Where to purchase oversized piston

Discussion in 'Whizzer Motorized Bicycles' started by BlueWhizzer, Apr 9, 2013.

  1. BlueWhizzer

    BlueWhizzer Member

    Well i pulled the engine off my Whizzer. A friend of mine is helping me rebuild the engine (builds drag race and airplane engines) and it has a burnt valve and also the piston needs to be replaced. Where is a good place to get an over sized piston? Also, is .030 over the largest piston that is made as a direct fit?

  2. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Pistons WERE available in sizes up to .060" for the vintage Whizzers, however they are very rare and hard to find. Many companies are offering the new edition piston as a replacement and can be made to work.

    The new edition piston isn't as tall from the wrist pin to the top of the piston, and therefore it doesn't end up level at the top of the stroke.
    It is about .125" below the top of the cylinder, however it is the same in the new edition motors.

    The biggest difference is in the wrist pin size, as the new edition pin has a smaller O.D. The vintage pin is 9/16", whereas the new edition is 14 MM, a diffeence of .0113188976377953". A few are supplying the new edition piston with a new rod bushing, however I found using an adjustable reamer and increasing the wrist pin holes in the piston to accept the vintage wrist pin is much easier, faster, and just better.

    The short piston height can be modifed in several ways if necessary to make the piston even wth the top of the cylinder. One way is to use gasket sealer at the base and eliminate the base gasket, another is to remove some of the cylinder height by milling off part of the base.

    The new edition pistons only come in .25, .50, .75, and 1.0. Don't assume it is in inches, as it is metric. The first O.S. is .25 of 1 MM or .0098" [approx .010" O.S.], second is .50 of 1 MM, or .19685 [approx .020" O.S.], third is .75 of 1 MM or .029527" [approx. .030"], and last is 1.0 of 1 MM or .39370078" [approx .040"].

    One important issue to consider is the rings are much better on the new edition pistons, and the new edition pistons are currently available.

    Check with Mike at Wizzer Works in Ohio, or Wildfire also in Ohio if you elect to use the new edition piston.

    Have fun,
    BlueWhizzer likes this.
  3. BlueWhizzer

    BlueWhizzer Member

    Thank You very much for all the info Quenton. I sent all of this info to my engine builder friend.

    I am surprised at how hard it is to replace the piston on an old original engine. I guess there isn't a large enough demand to warrant someone making a hundred or so of the correct pistons to sell.
  4. BlueWhizzer

    BlueWhizzer Member

    My (engine builder) friend knurled the piston and says the original piston could work ok if we could get .010 over rings for it...anybody know if .010 over rings are available for the stock piston?

    Or if the ring set for the new edition pistons would fit an original piston?

    Quenton, he thought your idea of reaming the new edition piston to fit the original wrist pin in it was a good solution, if we have to go that route. Thank You very much for your help.
  5. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Memorylane Classics in Ohio has the vintage rings in several sizes. You can also check with Chuck Gatto in IL.

    Several companies have made replacement pistons for the vintage Whizzers including Jahns racing pistons.

    If you elect to knurl the piston, be sure to polish the skirt directly under the wrist pin on each side to avoid exessive oil build up on the piston.

    Let me know if you can't find the .010" rings.

    Have fun,
  6. BlueWhizzer

    BlueWhizzer Member

    Thanks again Quenton I'll contact them and see if they have them.
  7. mason_man

    mason_man Active Member

    Jahn's hasn't made a piston in 4,5 years, rings are still available.
    are you still looking for pistons BlueWhizzer?
    i didn't know the Korean pistons came in metric, thanks for the info.

  8. BlueWhizzer

    BlueWhizzer Member

    Ray, my engine builder wants me to hold off buying anything for a few days until he decides what we should do, He is redoing the head of a Honda VTEC engine and it is time consuming.
  9. BlueWhizzer

    BlueWhizzer Member

    Well, .010 over ring set is on the way thanks to Chuck Gatto gwhizers2@cs.com Should have it running soon for the nice weather.