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Thread: MIni Bike frame repair

  1. #1
    Join Date
    Jul 2018
    Location
    TN
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    1,066

    MIni Bike frame repair

    Thoughts on fixing this before I start cutting and welding?

    It's a Monster Moto BW-80 frame. Been hit hard enough to bend the forks. Not sure what to do about them yet.

    I'm thinking maybe cut out both down tubes and replace them with one larger, carefully notched downtube in the center with a T brace on the bottom two.

    They're bent in such a way that cutting out the bent part and welding in new tube would be very difficult. The are warped the full length.


    I was born and raised on Venus & I may be here a while.....

  2. #2
    Join Date
    Apr 2011
    Location
    Mexico
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    8,929
    I assume the steering head isn't where it used to be? Almost everything is fixable, but that looks like a lot of work to make like new unless you have a frame jig and a mandrel tube bender on hand. I hate to be a Debbie Downer, but maybe looking for a straight frame on eBay is your best bet?

    If you're determined to fix that one, I'd bend a plate at the same angle as the bottom of the cradle to hide and reinforce the damaged radius. Then I'd either find tube that fits over the stock tube, or tube that's the same size and some smaller tube to use as backing when splicing in the new down tubes. Then weld it all up.

    As far as positioning the neck, you can try chalking out a center line from an undamaged section of the frame on a flat surface and passing a long piece of threaded rod through the steering head to act as a pointer to align it with the chalk line. Heat the tubes and put the tip of the secured threaded rod where you want it. Maybe add a couple gussets to the head if you fell you tweaked it a lot.

    You wouldn't want to trust this method at 100mph through an off camber downhill decreasing radius curve, but it might get you close on a mini-bike.
    Last edited by El Camexican; 09-19-2019 at 12:30 AM.

  3. #3
    Join Date
    Jul 2018
    Location
    TN
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    1,066
    In a wild fit, I took a section of railroad track I use for an anvil and actually got them straight. ...but now the tubing looks pretty sad. LOL.
    I'm thinking of using two pieces of sheet metal to 'box' it in. Stronger and outta sight, outta mind.

    Yes, the front end is another story. It took a HARD lick and bent the fork in severely. BUT, evenly.......I have a plan. HA!!!
    I was born and raised on Venus & I may be here a while.....

  4. #4
    Join Date
    Jul 2018
    Location
    TN
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    1,066
    Ok, the front end,,,,,bent BAD!!





    Funny thing though, both forks are perfectly even. Who ever wrecked it must've hit something dead on! LOL!!
    Even funnier....The over steer stops are centered. The only thing that orients the front end is the tabs for mounting that plastic sign plate. Cut them fuggers off and give it a flip..........and you got a raked out mini bike!!!!





    In an effort to keep them from bending more under the new stress I added some heavy wall tubing for support. Just tack (poorly) welded with a stick welder while I wait on my new gas regulator for the MIG welder.




    Bob Ross was right....No mistakes...just happy little accidents. LOL!!!!!!!















    ...
    I was born and raised on Venus & I may be here a while.....

  5. #5
    Join Date
    Jul 2018
    Location
    TN
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    1,066
    Dunno if I will or not but I am VERY tempted to get on ebay and order an axle kit and convert this to small 3 wheeler.

    Thoughts on that one?
    I was born and raised on Venus & I may be here a while.....

  6. #6
    Join Date
    Aug 2016
    Location
    East of Worcester ma
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    1,293
    Oh come on Gabriel turn it into a Skee Whee. Really never heard of one till now, a snow tracked minibike.
    Figured I’d post it here to help with ideas- hope that’s ok w/you. Click image for larger version. 

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    U get snow in Tennessee?
    Shep

  7. #7
    Join Date
    May 2006
    Location
    Not here
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    Quote Originally Posted by Shep1970 View Post
    U get snow in Tennessee?
    Shep
    I estimate that we get about 2-3" altogether annually here in southern KY and it never covers the ground for more than a couple weeks at a time tops. I live 11 minutes north of the TN state line. Every once in awhile, we have a "snowstorm" that dumps a whopping 3 1/2" inches of powder and the stores are barren of food lol. They close the local schools for 1" and sometimes less.

    I'm a south Central Hoosier native and I think it's hilarious since Indiana gets alot more snow and just deals with it but here it's so rare that everyone loses their minds when it happens.

    Gabriel lives in Ice Storm territory, though




    Sent from my Z958 using Tapatalk
    Last edited by ironchop; 10-03-2019 at 01:17 PM.

  8. #8
    Join Date
    Jul 2018
    Location
    TN
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    1,066
    Yep. Hell freezes over around here. I'll take the snow over a sheet of ice any day. Snow can be carefully driven on. Ice......An Abrams tank can't traverse a sheet of ice. Certainly not my Toyota.
    It does make for some bichin' 3 wheeler driftin' though. ....until you hit that one patch with no ice, catch traction and do the stop drop & roll.

    I remember the ice storm of '94. Still in high school. I had an ATC110 and delivered groceries and smokes all over my little town. The only time I have ever ridden my 3 wheeler on the main road with impunity. One of the local cops (jokingly) chewed me out.....then told me that he had to make his rounds in his Blazer because the squad cars were stuck in the parking lot and can't get out. Told me to be safe and thanked me for wearing a helmet. .....I was only wearing a helmet because it was too dam cold to take the wind LOL!!!
    I was born and raised on Venus & I may be here a while.....

  9. #9
    Join Date
    Aug 2016
    Location
    East of Worcester ma
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    1,293
    Gabriel, not sure where your at on this project but here’s a complete bolt on front fork conversion w/suspension for about $100. For your bike. This company had 65 sets two days ago now down to 35 or so. For the cost it doesn’t seem too bad a deal.
    https://www.gopowersports.com/minibi...bly-universal/

    Click image for larger version. 

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    Shep

  10. #10
    Join Date
    Jul 2018
    Location
    TN
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    Well, I kinda lost interest so I just got it together and moved on to another project I am more interested in......

    6.5hp Predator engine from Harbor Freight. It is about 2 steps away from being completely unrideable. I left the governor in place as well as the throttle stop. I have the throttle stop screwed all the way in and you can only get about 25% throttle. ....it will still jump out from under you. Being raked and low it won't raise the front end, it just breaks traction and jumps out from under you. I can blip the throttle and it will idle up slightly.....I have ridden it all over my field without giving it any more throttle at all. Lots of fun that way but even once you're rolling good, hitting the gas will break traction and make you crap your pants. LOL!!!! BUT, going from 80cc to 212cc will do that. Especially on a machine you can almost pick up off the ground with one hand.


    I was born and raised on Venus & I may be here a while.....

  11. #11
    Join Date
    Jun 2015
    Location
    stonecreek ohio usa
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    654
    Got room for one more if you still wanna go to haspin. That's cool!

  12. #12
    Join Date
    May 2006
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    Not here
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    Crap..... Gabriel I keep forgetting to mail your cylinder. This thread reminded me. I'll try to remember it in the next week after I get back home

    Sent from my Z958 using Tapatalk

  13. #13
    Join Date
    Jul 2018
    Location
    TN
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    Quote Originally Posted by ironchop View Post
    Crap..... Gabriel I keep forgetting to mail your cylinder. This thread reminded me. I'll try to remember it in the next week after I get back home

    Sent from my Z958 using Tapatalk
    It's no big deal. I can't see the light of day for all my projects that need finishing. LOL!
    I was born and raised on Venus & I may be here a while.....

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