Is it normal for engine to turn bicycle pedal around?

Discussion in '2-Stroke Engines' started by John-Forrest, Sep 20, 2008.

  1. John-Forrest

    John-Forrest Member

    I just went on a long trip and there were a lot of lot steep hills. Somewhere along the way, the pedal and pedal arm starting acting like it was coming loose. I went to a bike shop; the guy told me the bike part seems fine but there may be loose bearings in the engine sprocket. Anyway, now the engine is making the bicycle sprocket fly around. I have to hold my feet on the pedals to keep it from flying around at the same speed the engine is turning. Every rotation there is some kind of weird knock.

    I'm definitely feeling nervous to ride this like this. Sometimes bike pedal flies around VERY HARD! Like it could break an ankle bone or something. I have to stand on pedal to keep it from moving around.

    Anyone have any idea what might be happening? Could have anything to do with clutch not completely disengaging bicycle sprocket/chain?


    HERPER Member

    do you have a coaster break? because if so my bike had the same thing. the bearings inside the coaster broke and jammed the brakes/wouldnt work after time.
    i then fixed it with new parts and it did it again..

    i learned that i needed to add a new tire with freewheel. and added a front and rear break
  3. Esteban

    Esteban Active Member

  4. John-Forrest

    John-Forrest Member

    What is a coaster brake?

    I'm not sure what a coaster brake is. This particular bike, a WildFire MB26 (preassembled), came with brake pads on rear tire and disc brake on front. Coaster brakes are those old bikes where you brake by turning wheel back, right?
  5. Skyliner70cc

    Skyliner70cc Active Member

    Sounds like bad freewheel or cassette.
  6. You will need to rebuild the Rear Hub and bearings on the bicycle.
    I would advise NOT to use the bike until this is fixed.
    Its not worth the possible Hospital bills.


  7. arceeguy

    arceeguy Active Member

    And I wouldn't go back to that bike shop again for repairs. That was a major mis-diagnosis!
  8. JemmaUK

    JemmaUK Guest

    It sounds like the bearing in the hub has collapsed which means the ball bearings are acting very much like a partially engaged clutch to the pedals... not a good place to be in.

    I wouldnt, as has been said, ride it under power although riding with the clutch in should be ok.. its likely you'll need the wheel relaced to new hub and cassette..

    Was the bike new when you fitted the motor up to it? or was it an old bike?

    Jemma xx
  9. sparky

    sparky Active Member

    The symptoms sound similar to what I've got. A clicking noise when I pedal, and if you pedal while standing up... the crank slips. Doesn't sound exactly the same as my problems, but I'm with Skyliner... it's your freewheel/cassette!!
  10. John-Forrest

    John-Forrest Member

    I'm a little confused about the terminology here. I don't have coaster brakes. I'm don't know what a "casette", "hub", or "freewheel" is. (Might be worth considering making a glossary for this forum.) The bicycle and engine are all brand new (well, a few months anyway).

    I did go for a local trip today and condition was definitely getting worse - I certainly won't take it out on the road again until I have some idea what is going on here. One thing that is strange is despite this tug-of-war between the bike sprocket/crank/pedal system and what the engine is doing, neither chain has snapped. Also this has just started happening; it wasn't happening orginally.

    Upon thinking it over, I think the bike pedal/crank/sprocket system is jammed, and I may have to replace that. One fellow who pulled over to help me when I was out of my area thought something was wrong with ball bearings. Pedal resists going backwards. I checked riding my own regular bicycle (nonmotorized), can pedal backwards and just hold pedal while going downhill. (This may be why coaster brake doesn't work, it can't go backwards.)

    Also, I have another thread here about aligning bicycle chain with engine chain. Bicycle chain is too tight/ engine chain tends to be loose. I wonder if that has something to do with this. Since I got this bike, I've had the impression two chain systems seem to compete with one another. This may be a major bug with current motorized bike assemblies.

    I'm not very good with mechanical stuff and have a hard time finding mechanic who can handle this. Bike stores seem to have a prejudice against gas engines and motorcycle shops tend to be contemptuous of motorized bicycles (and don't know about the bicycle parts). That's part of the reason I joined this forum.
  11. sparky

    sparky Active Member

    If you can pedal backwards, you have a freewheel or a cassette (multiple sprockets on a freewheel for multi-speed bikes).

    The problem has something to do with the pedaling chain, right?? If so, the problem is most likely not in the crank, so it's gotta be in the freewheel or cassette. Replace that, and you'll prolly be golden. Just try and pedal with the engine off and listen where the noise is coming from? Does the freewheel sometimes not let you pedal backwards easily?
  12. fetor56

    fetor56 Guest

  13. John-Forrest

    John-Forrest Member

    Crankset is jammed!

    "Does the freewheel sometimes not let you pedal backwards easily?"

    Actually, I cannot pedal backwards at all, or with tremendous effort. Freewheel means you can hold pedal to rest, while the bike is rolling downhill, right? I think that's stuck, must be some ball bearings that popped out in there. So because whole crankset is frozen, engine is pulling the pedals around at its own speed (which is pretty dangerous!).

    Hopefully, this is a standard part for bicycles, and I don't have to order it specifically made for WildFire Motors.

    I think what must be happening is because engine tends to give out on steep inclines, I put unusual stress on bicycle crankset to pedal it (while engine is spinning at a different speed).

    If I continue with this bike, I'll probably wind up putting a 70cc engine on so I don't have to use pedal to get up steep inclines.

    Now, if I can only find a bike shop that is willing to fix this... otherwise, I'll have to do it myself. Is this a common problem for these kind of bikes?
  14. Ghost0

    Ghost0 Guest

    Just take the rear wheel off and head to the bike shop and they can fix the rear cassette. Then there is no motor for them to be suspicious about. If they ask what the other sprocket is just say it is to run a lighting generator or something.
  15. sparky

    sparky Active Member

  16. John-Forrest

    John-Forrest Member

    I did manage to get to tech support at WildFire Motors and man said the same thing as you people - take rear wheel off and fix freewheel part. I was surprised to find it is in rear tire, for some reason, I was stuck on idea that it was inside crankset system.

    The main problem with bike shops is in this state MA, it's against insurance regs to take gas engine bicycles inside their shops. They told me they will work on it as long as it's a bicyle problem; they don't want to deal with engines.
  17. duivendyk

    duivendyk Guest

    Go to where you can educate yourself ,the site is a treasure trove of bicycle lore
    Last edited by a moderator: Sep 23, 2008
  18. John-Forrest

    John-Forrest Member

    Hello, I would like to report that the freewheel is ok now. This is kind of embarrassing, but all this guy in this bike shop did was put some lubricant on the freewheel, and it coasts/backpedals fine now. In any case, I know a lot more about how this thing works now.

    I still think my bike chain and engine chain are out of sync with one another. I need to make engine chain shorter so bike chain isn't so tight.

    Anyway, it runs ok now. Thanks for all your help and advice. I hope this info is useful to others with a similar problem.
  19. duivendyk

    duivendyk Guest

    Read Sheldon Brown, you'll learn a lot !