not realy a mini bike

[builder bob]

so i'm trying to build a low to the ground gas 2 weel vehicle. i know it's not a mini bike but i'm going to try and build a low bike so... i got a 50cc 4 cycle honda copy engine that i'm still breaking in. 2.5 hp. i don't know how to weld and have to fix my school's welder before i can learn but i will get this bike done! what kind of pipe do you recommend for a bike project? the whole bike will be stretched and dropped about a foot. this is a picture of kind of what i want the frame to be like

 

[cumminsbayou4x4]

that has a cafe racer look

 

[builder bob]

ya i guess it does. i wish i could use a bigger engine but i can't because of the laws in my state. any way i can get a little more power out of the engine without a large amount of machining? i won't be able to do any machining for at least a year but i can do anything else.

 

[mckutzy]

Cool Idea, i have seen that pic before...

I recently have completed my bike(check my sig line), and there is a few things to think of first. The start... You have an Idea(that pic) and you have a motor(also good)
Do you plan to make this a street legal ride or just something to bomb around "off road"
(this is one of the big questions about this project, You may get more or less on a streetable ride, as opposed to just a mini chopper which you will get help)

What kinda skills and tools do ya have.
What amount of space do you have.

With your basic idea down, what kind of tires/wheels do you have/plan to use.

What kinda "transmission" Ie. a TC or centrifugal clutch.

For me I had to choose on what side for the drive chain. A jackshaft was needed and required a design and method of intergration with the frame.

Off hand these are just a few things I had to think of during the design and early building phase.
With no prior knowledge of how to weld, this will be a difficult process to begin this project. You dont want to kill yourself on the first go from it breaking apart.

I do however wish you good luck in this build, but I have to let you know a few things about this before starting.

 

[builder bob]

thanks, definitely tell me whatever because i've never built anything like this. i want my bike to be street legal (that's why i got a 50cc engine) and will be getting a DOT full face helmet sometime. i also had to get an engine with a centrifugal clutch to be able to legalize the bike. i have a lot of wood working tools, a metal lathe that is not set up yet, 3 drill press, and a couple angle grinders. my school has a broken MIG and regular stick welders, i think i spoted a tube bender, and a small metal lathe that no one there rely knows how to use (exept me! ), a car lift, more angle grinders, ability to use pneumatic tools, and also the engineering teacher lets me use everything there. i have read a lot about welding but it kind of freaks me out (scared of light that could make me go blind)and that's why i've never learned. but now i will! i have a big shop that has a lot of tools and i can clean out my work spot to be able to bring in up to a car sized thing. i build alot of stuff out of wood so i'm good at that and am decent at machining unless i need to eat something which causes me to be unable to do math. i want some 26" fat near slick bike tires which i found on ebay awhile ago. i'm probably going to ditch the pedals so i can get a disk break in the back. i rely like the bike your working on! the fat back tire is awesome! i'm worried about the strength of my welds to so what i could do is build some simple clutch less weedy powered mini bike with breaks and a kill switch on the engine then drive it fast into a speed bump. or make a small cart, put a couple sinder blocks in it, use some of my r/c airplane stuff to control it and drive it into the speed bump. the second one is probably better.
sorry this was long and disorginized!

 

[mckutzy]

OK, a DOT build will most likely need the tires/rims,brakes(front/rear check your state regs), lights(front/stop)signals(im sure, but check your state regs) to be DOT(once again check your state regs)


I am not to up to date on American regs, but you may have to get some special licensing for your frame and have an inspection, like a custom motorcycle. Up here we call it a Ubuild. A one off frame/motorcycle.

So a big part of this is going to be up to what your state regs say you can do an how you can do it.

Also what kinda budget do have to do this, if i may ask? Looks like it will cost a few $$.

 

[builder bob]

I actually don't need to do anything complicated to make it street legal. Bike breaks and tires are fine and it can have pedals (classifying it as a gas bike) or it can have no pedals and be classified as a moped. Both ways I would get a sticker from the registration place to put on the bike. It has to be 50 cc or under though and that's why I got the engine that I got. I also need a DOT helmet and a driving permit but that's it. There isn't even an inspection, i just have to fill out a form and make up a number for the bike and I'm all set!

