Vintage hot rod Whizzer

Discussion in 'Whizzer Motorized Bicycles' started by Quenton Guenther, Jan 31, 2009.

  1. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    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,
    Last edited by a moderator: Dec 15, 2015

  2. KilroyCD

    KilroyCD Active Member

    I've just shorted out my keyboard with my drool pool... :drool5::drool5::drool5:
  3. RdKryton

    RdKryton Active Member

    What kind of compression ratio are you shooting for? I'm curious as to how you are going to have the piston extend .030 into the head. Are you changing the connecting rod, is the 700 cylinder shorter, or is the Clinton piston a little taller? Are you going to need special lifters for the Weber cam? I would love to hear this thing run when it's finished.

  4. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Looking for 175 lbs. of compression. Rod is stock. Piston is slightly taller from the wrist pin, however the top has a beveled edge. I also reduced the base of the cylinder to arrive at the desired height. The vintage motor has .500" base lifters, so will work perfectly with the Weber camshaft. When I start it you should be able to hear it in PA from here, LOL.
    I will try to take a few pictures along the way.

    Have fun,
  5. WZ507

    WZ507 Member

    That late style cylinder with the large ports and valves should really breath some life into that thing. The original "H" cylinder would severely limit the engine's potential due to the little pee holes it has for ports.
    Last edited by a moderator: Dec 15, 2015
  6. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    I decided to use an "H" cylinder to make sure everything will fit. Bore was ok and left a fair amount of metal after the 2.415 hole. It looks like the intake valve is about as large as I want go without getting too close the exhaust valve. I could have used a 26 MM metric valve, but gain was only .0236, so I went with the 1", and like the idea of a little space between the valves.

    Now that I know everything will fit, it is time to transfer all the parts to a #2151 cylinder.

    Hope no one thinks I ruined a "H" cylinder during my tests. The "H" cylinder was already beyond using a .060" piston, and had been repaired on the top. From the looks of my test "H" cylinder I would say it had carried a lot of people for a lot of miles before ending up on my work bench.

    I am somewhat undecided on the final piston design, after working with the pistons , one is completely flat on the top, and the other now has a beveled edge. I can test the beveled version first, however if I bore it to fit the flat piston, I can't return to the beveled piston. One is +.005, and the other is +.020.

    have fun,

    Attached Files:

  7. I can't wait to see your results. My next build is with the 300 series wich is basiclly the same as the 700 jug you are using. I decided to use the 300 I have over the H & J motors I have sitting on the shelf due to the larger valves & exhaust port & as you said they have more room for modification. I just got a high fin head with no broken fins, that was a feat in itself. The head on the engine now has just about every fin broken. Good luck & can't wait to see your results. Dan