I know several members of this site are in the process of putting together "vintage" motorbikes using the legendary "H" motor. Isn't it amazing that a 60-year-old motor can still get the job done? I am excited for them because I know the power band is going to surprise them. The original motors have a lot more low-end torque, and leaving the stop sign will be a lot easier than they expect. Whizzer supplied America with approx. 139,000 "H" motors in the mid to late '40s.
Many have asked me to "light the fire" on the original motors, but I usually declined because so many experts are around with decades of knowledge on the American Whizzer.
Guess What? I agreed to try a little of my magic on an "H" motor to compete this year in a few of the upcoming Whizzer events in the mid west. I am hoping this motor will deliver for its owner.
I will keep track of this project and share the results, if anyone is interested.
So far I replaced the "H" cylinder with a "700" cylinder, because the "700" has more metal around the exhaust port to allow for a little more modification. I will be installing a specially modified .030" O.S. Clinton piston with a bore of 2.415", which will contribute two additional features. One feature will be more cubic inches, the upgraded motor will increase 1.2847 cubic inches, from the 8.449 cubic inch original to 9.7337 cubic inches, but my favorite is making the motor more over square. Over square motors will usually rev a little higher.
Next I installed a German made needle-bearing crankshaft. The pin has been welded on both sides to make sure it doesn't twist. I replaced both crankshaft bearings with NOS parts, including the Torrington needle bearing in the side cover. Installed a new crankshaft seal, the correct crankshaft spacers, and replaced the points with an electronic ignition module. The owner supplied me with a really nice "Weber" camshaft to complete the bottom end of the motor.
In my quest to increase the intake valve size, I had to consider the limits imposed by the close exhaust valve. I decided to leave the exhaust valve at 7/8" to allow me to maximize the intake valve to 1" without running out of space.
The motor will sport a Mikuni carburetor fed through an aluminum manifold to help supply the larger intake valve.
Next project will be re-working the high fin head to accept the top of the piston. I plan to have the very top of the piston exceed the top of the cylinder by .030" and will recess the head to add the needed clearances.
End of part one.
Have fun,
Many have asked me to "light the fire" on the original motors, but I usually declined because so many experts are around with decades of knowledge on the American Whizzer.
Guess What? I agreed to try a little of my magic on an "H" motor to compete this year in a few of the upcoming Whizzer events in the mid west. I am hoping this motor will deliver for its owner.
I will keep track of this project and share the results, if anyone is interested.
So far I replaced the "H" cylinder with a "700" cylinder, because the "700" has more metal around the exhaust port to allow for a little more modification. I will be installing a specially modified .030" O.S. Clinton piston with a bore of 2.415", which will contribute two additional features. One feature will be more cubic inches, the upgraded motor will increase 1.2847 cubic inches, from the 8.449 cubic inch original to 9.7337 cubic inches, but my favorite is making the motor more over square. Over square motors will usually rev a little higher.
Next I installed a German made needle-bearing crankshaft. The pin has been welded on both sides to make sure it doesn't twist. I replaced both crankshaft bearings with NOS parts, including the Torrington needle bearing in the side cover. Installed a new crankshaft seal, the correct crankshaft spacers, and replaced the points with an electronic ignition module. The owner supplied me with a really nice "Weber" camshaft to complete the bottom end of the motor.
In my quest to increase the intake valve size, I had to consider the limits imposed by the close exhaust valve. I decided to leave the exhaust valve at 7/8" to allow me to maximize the intake valve to 1" without running out of space.
The motor will sport a Mikuni carburetor fed through an aluminum manifold to help supply the larger intake valve.
Next project will be re-working the high fin head to accept the top of the piston. I plan to have the very top of the piston exceed the top of the cylinder by .030" and will recess the head to add the needed clearances.
End of part one.
Have fun,
Last edited by a moderator:
