Frankenstein Huffy bike won't start

Discussion in '2-Stroke Engines' started by Molotov256, Aug 30, 2010.

  1. Molotov256

    Molotov256 Member

    Hey again... I'm starting to feel like leach on this forum because I keep asking for way more advice than I'm capable of giving back. All I can really offer in return is my thanks, so thanks! :dunce:

    This is the story today:

    I've remounted a motor to my Frankenstein bike, and I can't get it to start. I've been following the sticky post in the 2-Stroke engine forum, and here's what I've been through so far.

    -Tested for spark with plug grounded to side of engine. I've got spark.
    -Dropped float bowl to check for fuel. I've got fuel.
    -Drained gas, killed some weeds with old gas, and got new gas.
    -Attempted a tow start. My neighbors are most likely organizing a petition to evict me after seeing that escapade.
    -Moved carb needle to leanest setting (I fear I may be flooding something at this point after all the failed start attempts).
    -Replaced spark plug after reading that sometimes plugs fire under test conditions but won't fire under compression.

    The engine sounds like it's got pretty good compression. I have a expansion chamber exhaust on it (not SPB style, but the big chrome banana looking kind), and when I open the throttle a bit, I get a really pingy high pitch popping noise. I think that's a good thing, like the pressure is resonating through the chamber, right?

    The only thing I can notice which seems off is the clutch... Even with the clutch disengaged, I can roll the bike more easily than other MB's I've put together. The motor turns over, but it's not as hard to turn over as before. Should I look into clutch adjustments more, or is it okay as long as it still turns the motor over?

    I'm tempted to throw this thing off a bridge into a river, but that'd even be worse for the environment than riding it, so please, guide me once again, MBc community!
    Last edited: Aug 31, 2010

  2. GearNut

    GearNut Active Member

    Grasping at straws here...... is the exhaust plugged up?
    Is the magneto rotor on backwards?
    Does the engine have good compression?
  3. Molotov256

    Molotov256 Member

    Thanks for grasping at straws with me, GearNut :cool:

    Is the exhaust plugged up? I'm pretty confident it is not.

    Is magneto rotor on backwards? I never took it off, and it used to run fine, so I don't think so.

    Does it have good compression? It sounds like it does. Is there any other way for a backyard mechanic to check compression?

    If I need to post more info, just let me know what you need to know :bowdown:
  4. Chris Crew

    Chris Crew Member

    The motor turns over, but it's not as hard to turn over as before.

    check and make sure your plug is tight in the hole
    check and make sure your manifolds and head are properly tight
    (I farted around with my second bike for nearly a week before I realized that I had only given the plug a few turns with my fingers and never put the wrench on it--once I tightened it up, happy motoring.)
  5. GearNut

    GearNut Active Member

    Follow ChrisCrew's lead first.

    To check compression properly requires a compression tester, a gauge with a hose and spark plug hole adapter.
    To test it the shade tree way, remove the spark plug, keeping it connected to the spark plug wire. Tape the spark plug to the head so it still will ground out on the cylinder head fins. This will protect the CDI box when the engine it turned over.

    Hold your thumb quite firmly over the spark plug hole. You are trying to seal off the hole here.
    This part is easiest with somebody's help: turn the engine over by rotating the rear wheel. (be sure the clutch is locked up). You should not be able to keep your thumb on the spark plug hole tight enough to prevent the compression from leaking past it.

    If you do not have any compression, remove the cylinder head and check for a blown head gasket.
  6. motorpsycho

    motorpsycho Active Member

    you have fuel in the bowl, but that doesn't mean that it's getting into the cylinder.
    give it a shot of starting fluid in the back of the carb and try to start it.
    if it fires, then you have a fuel problem....gas not getting into the cylinder.
    also check your wiring to make sure that no bare wires are touching anything steel.
    this will ground out the ignition system.
    you have spark, but sometimes the spark is not strong enough to fire the gas..i know,it sounds funny bit it's true. a shorted or grounded wire, broken connector or loose connector can cause this. get rid of the push together connectors on the wires and solder them together. those connectors are junk and will give you nothing but headaches.
  7. Molotov256

    Molotov256 Member

    Chris Crew hit the nail on the head! Upon further investigation, I noticed a bit of oil dripping off the top front of the engine from the head gasket seam. I remember now that I had changed the head gasket on this motor last season, and the replacement gasket was a metal one. Not knowing any better, i had just put the bare metal gasket in thinking that was how it worked. I guess it held for a little while, but eventually it wore out and I started leaking air through the bad seal.

    I took off the head, cleaned and copper-coated the gasket, and put it all back together, and it fired right up and runs like a champ. Yea! :D

    Thanks for the shade tree compression test how-to, Gearnut, and sound advice about soldering wires, Psycho.

    Thanks a lot for the suggestions everybody - it's so easy to overlook things when you've been pulling your hair out.
    Last edited: Aug 31, 2010
  8. GearNut

    GearNut Active Member

    Congratulations on your repair!
  9. Chris Crew

    Chris Crew Member you need to know