Motorbike forks for a minibike

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bighead

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Find a bigger motorcycle rear wheel friend. I do not like that rear wheel with the large front wheel. Perhaps you can find a replacement wheel for that model. You would have a great or greater start then.

A motor cycle rer wheel will also give you brakes and a sprocket.
 

The Mechtician

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I've never seen a pair of forks seize before! You'll have to take them apart. Pop the axle caps off, there should be an allen head bolt under there holding the valve assembly into the fork tube. Spin it out with an impact wrench or a drill, something with a lot of inertia and high speed. Take the spring caps off the top of the forks, remove the fork springs (bet you $100 they'll be rusty!) and then separate the fork leg from the fork tube. Do it over a bucket in case there's any oil left in the forks, cuz that stuff stinks!!

As for the engine, I bet it would fit in your frame if you got rid of that horrible pulsa-jet carb and fuel tank. You'd have to source a different carb or make an adapter, and maybe source a different fuel tank (or make one) to mount on the bike. Overall though, it would be less work & easier to do than cutting your frame & extending it to fit the engine in. Just my 0.02, it's your bike, do what you want :D
 

bighead

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Now way. No offense Blue.

Keep it simple landuse.

I would look into tilting the engine so to make it fit. I am not an engine guy but perhaps you can tilt it that much with little to no mods. Ask around I bet you could find out if it would work. Or find a or trade for an engine that you can remote the tank easy. Does anyone know how much you can tilt a engine and run good?

I will be looking at your frame and coming up with ideas. I love that stuff and drive T-man crazy with it. Thinking how you can add a tank on it now. Can you take a pic looking down on the frame? Like when you are sitting on it.

If you cut anything I would extend the bars where the motor bolts to. And slightly change the angle of the down tube. Are you sure those forks work? Or are the fake?

Also when you mount the engine. Make sure the PTO and the swingarm pivot point are level. This way your chain is not doing crazy stuff.

 

landuse

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Bighead: Thanks for the input. I have also no idea if that engine would work at an angle. When I got the frame I was planning on just cutting the forks off it so that I wouldn't have to make any myself. Seeing that I got the whole thing, I thought I would use most of it, but then found that the engine did not fit in (which was a bummer). The frame is also %$#@ heavy. When I get home I will see if I can tilt the engine into that hole, but I have my doubts.

I then had the idea to cut the frame as shown in the pic below, and then weld up a back end with the steel I have for the bike (like Bluethunder suggested). Oh....I will take that pic you wanted when I get home from work.

As I said, I was planning on cutting the frame at the spot where the motor bolts onto, and then extending it, like you suggested. I was just not too sure what you meant by down pipe. Is it the one that I marked as such in the pic?

As for the forks, I just assume that they should be working. I am going to try and take them apart this weekend and see what is going on there. I have been doing a bit of research, and I think I should be able to do it. If I can't, I am sure some kind people here would be able to help me out. :D Do you get fake forks on bikes??

I found these numbers on the neck of the frame

LAAJCML1661034353
86900503

I know the first is the VIN, but I am not too sure what the second one is for. Can anyone maybe tell me, from looking at the VIN, what make and model bike this frame is from. I did an internet search, but pretty much came up with China as the country of make. I don't know if this is correct though.
 

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bighead

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To much cutting friend. I would cut the under where the motor wold go. cut both those bars and extend them some. Then cut the down bar and slightly change the angle.

No need to cut the main frame.
 

landuse

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Bighead - i took the pics of the top of the frame for you. This is the first pic. In the second and third pic, you will see my attempt at getting the engine into the frame. I have an idea that I might actually be able to get it in. In the third pic, you can see 2 metal tubes that protrude from the side of the frame. I am not too sure what they are for, but if i cut them off, I might be able to get the engine in.

What are these 'tubes' that are stopping the gas tank fitting? I will see if I can take them off this weekend and see if the engine will then fit.

