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  1. #1
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    250cc Rugged Mountain Bike Build (street legal)

    Hello everyone,

    I wanted to start this post because I planned on starting this awesome project where I'm going to build a 250cc, 4-stroke, street legal mountain bike. I already have a mongoose, which would have been most of the cost, that will be used as the frame.

    I'm currently in the registration and certification process, which I will pass for sure , but will be able to simultaneously work on the bike itself.

    I not building from scratch as most of the parts will be assembled: frame, engine + transmission, etc. It mostly going to be bolting, welding, and positioning on my part; bolting on intake and exhaust, hooking up radiator if water cooled, fuel lines and brake lines, the easy stuff.

    The whole purpose is to build the ultimate street and off-road mountain bike/motorcycle anyone has ever seen. This is a daring, but completely obtainable, project that will be documented and broadcasted on youtube, facebook, ustream, and my personal website for all the enthusiasts out there to see.

    From start to finish, frame to cold start, viewers would watch as a seemingly limited mountain bike is transformed into a rugged, off-road capable, street legal, 250cc, 4-stroke, super/ultra octane fueled, dual-suspension, tactical, all-purpose bike!

    I know there are a lot of the kilowatt electric bikes out there that even corporations are starting to pick up on via grants, some of which I heard can it 115mph?!

    I wanted to do this because it will be very fuel-efficient since the engine will be single cylinder and 4-stroke. It will have a multi-gear transmission so that it can go faster and still be efficient.

    I also think this project will do very well because people don't always get to see in-depth videos of some of the awesome projects people take part in. Not everyone gets to see how a car is built from start to finish, has a server is set up, how the "K" supercomputer was built, etc. So, that's why I plan to document.

    What thoughts and suggestions would you all have about this project and being able to see it from frame to cold start?

    Now that I think about it, I might buy a Mongoose Status frame.

    Thanks,

  2. #2
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    Here's a picture of the bike and an engine similar to what I want to use.
    Attached Thumbnails Attached Thumbnails 250cc Rugged Mountain Bike Build (street legal)-file0003.jpg  

    250cc Rugged Mountain Bike Build (street legal)-file0007.jpg  


  3. #3
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    I would not trust that bike under human power, let alone with a 250cc.

    Edit: To make this a bit more constructive; if you want to do something like this you would be far better starting from scratch as far as the frame is concerned. Post in the frame building section of the forum. Also, don't underestimate how much power a 250cc can put out, start with something smaller like a 50cc or electric.

  4. #4
    What could go wrong ...
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    that frame can barely handle pedal power so be sure and post a video of the first time you fire it up and the frame explodes ... I really want to see that
    I used to ride to Win ... Now I ride to Grin

    While my guitar gently weeps, my bike sits there mocking me

  5. #5
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    Quote Originally Posted by Zoke2 View Post
    that frame can barely handle pedal power so be sure and post a video of the first time you fire it up and the frame explodes ... I really want to see that
    Quote Originally Posted by cerebroside View Post
    I would not trust that bike under human power, let alone with a 250cc.

    Edit: To make this a bit more constructive; if you want to do something like this you would be far better starting from scratch as far as the frame is concerned. Post in the frame building section of the forum. Also, don't underestimate how much power a 250cc can put out, start with something smaller like a 50cc or electric.
    Believe me, I'm planning this whole project out from exact length of tubing, mount points, chain guards, etc. I'm not some excited average Joe who wants to do something crazy without researching first.

    What I provided in my first post was just to touch base.

    I know about the frame and that's why I planned on reinforcing with with a few steel square tubes and using mostly welds instead of bolts and clamps like most gas/motorized bicycle kits out there.

    But, if you all really advise trying another frame or simply starting from scratch with the frame, I'm all ears!

    cerebroside: I have first hand experience with a 250cc on both a dirt bike and quad/4-wheeler. The reason I chose a 250 instead of a 150 or 100 is because I need the torque for multiple gears.

  6. #6
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    Quote Originally Posted by Liu Kang View Post
    You want to put a 250cc 4 stroke engine on a cheap Wal Mart bicycle?

