Carburetor won't fit under frame

Discussion in 'Instructions for Building and Repairing Motorized ' started by Zeeb, May 5, 2018.

  1. Zeeb

    Zeeb New Member

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    Hi everyone;
    I managed to fit the engine within the bicycle frame, but clearance between engine and frame cross bar isn't adequate to fit the carburetor.
    I have made an offset intake tube to allow the carburetor to sit outside the bike frame (see attached pictures).
    I used a 45 degree copper pipe elbow and a 1/2" piece of copper straight pipe to re-position the carburetor. The pipe pieces are held together with small segments of vinyl hose, held tightly to the copper via hose clamps.

    I tried unsuccessfully to get the engine to start, but haven't done any troubleshooting yet.

    I'm wondering if anyone else has had this problem, and if there's a better intake solution. I'm concerned that my current intake tube is so long that fuel will not stay atomized in the air long enough to reach the engine.

    Even after hitting the primer till gas dripped from the air filter, I couldn't get the engine to kick over.

    Thanks!
     

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  2. Greg58

    Greg58 Well-Known Member

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    Some new engines are hard to start, first make sure its firing by removing the spark plug and reattaching the the plug wire and ground the plug to the head, then roll the bike or spin the rear wheel so the engine turns over. You should see the plug fire, if not check your wiring. If you have fire check the plug after trying to start it, you should see fuel residue on the plug.
     
  3. AZPhil

    AZPhil New Member

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    Greg is right about the spark. I bought a new A50 kit on line and when we installed it, The bike would not start. I had plenty of fuel but no spark
    The Magneto I got with the kit was bad and I had to buy another one and its running great now!

    Semper Fi
    Phil
     
  4. Chaz

    Chaz Active Member

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    There are offset intakes you can buy from most of our sponsor dealers. If that indeed is the problem but it doesn't look crazy long, just make sure you have no air leak at the connections.

    There's no need to use the primer and you seem to be flooding.

    Also there's no need to use the factory suggested 16:1 fuel/oil ratio. It's way too heavy. You can go directly to 32:1
     
  5. Zeeb

    Zeeb New Member

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    Thanks for the input everyone! Chaz, you were right; I was flooding. The engine is now running with the homemade air intake. It isn't perfect (minor carb tuning is likely needed), but runs strong enough to maintain my confidence in the intake setup I have.
     
  6. Tyler6357

    Tyler6357 Active Member

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  7. Chaz

    Chaz Active Member

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    Good that you got her going. I wouldn't get too fussy about fine tuning until you've broken her in. It will begin to run stronger as the rings seat. Time to start racking up the miles. Also note that your chain will stretch as it settles in so keep an eye on that.
     
  8. Zeeb

    Zeeb New Member

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    Right on; chain is my biggest concern now. Despite my efforts, the rear sprocket still has some up-down play; likely less than 1/32", as i cannot measure the play with tape measure. It's only visible if I concentrate on the sprocket while spinning the rear wheel, but does still seem to cause the typical tight-loose-tight oscillation in the chain.
    It feels smooth enough as I roll the bike that I'm inclined to test ride it as is; just can't be 100% certain it won't cause a problem at some point.
     
  9. Tyler6357

    Tyler6357 Active Member

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    I use a clam shell sprocket adapter but even with that I can't get the wobble out 100%. Also, the chain should be slightly loose, that is, it should have some slack in it. There are people who are really good at setting up a rag joint set up but I'm not one of them.
     
  10. Zeeb

    Zeeb New Member

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    Lol neither am I.
    ive just heard that rag joint setups tend to eventually involve broken spokes. spokes are designed to take force linearly, not to take side loading.
    hence why i avoided the rag joint setup
     
  11. Tyler6357

    Tyler6357 Active Member

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    I agree, I think the rag joint set up is horrible. Most bicycle spokes are not designed for engine torque. If you've got a sprocket adapter then you shouldn't have too much trouble. Just make sure you leave some slack in the chain and test it so that it's not hitting any part of engine or tire, it will bounce a bit under normal operation.
     
  12. Zeeb

    Zeeb New Member

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