approximately 6,200 rpm.

 

          The new Whizzer claims 25 mph as delivered.  Simply removing the intake restrictor and exhaust baffle bumps the speed to the mid or upper 30 mph range.  Beyond that speed, the motor needs removal for more serious work. As modified below, the bike will run all day long at 50+ mph.

 

             Figure I shows the upper cylinder.  Stock valves are ~0.875” diameter (22mm).  There is sufficient room to enlarge the intake valve to 1.156” (30mm) and the exhaust to 1.056” (27mm).  To minimize machine work, valves from a Toyota (quad valve) were selected. They have the correct stem diameter; however, they require head rework and a groove cut to accommodate the valve spring keeper clip. Stock valve springs should be shimmed ~ 1/8” or replaced with more stout items. The cylinder head requires machining to clear the oversize valves and must be milled to maintain the compression ratio (Fig. II).  After loosing several head gaskets, I opted to install “Helicoil” inserts for ALL nine headbolts and eliminate the pair of original long studs, which pass through the head and thread into the crankcase.  See Fig. VII. The cylinder now attaches to the crankcase with four studs like the vintage engine. Torque to 150 inch-pounds using grade-8 or stainless steel bolts.

 

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                            Fig. I                                                                  Fig. II

 

Intake and exhaust ports were cleaned up for improved airflow but left nearly stock in diameter (Fig. III-IV) A wedged-shaped spacer was installed under the exhaust elbow (Fig. V) and the interior of the elbow recontoured in an effort to reduce the ninety-degree exhaust gas angle.  

 

                                                  

          

                               Fig. III                                                                       Fig. IV  

 

 

 

 

 

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                         Fig. V                                                                             Fig. VI

 

 

          It’s an easy task to advance the timing by drilling and tapping an additional hole forward of the stock position on the flywheel. (Fig. VI) Note: Unlike the vintage motor, the flywheel bolt has right-hand threads. I went from 14 degrees (stock) to 23 degrees BTDC.  If an owner decides to make a timing change, I urge that they do not simply lengthen the “trigger plate”.   At 6,000 rpm, centrifugal force may cause the extended plate to lift just enough to strike and destroy the trigger pickup coil.  I can vouch to that!

 

          If you intend to operate the engine much beyond 6,000 RPM, be aware that many of the early CDI ignition modules had a built-in rev-limiter. Bypassing this feature is a bit time consuming but can be successfully accomplished with patience.  I will submit a separate article on how to accomplish this, if there is interest.

 

          Cylinder head overheating is a problem.  After the initial modifications, including a reground camshaft, cylinder head temperature approached 625 degrees F.  Ideally this should be 450-475 degrees F.   Painting the cylinder black helped, reducing the temperature to ~ 605 degrees.  The biggest improvement came when a copper head gasket replaced the stock steel item (Fig. VII).  This dropped the temperature to ~525 degrees.  Still some work to do in this area.

 

 

 

 

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                              Fig. VII                                                          Fig. VIII

 

The early “new generation” Whizzer engines had a problem with oil purging from the crankcase.  The factory has remedied the situation but not for an engine turning 6,000+ rpm.  I enlarged the interior vent passages in the crankcase and replaced the stock vent components with a Cushman crankcase breather (p/n 875938)…...thanks to some experimentation by Jim Petitti of Raceway Services, Salem, OR (Fig. VIII).  A hose from the breather routes the oil away from the belts and rear tire. A supplementary vent was added to the lifter cover (Fig. IX).  Access to the interior passages requires separating the crankcase halves.  New gaskets are inexpensive.

                      

 

                             Fig. IX                                                              Fig. X

 

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                          Fig. XI                                                              Fig. XI I                                                          

 

          Two 3/32” holes were drilled through the crankcase, adjacent to the lifters. This provides oil to the lifters and valve stems while providing an additional escape path for crankcase blow-by gasses  (Fig X).  An easier, but less effective approach is to cut the cylinder base gasket as shown in figure XI.

       

          I experimented with mushroom-based titanium lifters (0.50” diameter mushroom) with a net result of a crankcase full of ground up titanium (Fig. XII).

 

                       

          A  1-1/2” extension was added between the stock intake flange and the carburetor.  Both a Tillotson and Carter were tried (21/32” and 23/32” venturi respectively) and  provide similar performance.

 

 

                                                                 

Camshafts are the product of Raceway Services. Stock lift is ~0.150”.  Raceway increased this to 0.196”.  Valve lash is reduced from 0.012” (stock) to 0.006’ (intake) and 0.008” (exhaust).

 

       

 

         The engine is mounted on a 1949 Schwinn Springer. Best speed, thus far, is 61 mph

         with the bike secured on a calibrated chassis dynamometer. Jerry Lane, Morrow, OH                                                                                  

 

          

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manufacturers an automatic clutch (a/c) for the new engine. It makes driving    the bike an absolute dream and has performed flawlessly despite the estimated  7-8 hp output.

 

                                                Fig. XIV        Early (very) test bike

 

A word of caution regarding the automatic clutch (a/c).  Pulley spacing on the new Whizzer is greater than that of the vintage pulley.  The modified a/c is  therefore heavier than the vintage a/c. This places considerable stress on the clutch-arm and associated components. The new Whizzer manual clutch arm is attached via a bolt passing through two, 12 mm steel bushings, which are pressed into the crankcase.  The bolt provides for a sloppy fit allowing the arm to move excessively. Please consider that you are replacing a one-pound

 

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pulley assembly with a four- pound centrifugal clutch.  Loose fitting parts are subject to vibration and vibration can lead to a broken clutch arm (several times!), cracked crankcase (once), or parts imbedded in your leg (Yup, that too).

 

Consider trashing the new Whizzer clutch-arm mounting scheme in favor of the vintage approach.  Replace the steel bushings with a vintage Whizzer 1/2” bronze bushing and a precision 1/2” shaft threaded into the clutch arm. The vintage bushing is not a snug fit, therefore applying Loctite is recommended.  Modifying the a/c moves the input pulley approximately 1/2” farther out.   Tension from the front belt puts considerable stress on the arm and attaching parts.  I suggest high-pressure grease be applied to the shaft and bushing prior to assembly.  Replacing the forged, cast-iron clutch arm with a steel unit is cheap insurance.

 

               A simple plate attached to the stock belt-guard bosses (secure with 12-24 flathead screws) allows the use of the vintage Whizzer belt guard (Fig. XV- XVI). The stock guard is plastic. It provides superior rider protection by covering the entire flywheel. However, the plastic guard is subject to cracking at the mounting holes from engine vibration when modified to clear the a/c.

 

                             Fig. XV                                                     Fig. XVI

 

 

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