Gramps mini bike build

[wb4rt]

I'm building a mini bike from scratch plus Azusa frameless 8" kit and Predator 212 engine. I've tried to read as much as I could before and during the build. Why is it so difficult to find some basic dimensions like wheel spacing, inside frame minimums, etc.? So far I've been working on it for about a week. I go to my shop at 4:00 am for a couple of hours before going to work.

The frame is 1" square tube, which is not typical I know, but that is what I had. The only steel I've bought is a stick of 7/8" tube for the handle bars/forks and a stick of 3/16" x 1.5" cold roll for the front axle tabs. I will finish the forks in another day or 2 and then finish fabricating the motor mount/floor board.

I have cut the forks to length since this picture was taken.

Let me know your thoughts, suggestions, recommendations, or especially any CAUTIONS that I should know.

:grind::hammer:

 

[buckeye]

Welcome to OldMiniBikes.:thumbsup:

 

[TANKSAREUS]

Awesome Sir,

I have to scratch build all mine too.

I found the best thing was to get the wheels first and then go from there.

I make my own hubs and normally leave about a 1/4 between the chain and the tyre and the a 1/4 on the other side or more. Make yourself a sketch then you can add more space if needed. Then what ever the space is on the sproket side use on the other side. You can accomadate for a brake aswell in the same way. Have hordes of books with sketches and dimensions:laugh:

For a scratch builder a jackshaft is a must. The jackshaft gear can be slid left and right on the shaft so you build the rear wheel as you want it, the mount the engine center or where ever and the just adjust the sprocket for alignment easy:thumbsup:

You're looking good on the frame so far - hope the pics help

 

[wb4rt]

Hey Tank.
Great diagrams - Thanks! I may too far along now, but I'm sure I will refer back to them as I put the wheels on and adjust the spacers.

Azusa did give me basic dimensions for their frame, and so the kit would fit out of the box - Front forks 5.25" and rear 7.25". So that is exactly the width I built to. Now I have my wheels and almost ready to put them on so I can line up the engine, and finish the engine mounting plate/floor board.

I finished the front fork tabs this morning, so here is a new picture. I need to lower the handle bars 1/4" to be level with back axle. That will be easy as they are just lightly tacked to the cross bar.

Again, any comments or suggestions are greatly valued! :thumbsup:

 

[TANKSAREUS]

Very nice. You'll be riding within the week:thumbsup:

 

[incogrhino]

Foot pegs?

 

[gumpit]

Foot pegs?

isnt that what the vice grips are for?

 

[RobertC]

Hey Tank.

I finished the front fork tabs this morning, so here is a new picture.......

Again, any comments or suggestions are greatly valued! :thumbsup:

Hey WB4RT,

That frame is beautiful. The shape of the back reminds me of some of the 'trail' scooters or trail minibikes, like the Tule Trooper, or a pac-mules, etc. The forks / handle bars you created have a great shape of their own.

Looking forward to seeing the continued progress.

 

[Glenn]

Looking good :thumbsup:

 

[wb4rt]

Worked on it some more this morning, but not a lot to show. Plan to put in the engine mount plate/floorboard this week-end.

Here is a picture of the parts I made for the front tabs if anyone is interested.

 

[wb4rt]

The STICKY says to post pictures of the whole build, so I'll add these in case someone is starting a new build.

So going back to the beginning of initial material. You will see I thought I would just angle the two sides, but decided that the square tube would work and look better to be square, so I cut the frame and added in some mitre angles, 11 degrees.

 

[wb4rt]

More pictures to get caught up:

 

[Harleys Papa]

I need to lower the handle bars 1/4" to be level with back axle.

Welcome to the forum wb4rt :thumbsup: Do you really think you need to lower the bars :shrug: They look a little low to me already :shrug:

 

[wb4rt]

Thanks, Harley.

I only lowered the handle bars 1/4" to be level with back axle. I'm sure it wouldn't make any difference, just like to be as exact as I can. It's hard to tell in this picture but I think the bars are a good height. I still have to trim them once I get ready to install the grips. I hope the seat doesn't raise me too much! My wife and I are about ready to build the seat too. It's going to be a big seat so we can both ride!