I also took some photos of the forks to see if they were fake or not. I pulled the dust cover up on the one fork, and you can see that they are definately supposed to work. You can see the circlip etc in there that needs to be removed when dissasembled. I also took a pic of the bottom of the fork, and you can see the hex nut on the bottom that holds the damper rod that in turn holds the inner fork tube in the outer tube. These are pics 4 and 5. I am going to take them apart this weekend and see if I can get them working again. The last pic shows the bolts that hold the forks onto the frame.

Bighead - would you adapt the frame as shown in the last pic. Is that what you meant??
 

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bighead

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Yes the last pic is how I would do it. I would cut both bars under the moter. Then cut the down tube ALL MOST ALL THE WAY OFF. Stop once you cut the the 3 sides but do not cut it all the way off. Then just bend it down/out to where you want it. Then make the two bottom bars under the motor longer as needed. Then the space/gap on the down tub from bending down/out? Just weld some flate stock over that part on all 3 sides. You do not have to bend it far. Nice and clean. probably take you a few hours.

This way you never have the frame in bunch of cut parts. Will make easy mock as well for your frame is never really cut up. Just slice the down tube. Pull the down tube out. Then add the longer bars under the moter. Simple really.

Did you follow that?
 

landuse

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Thanks Bighead, yes I did follow that. Once I have cut the 3 sides of the tube I can bend it wider, pivoting on the last side which I did not cut.

Have you any idea what those round tubes are that I put red circles around? Could I get rid of them? They aren't for anything important are they?

I am probably going to have to get a shock for the back swingarm.
  • Have you any idea how I would size the shock. I can't figure out what type of bike this was, so I am not too sure what size shock is needed.
  • Also, where would the shock connect to the swingarm and the frame.
  • Do I need 2 shocks?
 

bighead

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Thanks Bighead, yes I did follow that. Once I have cut the 3 sides of the tube I can bend it wider, pivoting on the last side which I did not cut.

Have you any idea what those round tubes are that I put red circles around? Could I get rid of them? They aren't for anything important are they?

I am probably going to have to get a shock for the back swingarm.
  • Have you any idea how I would size the shock. I can't figure out what type of bike this was, so I am not too sure what size shock is needed.
  • Also, where would the shock connect to the swingarm and the frame.
  • Do I need 2 shocks?

Sorry I do not know what those are for. If it is not for the shock mount then chance are you do not need them.

I would try to ID what type of frame you have. Then find pics of the shock the bike originaly had. Then go from there. Or you can just buy a pitbike/dirtbike style shock. And then make a bracket that has like 4 holes to adjust it for perfect fit. This way if it is to short or to long just move it up or down a hole. I would try to mod a real bike mono shock back there. You would be able to mosh much harder. Maybe a 125 shock or something. Also make sure your tank it not going to hit anything when the suspension is at full travel. You said that frame is heavy? Thats a good thing if you ask me.

I would try like hell to source a original complete back wheel and axle with chain tensioners. Will save you lots of time and work. After you have the wheel you can think of ideas to make the frame look cool with some side panels or something.

Also Bluethunder might now your questions. He dinks with these things.
 

landuse

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Thanks Bighead. I tried to ID the frame, but I think it is some chinese make, and I couldn't get an ID using google and the VIN number off the frame. I posted the numbers above here somewhere.

Oh well....maybe Bluethunder will weigh in here again
 

bighead

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Now that I mention It I have a mx100 yamaha rear wheel with hub and sprocket. If it will work you can have it. Just pay the shipping what ever that would be to africa. I can measure it and take a pic if you like.

I am thinking you might be able to find a 80cc wheel there though right?
 

bighead

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Thanks Bighead, yes I did follow that. Once I have cut the 3 sides of the tube I can bend it wider, pivoting on the last side which I did not cut.

Have you any idea what those round tubes are that I put red circles around? Could I get rid of them? They aren't for anything important are they?

