Carburetor Manifold

Discussion in 'Frame Mounted Engines' started by motor puzzle, Sep 11, 2007.

  1. motor puzzle

    motor puzzle Guest


    I finally got my engine in but the carburator won't fit because it hits the frame of the bike. (See picture below). My plan is to angle/twist the carburator manifold a few dedrees away from the frame. Not sure exactly how to go about this, but have a couple of ideas.

    I) I will mount the manifold to a sturdy surface. With a propane torch heat up the manifold around the bend. I found another piece of tube that fits in perfectly over the end of the manifold (the end that attaches to the carb) to use as a tool in bending it (leverage). After heating up the manifold, I would slide this tube in over the end of the manifold to apply pressure in the direction I want it to bend. I only have to bend/twist the manifold about a quarter of an inch or less. If the bending does not happen easily, I will not force it because I don't want to destroy the manifold.

    2) Use copper pipes and solder. I have a piece of copper pipe that would slide nicely into the end of the manifold and a 45 degree angle that would put the carb out of the way. Maybe too much heat for solder?

    I appreciate any suggestions/comments.


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    Last edited by a moderator: Sep 11, 2007

  2. azbill

    azbill Active Member

    the engine produces too much heat for solder (it will melt) could braze the copper if necessary
    is your manifold chrome or silver ?
    chrome are steel and should be bendable with heat
    silver are cast and won't be bendable
  3. motor puzzle

    motor puzzle Guest

    Thanks Bill. It's the silver. :(

    Does anyone know where to find one of the chrome (steel) manifolds?

    Would it be possible to braze the cast aluminum manifold and copper pipe together? Does it depend on the filler metal. I found the below:

    It is difficult to braze or weld aluminum to copper, because of the low melting temperature (1018 F) of the aluminum-copper eutectic and its extreme brittleness. By heating and cooling rapidly, however, reasonably ductile joints are made for applications such as copper inserts in aluminum castings. The usual filler metals and fluxes for brazing aluminum to aluminum can be used, or the silver alloy filler metals BAg-1 and BAg-la can be used if heating and cooling are rapid (to minimize diffusion). Pretinning the copper surfaces with solder or silver alloy filler metal improves wetting and permits shorter time at brazing temperature. A more practical way to braze aluminum to copper is to braze one end of a short length of aluminum-coated steel tube to the aluminum, and then silver braze the other

  4. drimpact

    drimpact Member

  5. motor puzzle

    motor puzzle Guest

    Thanks. Lots of goodies there.....
  6. gauge

    gauge Guest

    i say bend it out words on the side of ure choice
  7. Would cutting the manifold mess it up in any way if it gives the carby enough room to work?
  8. srdavo

    srdavo Active Member

    from your pic, it looks like your engine could slide forward enough to allow room for your carb. is your mounting bracket attached by U-bolts?

    when you start bending intake tubes, you could create less air flow.
  9. motor puzzle

    motor puzzle Guest

    Steel manifod: bent

    Large Filipino, no matter how I cut it, it wouldn't have worked.

    SRDAVO, if I were to push the engine forward it would have to be about 4 or 5 inches. Since I was using a u bolt, I would've had to use really long screws to get the engine to move up that distance and I was concerned that there would be too much play or too much a chance of things bending do to torque (Please see my thread on General discussion:My Spoiler Project). Plus, I tried pedaling with the engine pushed up a few inches and it was not as comfortable. I just needed to bend the manifold just a bit so I'm hoping that it doesn't cause too many airflow problems.

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  10. Donny G

    Donny G Guest

    My intake manifold was hand fabricated from scratch (so was the rest of the project) it took about 45 minutes

    I used a pair of handlebars from an old schwinn varsity
    the flanges were free hand drawn and cut out of 3/16" plate on a metal cutting band saw welds are TIG

    on a side note like metals are used to build manifolds either aluminum or steel
    I can't imagine using copper or brass, or trying to weld different materials together my advice is get some tubing (old handlebars work well!)

    here's a pic note the updraft cement mixer carb

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    Last edited by a moderator: Sep 27, 2007