This week-end I will add the wheels and align the engine plate so I can cut the slots. I have to add a pin for the brakes and a bar for the back fenders.

Anybody have an opinion on a fixed bar for the front foot rests? I have a pair of foldable rests, but wondering what is better.

 

[Harleys Papa]

Thanks, Harley.

I only lowered the handle bars 1/4" to be level with back axle.

Anybody have an opinion on a fixed bar for the front foot rests? I have a pair of foldable rests, but wondering what is better.

Ok I'm not sure what you mean by "to be level with back axel"

As far as foot pegs :shrug: I guess that's personal preference :thumbsup: I have a VT3 with forward pegs that is great for cruising but my Speedway has mid pegs and that's great for racing :thumbsup:

VT3

Speedway

 

[wb4rt]

I lowered the handle bars through the tree, so the front axle would be level with the back axle. I did not cut the handle bars down.

I think it is a good height, but will know more after I get my seat on. I started building it with my grandsons in mind and did not want it to be too big or too fast, but I may have missed that! Going to put a Predator 212 on it. Clutch is 12T and sprocket is 72T.

Think that will be ok?

 

[Glenn]

Regarding foot pegs, I would recommend folding style, and a pair up front for you, and a pair out back for her.

Here is a snapshot of my Gran Prix Mini Bike that I have heavily modified, but you can see how I did my foot rest pegs so my wife can ride with me.

I also made our seat as long as I thought would look good and had it padded really good, because I'm 57 with a bad back :crying:

 

[Glenn]

I lowered the handle bars through the tree, so the front axle would be level with the back axle. I did not cut the handle bars down.

I think it is a good height, but will know more after I get my seat on. I started building it with my grandsons in mind and did not want it to be too big or too fast, but I may have missed that! Going to put a Predator 212 on it. Clutch is 12T and sprocket is 72T.

Think that will be ok?

Regarding the chain, I broke regular #35 chain with two of us, so I switched to the High Performance "Gold" Racing Chain and have had no issues.
Here is a link to what I'm referring to: #35 RLV X-treme Performance Kart Chain "Gold on Black" 106 Links - RLV-0850

 

[Harleys Papa]

I lowered the handle bars through the tree, so the front axle would be level with the back axle. I did not cut the handle bars down.

I think it is a good height, but will know more after I get my seat on. I started building it with my grandsons in mind and did not want it to be too big or too fast, but I may have missed that! Going to put a Predator 212 on it. Clutch is 12T and sprocket is 72T.

Think that will be ok?

I think that will be fine, there are several speed calculators that will give you top speed determined by you gear ratio and tire size and max rpm's :thumbsup: There is a throttle limiting screw on that engine :thumbsup: but I found with my grandkids you need a good return spring too :thumbsup: they will either hit something or scare the crap out of them self's :scared:

 

[wb4rt]

My wife and I made a simple seat on Saturday. The recommended foam is pretty hard, and the seat is wide. We may re-think it and make another version.

The handle bars are a little low now with the seat. You were right about that Harley. I think I will either 1. cut and extend the handle bars up, 2. re-work the top of the frame and lower it 3" while making it taper instead of being so wide the whole length, or 3. do both. Those are probably future mods. I believe I will continue to finish per the original design and ride it a while before I cut into the frame. That way I will have a better idea of what is really needed.

Anyway, here is a picture as of today. Starting to look like a mini bike! Once I finish welding the other items like the brake tab, trimming the handle bars, etc. I will take everything off to make a couple of enhancements to the motor plate etc., then prime and paint. I made a simple jig for my plasma cutter to cut the engine bolt slots.

I am thinking I would like to add a short pipe to the rear oil drain so I can change the oil without spilling it all over the mounting plate. It seems to be a 10mm plug. Anybody have a suggestion on where to get a 10mm pipe and coupling? Or a better idea?