I am probably going to have to get a shock for the back swingarm.
  • Have you any idea how I would size the shock. I can't figure out what type of bike this was, so I am not too sure what size shock is needed.
    [*]Also, where would the shock connect to the swingarm and the frame.
    [*]Do I need 2 shocks?


There should be mounting tabs on your frame for the shock mounts. You need a single mono shock. Or you could go old school and use two shocks on each side.

A mono shock has the sinlge shock inside the frame and swingarm.

You are goig to have to spend hours on google looking at china pitbike until you id your frame. Or atleast another swingarm that has the same wheel you need. Finding a wheel is not so bad. You were going to build a whole bike remember? The wheel will have brakes sprocket as well.

Whats your plan for a rear wheel? Any ideas?
 

landuse

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Thanks for the offer of the wheel Bighead, but I think the shipping here to South Africa would probably be as much as a brand new wheel (or bike). If I really get stuck I will have a look at it though. I will probably be able to get something secondhand though.

Having a look at one of my pics, I am assuming that the shock mounts are the areas that I have circled. The top mount looks right, but the bottem one looks as if the brackets are a little too wide apart. What do you think?
 

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The Mechtician

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Mechtician - the process you gave for disassembling forks...is it the same for pretty much any forks, or for ones that look like mine?
If you've seen one you've seen 'em all, telescopic forks are relatively simple and as a result tend to be quite similar. The fork design on your bike has been in use since the 60's, so I'm quite confident that the disassembly procedure I detailed in my previous post will be 90% correct :thumbsup: I would also say that China is most likely the country of origin for your bike, most bikes of that size and shape (around these parts, anyway) are Chinese "pit bikes" sold for peanuts, ridden hard and put away wet.
 

landuse

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Well, I tookthe shocks apart yesterday and sorted them out. They now work fine. I will post some pics and tell you all what I think the problem was. My internet is a bit shaky at the moment, so I am not even going to try and post some pics now.

Bighead - you are probably going to hate me, but I think I am going to go more with Bluethunders idea. I will post all the pics tomorrow
 

landuse

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Right, so I did some work this weekend. The forks as I have mentioned were not working at all, so I decided to take them apart and see what the problem was. I took Mechticians instructions, as well as some I found on the net, and got working. I first undid the bolts on the top of the forks to see what it looked like inside. I unfortunately didn't take a photo of that, but all you could really see were the fork springs, as well as the oil. Suprisingly, there was enough oil and the springs looked like they were in good shape. No rust at all.

As I was taking the bolts off (pic 1), I could hear air escaping from the inside of the forks. I thought this a little weird, but didn't really pay much attention. I then decided to put the bolts back on and take the forks out of their frame. When I had them out, and pushed down on them, they now worked!!!!! I think the problem was that there was an air build-up inside, and the presure was too much for them to compress. So I didn't have to take them apart at all!!! Yeah. Problem 1 sorted out.

I was going to go with Bigheads idea of keeping the frame 'as is', and just cutting the down tube and bending it for more engine room. I then realised that my jackshaft would still not fit, and there would be too much frame in the way for my chain to reach the rear wheel anyway. I would also need to get a shock for the rear (which I know would be a headache trying to find cheap). I would also try have to line the PTO and swingarm up etc etc.

I therefor decided to go the route of more cutting and welding, but easier on my non existant mechanical skills and knowledge. I therefor bit the bullet and did some cutting. The third pic is where I cut the top part of the frame, and the fourth is the whole frame cut. I tried to retain as much of the original frame parts so that i could use them later (like the seat bracket and the footpegs). The swingarm is also still intact if I ever need it. When I cut through the motor mount frame, I got this foul smelling water pouring out. It must have somehow gotten in there from standing outside all this time.

The last pic sort of shows what I am going to do. I will use the square tubing I have to extend the motor mount area as well as the top of the frame. I will then fab something for the rear wheel to connect to.

As you can see, the engine now fits in there nicely.

Let me know if anyone has ideas that might help me
 

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