I will spend up to the price of a small new gokart but the more it costs the slower it'll get done.

 

[mckutzy]

What about lights, it isnt all that easy to have a reliable power source to hook up for having lights, on that motor of yours.

 

[builder bob]

lights are not required but i want them. there is no where on the engine to connect anything to generate power because of how the clutch and gearing are bolted to the engine block. what i was thinking of doing was just getting a 12 volt lion and wiring it up.

i finally found the maximum speed for my engine. 7,800= red line, 10,000= busted aluminum connecting rod (everything else is steel). funny thing is, the vidio i watch where the guy blew the rod his engine sounded like it was going so much faster then mine does and i revved it to full when i took it out of the box.

i can not find the mix screws on the carb even though i saw a picture of where they should be.

 

[builder bob]

alright here's the big question, do i try and enlarge the gap in the frame of a smallish bike (not adult size) and use that as a starting place for the bike or buy a bike that's already big enough and cut it?

 

[mckutzy]

I think a bigger question is how are you joining parts after they are cut, no welder and experiance kinda puts a damper on things.

 

[builder bob]

i can get them welded at a shop if i have to but the cost rely adds up

 

[builder bob]

is it possible to use a regular arc welder to build it without burning through the pipe or changing the strength of the metal? the engineering teacher at my school is convinced that it's impossible. if so i can build this soon. how bout for welding a muffler, what do i need?

 

[mckutzy]

Your going to need a MIG or Flux cored "MIG". Stick for the most part isnt going to do it without being a bad mess.

 

[builder bob]

Ok I guess I've definitly got to fix my school's MIG welder then

 

[builder bob]

would a spot welder be good to use on a muffler?

 

[mckutzy]

Spot welder is made for joining sheet metal. Cars are a good example, except they have alot of molded sheets welded together.

I would suggest...
You can get a cheap 120v FC wirefeed from harbor freight for not that much. That would be a good start for practice and getting you started. They all have a "sweet spot", they have a setting some where with the feed and the given heat setting that welds optimally.
These cant really weld sheet metal or thin thin tube well or at all(your millage may very).
They are kinda rough, they are temperamental machines and a bit to get used to, but they can deliver a lesson or 2 of you are willing to hack it. Mainly keeping your speed/motion consistant when you find "the sweet spot", and Keeping your work clean from debris from the previous weld or on the start.

I have a older clarke 90e, 90amp 120v. It has a setting that i dont change any more and it can weld up to 1/8. I dont push it cause I know the limits of my machine. I(and typically these machines) need a full clean 120v with 15amp circuit to run with out interruption. Nothing worse that striking an arc and the whole line goes dead cause of overloading the circuit.

 

[builder bob]

Spot welder is made for joining sheet metal. Cars are a good example, except they have alot of molded sheets welded together.

ya mufflers are made with a lot of thin metal so would one work?

I would suggest...
You can get a cheap 120v FC wirefeed from harbor freight for not that much. That would be a good start for practice and getting you started. They all have a "sweet spot", they have a setting some where with the feed and the given heat setting that welds optimally.
These cant really weld sheet metal or thin thin tube well or at all(your millage may very).
They are kinda rough, they are temperamental machines and a bit to get used to, but they can deliver a lesson or 2 of you are willing to hack it. Mainly keeping your speed/motion consistant when you find "the sweet spot", and Keeping your work clean from debris from the previous weld or on the start.

so something like this? http://www.harborfreight.com/welding/mig-flux-welders/170-amp-migflux-wire-welder-22-volts-110-amps-68885.html

 

[mckutzy]

Spot welders in automotive industry make the muffler itself, not the joining of the exaust system. Thats what I was trying to get at. Most karts and mini choppers just have a straight pipe. In this case for joining pipes, a spot welder is not a good choice, it wont weld around the perimeter of a joint for pipes.

That welder might do, if you have 240v to plug into. Most likely a dryer or stove appliance. It looks like from the description you could hook up gas to the machine, but you will need a few more bits to do so.

 

[builder bob]

this is what i ment, using the spot welder for connecting the red parts. what's the normal exhaust temp for small engines?