Cracked Frame - Two Stroke Motorized Bike

Discussion in 'Frame Mounted Engines' started by Leroybrown420, Jul 10, 2015.

  1. Leroybrown420

    Leroybrown420 Member

    I sold my Critical cycle today to a local MB'er who actually cracked his frame just below the front engine mount. I wish I'd taken a photos but was to busy counting the benjamins. This was a first for me. The bike was a kit bike that he bought locally and apparently has had nothing but problems since day 1. The photos are from Craigslist where he original purchased the bike. Has anyone ever cracked their frame? I'm leaking towards installation error but should we be worried about our frames splitting in half? He did mention that he jumped a few curbs. However, I currently have a MB that once upon a time had a 62 tooth rear sprocket (see last photo) that I have wheeled the hell out of and used off-road for a few fishing adventures & trail riding. It now has a 32 tooth sprocket since I moved to the city but my frame shows no sign of stress cracks or anything unusual. Weird.

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  2. Timbone

    Timbone Active Member

    Bike frames crack even when used as intended. If the steel frame cracks, there are several things one can do to fix and even improve the frame.
     
  3. Leroybrown420

    Leroybrown420 Member

    Nothing last forever, and everything is fixable. However, I'll will never own a Sikk bike (unless it's free) after seeing a snapped steel frame with a stock 48cc and rider who weighs around 120lbs. My very fist motorized bike is still running around NAU. I actually road the that bike until the chain snapped and the tires were bald, then motorized it. I bet the frame just fine.

    My 1st MB
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  4. HeadSmess

    HeadSmess Well-Known Member

    dont trust old frames with brazed joints, dont trust alloy, dont trust anything cheap and nasty...

    best one for me has still been a tig welded cromo shogun...
     
  5. wheelbender6

    wheelbender6 Well-Known Member

    Sorry you broke a frame, but I sure love your pics with the red rocks in the background. Most of the cracked frames I have heard of lately were cruiser frames with the welded-on cargo racks, like the Panama Jack.
     
  6. tekstep01

    tekstep01 Member

    i broke a schwinn frame right behind the seat on the downtubes
     
  7. Dailybiker88

    Dailybiker88 Guest

    I've cracked almost every frame I've owned and put a motor on I'm convinced it is the combo of rough roads and lack of suspension as well as vibration
     
  8. Timbone

    Timbone Active Member

    Me, too! Every frame I have used has endured some kind of major failure.
     
  9. butre

    butre Well-Known Member

    lug brazed is fine in my experience.
     
  10. Frankenstein

    Frankenstein Well-Known Member

    True, but that is significantly different than a non-lugged frame structurally speaking.
     
  11. Crisco

    Crisco Member

    Wow... You either need to start buying better frames or learning how to assemble properly before you eat a big chunk of dirt... Nom...
     
  12. Timbone

    Timbone Active Member

    Geez, what a bunch of attitudes to be found here.

    Bike number one was a Walmart quality steel frame with 700C wheels and minimal chain clearance. Ocaasional whipping of the 415 chain ate a big hole in the seat stay.

    Upon inspection after the frame was retired, the motor mount u bolt on the seatpost had produced a large crack.

    Frame #2 was one of those cheap aluminum GT-2A frames that got online for about $140. The motormount pedestal failed very quickly, teaching me a lot about the importance of proper motor mounting. The terminal blow to that frame was a cracked weld connecting the downtube to the headtube/ frame tank area.

    Most recent frame failure was a complete crack of the rear left chainstay on my OCC Chopper Bike frame. I have welded that back and its strong now, but there's more than a hint of warp.
     
  13. Sgt. Howard

    Sgt. Howard Member

    I have a flotilla of Huffy frames that are still quite serviceable after six years- except the Panama Jacks. They always break where the rack is welded to the down tube- and on the down tube at that.
     
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