Chain Tensioner Chain Tensioner Woes

Discussion in 'Transmission / Drivetrain' started by Unirocket, Jun 2, 2012.

  1. Unirocket

    Unirocket New Member

    Hey all,

    Well - just when I hit 170 miles on my new 66cc HT engine, the chain tensioner decided to take a turn on me, my wheel, my spokes, my tire, and ultimately my bike.

    Surely there must be a better design...
     

    Attached Files:


  2. 2stroker

    2stroker Banned

    Ya its called a bumblebeebolton. Lol..I dont personally care for chain drivin kits and this is why. To much to break. Keep it simple!!! theres a couple other friction kits out there if ya google em im sure you will see they are more reliable.
     
  3. 2stroker

    2stroker Banned

    http://www.kingsmotorbikes.com/bike_motor_engine_idler_pulley.html
    is this the one you have or is it stronger? I found it on another post. It might be a little tougher.
     
  4. tooljunkie

    tooljunkie Member

    this kind of carnage i can deal with,its the broken casting behind the chain drive gear that bothers me.split case and take to work for aluminum welding.
    i hope its weld-able.
    sorry to see it happen to anybody.
    next project will be spring loaded tensioner.i suspect needing to build at least 3 before i come up with something satisfactory.
     
    Last edited: Jun 3, 2012
  5. 2stroker

    2stroker Banned


    Sounds like project time! Woohoo!
     
  6. tooljunkie

    tooljunkie Member

    well i put on my spare engine,stuck a roller skate wheel in the lathe and cut a chain groove into it,that stuff is tough,while turning it i made a ring like a rubber band,i couldnt break it.
    mounted it in the bracket,lined up the chain and tagged it to the frame with my welder.
    its NOT moving.
    will spring load my other bike when i get casting welded and start my new build.
     
  7. 2stroker

    2stroker Banned

    I have a old vintage bike bug that uses a skate board wheel. The roller skater wheel should work good how deep is the chain groove? My vintage grips good with out the grooves. Let me know how that works out for ya. If it works good i might do that to my skate board wheel. Having a lathe is always a good thing!
     
  8. Unirocket

    Unirocket New Member

    What you probably can't see from the picture is that the frame is also bent... Time for a new bike just because of a poor chain tensioner design.
     
  9. tooljunkie

    tooljunkie Member

    i saw the bow in the lower rail.depending what its made of steel,aluminum-its possible it could be straightened,but if it cracks its junk.at leas as far as a motor goes.
    i will be sticking to all steel frames,i have no fear welding with my mig.steel plate for brackets is easy to come by to make any necessary brackets.

    2stroker-i cut the groove pretty much the same depth as the original one.
    the bearings are pretty much the same as the stock tensioner.they pop out easy for greasing,and there are two bearings,not like the single bearing on the stock one.
     
  10. Lunardog

    Lunardog Member

    That skate wheel is a nice idea. If one cut the grove deep enough, once nice and tight the chain would have room to stretch without fear of jumping off the tensioner.Definately post on how well it holds up please. And 2stroker, your not allowed to say bumbleleebolton for at least a week! lol
     
  11. Unirocket

    Unirocket New Member

    After about 3-4 hours spent on sawing, drilling and grinding, I have come up with a new tensioner on a new bike. Let's hope this one holds out...
     

    Attached Files:

  12. Steve1990

    Steve1990 New Member

    HA! so I'm not the only one who's bike has decided to do that. When mine did it, it ripped 1/2 the spokes out of the wheel, but didn't really damage the tensioner or bike frame too much. When I got the wheel back together, it tried to do it again. This time I noticed it wouldn't sit tight no matter what I did so I drilled a hole thru both halves of the chain tensioner bracket and the chain-stay on the frame and used a piece of the broken spoke as a pin to pin it all together. Its really quite solid, about as solid as I think its going to ever be without welding.

    (Ignore the bits of inner tube in the bracket, they were their to help keep it still while I drilled, never bothered to take them out)
     

    Attached Files:

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