    Are you trying to troll or something?
    The bike in the picture was the initial bike I though about using. But as you can see in my first post near the end I stated that I would most likely change frames.

    Also I just posted about how I would reinforce the frame I chose with steel square tubes.

  7. #7
    I work in .001 tolerances
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    A couple of boys I went to school with built this for their grad project.
    Done right and done well
    Project M85 - Ultralight Freeride MotorCycle

  8. #8
    What could go wrong ...
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    Quote Originally Posted by macb6497 View Post
    Also I just posted about how I would reinforce the frame I chose with steel square tubes.
    exactly how do you plan to use steel tubes with an aluminum frame ... why not build a steel frame to begin with ... something like this
    Attached Thumbnails Attached Thumbnails 250cc Rugged Mountain Bike Build (street legal)-really-big-wheels.jpg  

    I used to ride to Win ... Now I ride to Grin

    While my guitar gently weeps, my bike sits there mocking me

  9. #9
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    Quote Originally Posted by macb6497 View Post
    ...

    But, if you all really advise trying another frame or simply starting from scratch with the frame, I'm all ears!
    The way a motorbike engine of that size mounts to the frame is going to be seriously incompatible with any pushbike frame without pretty much rebuilding it.

    If you really want to do this, have a look at some motorbike frames and CAD up something, then think about how you are going to accomplish building it. Do you have experience/equipment for MIG/TIG or oxy? I hear that silver brazing is the best for starting out, but people in the frame building forum would know more (so ask there).

  10. #10
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    Quote Originally Posted by Liu Kang View Post

    You're going to have to spend a lot of money on very good bike components to POSSIBLY make your project work.

    I stated I would take advise on whether or not to use a custom frame.

    If I build the frame from scratch then that solves most of the problems.

    I thought about using an already made frame for simplicity.

  11. #11
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    Quote Originally Posted by cerebroside View Post
    The way a motorbike engine of that size mounts to the frame is going to be seriously incompatible with any pushbike frame without pretty much rebuilding it.
    I see then that I must make the frame myself.

    Aluminum would be sufficient as a frame but if the manufacturer doesn't make the frame strong enough then too bad, i'll have to do it myself.

  12. #12
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    steel can't be welded to aluminum.
    the engine pictured, which is from what looks to be a 4x4 quad is WAY to big, and Way overkill for what you are wanting to accomplish.
    the honda crf 250r (water cooled) or crf 230f (air cooled) would be best options for the engines.
    most mountain bike trails are not open to motorized powered vehicles so why not just buy an older street plated dirtbike? thats what i did, i paid 1700 for a street legal 1996 honda xr600r, and love it for around town and out on the trails. i also have a crf250r for the track, and i have my mountain bike. not a single bone in my body wants to blend the 2 bikes, they are totally different.
    what state do you live in? how do you know you will "for sure" get it registered street legal?
    Juice

  13. #13
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    Juice

  14. #14
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    Quote Originally Posted by Der Juicen View Post
    steel can't be welded to aluminum.
    the engine pictured, which is from what looks to be a 4x4 quad is WAY to big, and Way overkill for what you are wanting to accomplish.
    the honda crf 250r (water cooled) or crf 230f (air cooled) would be best options for the engines.
    most mountain bike trails are not open to motorized powered vehicles so why not just buy an older street plated dirtbike? thats what i did, i paid 1700 for a street legal 1996 honda xr600r, and love it for around town and out on the trails. i also have a crf250r for the track, and i have my mountain bike. not a single bone in my body wants to blend the 2 bikes, they are totally different.
    what state do you live in? how do you know you will "for sure" get it registered street legal?
    A bi-metallic strip would have been used.

    The engine in the picture was just an example as it was attached to my 4-wheeler.

    Also, you're right on spot as to what engine I wanted to use and why. The crf is a great bike with lots of power.

    I also did a quick search and found these:

    Street Legal Requirements at DMV.org: The DMV Made Simple

    http://www.wsp.wa.gov/traveler/docs/...motorcycle.pdf

    But like you said, I can never be 100% sure I'll get approved.

