The vibrations are KILLING me

Discussion in 'Motorized Bicycle General Discussion' started by Basement Cat, Jul 24, 2011.

  1. Basement Cat

    Basement Cat New Member

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    Hey guys,

    I just finished my first MB build using a 60cc China HT engine. It runs just fine but I'm getting these unbearable vibrations in my hands the faster I go. It's so bad that anything above 1/2 throttle hurts my hands really badly.

    I've tried putting sand in the handlebars to weigh them down and I have one of those olde stems with rubber bushings that are supposed to dampen vibrations but this isn't enough. I've tried searching the forums but I'm having difficulty finding the information that I need.

    Any help would be greatly appreciated!

    PS: My top speed is 30 mph with the stock sprockets on the 60cc engine, is that what I should be expecting form this engine?
     
  2. jburr36

    jburr36 Member

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    Get some motorbike gloves with gell on the palms. Those HT motors are notorious for vibration.
     
  3. The_Aleman

    The_Aleman New Member

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    Make sure the mounts are sitting flat against the frame and the muffler is also clamped to the frame.
    Also, you might want to get a smaller rear sprocket. That way you'll be turning less RPM at 25-30MPH.
    I recommend a 36T. These engines make nice power at 4000-5000RPM. Gear yourself accordingly!
     
  4. msrfan

    msrfan Active Member

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    Check my thread ''no more vibrations, almost''.
     
  5. sportscarpat

    sportscarpat Bonneville Bomber the Salt Flat record breaker

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    From my experience excess vibration is often caused by misalignment of the chain and sprockets. Stand behind the bike and look from the rear sprocket up to the engine sprocket. Look for deflection in the chain. Also, make sure your engine is not rotated to the left or right of frame centerline.
     
  6. Al.Fisherman

    Al.Fisherman New Member

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    My first build was as you described. I mounted my engine as it is supposed to be mounted. Sprocket was perfect. Chain no problem. Then one day I cracked the frame and had to switch frames....no more vibration.
     
  7. PerryP180

    PerryP180 New Member

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    Make sure the motor mounts are snug. I wound up putting some inner-tube around the bike frame at the mounts. Surprisingly this made a significant difference. Make sure the front tire isn't flattened in a spot also.
     
  8. Goat Herder

    Goat Herder Gutter Rider

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    Make sure the muffler is mounted securely. Just hanging off the jug is not enough IMO . A surprising amount of vibs can come from a vibrating muffler.
     
  9. Basement Cat

    Basement Cat New Member

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    What's a good way to mount the muffler besides just relying on the jug?
     
  10. Goat Herder

    Goat Herder Gutter Rider

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    You could use a perfect size muffler clamp to match your bikes tubing. Custom bend some flat stock band steel [​IMG] wrap around the muffler to reach the muffler clamp.

    You could even tack weld part of this fastening arrangement to the muffler. Thing is all of this is a matched effort . The motor will need to be mounted solid. You could slot your holes in the muffler clamp down to muffler pipe junction set up a little.

    Most all of these kits come with a little band clap for the muffler to fasten to the down tube. Granted it is a cheesy one it still can make a difference are you using it?
     
  11. Basement Cat

    Basement Cat New Member

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    I feel like such a noob but I don't know how to use it with my frame. I'll post pictures of how I set up my engine kit tomorrow when the sun's out. I might have set something up wrong... :(

    Also, I popped open the clutch side cover and the flathead bolts that goes on the little gear was completely loosened. Could this have been causing my problem?

    I feel so stupid; I've been building and porting 2 strokes for 5 years and I can't even get this bicycle engine kit right, lol. I'm really hoping that I don't have to balance the crank...
     
  12. biknut

    biknut Active Member

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    #12 biknut, Jul 25, 2011
    Last edited: Jul 25, 2011
  13. DuctTapedGoat

    DuctTapedGoat Active Member

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    Getting a new exhaust made a world of difference for myself - both my banana pipe and the SBP pipe.
     
  14. The_Aleman

    The_Aleman New Member

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    Well, the point is the chinagirls aren't exactly balanced or blueprinted lol...I've had 5 of em, and they all danced a little different.
    When you spin an engine 6000RPM, the crankshaft is spinning over 100x a second! Think about that!
    Any imperfections in balance will be magnified of course, so if you get an engine that's off, really, what can ya do but lower the revs?

    I have kind of a built-in rev-limiter myself..I don't really like spinning my engines over that 6K mark.
    None of my 2-strokes liked it either. With my 34T, they purred happily.
    My 4-stroke does 30MPH at 6K RPM, and it makes maximum HP at 34 :D
     
  15. Basement Cat

    Basement Cat New Member

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    I didn't realize these engines were built to rev so low. Some of my Go-Ped engines easily rev up to 18k under load and the lowest revving engine I've built went up to 12-12.5k, lol. I suppose I'll just go slower for now :(
     
  16. Basement Cat

    Basement Cat New Member

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    I've got a picture of my setup, does it look right?

    [​IMG]


    Also, the crankcase is leaking fuel/oil. Has anyone else had this issue?
     
  17. KDB

    KDB New Member

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    I made motor mounts out of my old rubber handlegrips. appear to help some.

    It looks just like mine, not that that means anything. My first build too and less than two weeks on the road.

    Some experenced person please answer. I have this same problem and appear to be leaking more than I burn.
     
  18. PerryP180

    PerryP180 New Member

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    You have the NT carb in the photo. I had what I thought was fuel leaking from the engine. After many hours of searching I found the leak to actually be on the nipple where the fuel line connects to the carb. The nipple is so close to the carb wall that I couldn't get the black fuel lines to seat properly. The walls of the fuel line are too thick. I've gone back to a clear fuel line (has thinner walls), used a small zip tie to clamp it and I've had no problem. I also put the sip ties on all points where the fuel line is over a nipple. (fuel filter and petcock) The clear line works but it does expand in heat and it will get brittle in a few months and need replacing. As for engine vibration, sound like the mounts aren't tight enough. Also remember that the smaller the bike frame the worse the vibration will be. I tried a small framed mountain bike and the vibration was significant. I now use larger frame cruisers and have very little.
     
  19. Dan

    Dan Staff
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    All great advise and just to add, Harbor freight has these great ridding gloves meant for jack-hammering. Well padded on the palms and finger less. Like 8 bucks or some thing. The fingerless part is great to in that you can do adjustments with out taking em off. Called "Vibrato" or some thing like that.

    Also a great help is a bent or lay back seat post so your not ridding on you feet and hands. Makes a huge difference. With the engine doing the work, no need to have your weight so far forward and over the pedals. Might want cruiser handle bars with em though.
     
  20. biknut

    biknut Active Member

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    All single cylinder motors vibrate like paint shakers at certain rpm. All you can accomplish by balancing your motor is to change the rpm where it vibrates the most. It's impossible to balance for all speeds. For cruising around on a MB the trick is to gear your bike tall enough to not be running in it's worst vibration zone when you get it up to battle speed.

    China Girls aren't racers, so they're not balanced to be smooth near red line. Mine all feel smoothest closer to maximum torque.
     

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