  15. #15
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    Yeah, this is where I got the notion that an electric bike could go 115mph in my first post

    "Electric motorcycles can hit speeds of 150mph,"

  16. #16
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    Quote Originally Posted by Liu Kang View Post
    So it looks like the OP wants to build a motorcycle instead of a bicycle. You're in the wrong forum friend.

    Thumpertalk.com is just down the road. Bye bye.
    I've been on thumpertalk to talk about my android ATV trail locator app, but it isn't as lively...

  17. #17
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    if this is something you REALLY NEED TO DO FOR THE HELL OF IT, get your legal paperwork figured out with the state first. then pick the components you are going to use, then start from scratch with cad drawings to build from. and build either an all aluminum frame, or use all chromoly.
    do it right the first time and dont kill yourself.
    Juice

  18. #18
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    Not to seem arrogant, but this project really isn't difficult.

    If you step back and look at what I would need, excluding costs, it wouldn't seem unreachable.

    There are 2500 hp cars using aluminum and carbon fiber

    For the frame, what would really be needed?: Square tubes of different lengths from discountsteel.com, for starters, TIG welder or acetylene torch with RG-45 steel rod, a couple drill bits, grinder, band saw. And that would be it for the most part.

  19. #19
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    i know its more involved than you make it seem for it to be safe.
    if you really know what you are doing you wouldnt have posted such a shitty bike as a frame example to start with, and you would have found a picture of what you really plan to use for the motor, not just go take a picture of one twice the size just because it was in your garage.
    Juice

  20. #20
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    I love it... Just make sure you video the maiden voyage for us...
    I ride faster than I should...

  21. #21
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    I once joined a Corvette forum to talk about Mustangs, I got banned.
    I also joined a pro gun forum to talk about banning guns, I was banned too.
    Then I joined a mountain bike forum to talk about building a dirtbike.......

  22. #22
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    Quote Originally Posted by Der Juicen View Post
    i know its more involved than you make it seem for it to be safe.
    if you really know what you are doing you wouldnt have posted such a shitty bike as a frame example to start with, and you would have found a picture of what you really plan to use for the motor, not just go take a picture of one twice the size just because it was in your garage.
    Just because I don't dedicate my life to worrying about how other companies produce their product doesn't mean I don't know what I'm taking about.

    I don't care how they make their bikes because I know how strong aluminum can be.

    You may be forced to follow standards because you really don't understand how things work, but I don't.

    People like me who understand things on a more in-depth level don't need to know some useless 5-point delta config because I understand the forces involved with machinery being I can calculate it when I need to, not open a text book to see how others have done it.

    I can reinforce the frame in whatever way I need. YOU may have to abide by manufacturer specs, but because I understand I can manipulate things to my needs.

    There are many ways to reinforce a frame, you just don't have experience.

  23. #23
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    Quote Originally Posted by the-one1 View Post
    I once joined a Corvette forum to talk about Mustangs, I got banned.
    I also joined a pro gun forum to talk about banning guns, I was banned too.
    Then I joined a mountain bike forum to talk about building a dirtbike.......
    Well, that sucks. But, you're off topic.

  24. #24
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    I'll build it and worry about forces on my own time seeing that most of you all are chained to standards.

    Here's a tip for the ones who deny: get an understand and stop following and listening to others.

    This project would seem simple to you, if you understood.

    I can see that most are stuck up; that's why you can never say you're trying to be nice.

    I guess being arrogant is necessary.

  25. #25
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    Quote Originally Posted by Liu Kang View Post
    Look who's talking.

    You obviously have NO experience if you were thinking of welding steel to aluminum. If you knew anything of what you were talking about you would know that steel can not be properly welded to aluminum.

    Look through my previous posts for "bi-metallic". You'll understand. And don't even respond with "you need thicker gauge". Ever heard of do-it-yourself?


    Like I said in my previous post, I'll do it myself. Most of you are chained to standards and are unable to work around things.

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