Thread: mini bike frame

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Mini bikes and hot rods go together right. I found another project for the kids and I . I found a old minibike bare frame for 25 dollars that I want to get going for the kids. I have a small problem though. The frame seems to have got some water in the tube that supports the motor. I does not look that bad to me but will pretty much be impossible to tell over the internet the integrity of the tubes. I want to make some kind of wire brush with a extension on it to send in down the tubes and clean any rust in the interior of the tubes. Then fill the tubes with some type of rust converter/primer. Tap the cracks shut and weld and finish. I guess best would be to cut some tubing in half and weld some pieces in over the cracked area. Then I want to wire brush the frame and put some naval jelly on it to take care of the surface rust and paint. Any ideas on this project are welcomed. Thanks

Nice find! I still have my dad's Sears mini bike. Still runs too, just isnt too quick with my 300+lb body on it! Haha!

Looks like those tubes that drop down below the engine are open at the back ends. I don't think I would worry about trying to get a brush inside, but if you're worried about internal rust you could maybe thin down some rust encapsulating paint a bit, pour a cup in the tube and turn it every which way to coat the inside and then dump out the extra. That would be after pounding the cracks together and welding them up. The pipes that are sealed both ends and no cracks should be fine, right?

Great find for $25, BTW!

Thanks
From what I have found out is that its a RUPP "Continental" from the late 60's. Great its older then I thought.
What would be best to refinish the paint? I was going to use some type of rust converter on the rust and sand, not taking off as much of the original paint if I dont have too. I am stuck with rattle cans though. Heres a pic of 2 bikes thats been restore. Pretty basic bike , but thats a good thing IMO.

Very cool little project. About 8 months ago I, for some reason I can't explain. got a hankering to build a mini bike. Found a frame on Craigslist for $ 50, replaced every part on it from an on line mini bike company, and bought a 6.5 hp motor from Harbor Freight. Sprayed it bright yellow, and even put a new seat on it. I took it for a quick spin and it scares me to death, so it just sits, collecting dust now. I came to the realization that at 65 it wasn't as much fun as the one I owned when I was 12.

If you need any parts, this is the place I bought mine at. Nice people and they carry most everything mini bike related.

Go Kart & Mini Bike Parts

Don

At least my Son got some use out of it.

Originally Posted by BigTruckDriver

Thanks
From what I have found out is that its a RUPP "Continental" from the late 60's. Great its older then I thought.
What would be best to refinish the paint? I was going to use some type of rust converter on the rust and sand, not taking off as much of the original paint if I dont have too. I am stuck with rattle cans though. Heres a pic of 2 bikes thats been restore. Pretty basic bike , but thats a good thing IMO.

BigTruckDriver,
When you say you want to "...not take off as much of the original paint...." do you mean you want to keep the old patina, making it look its age; or do you mean that you don't want to strip it to bare metal before painting? If you're wanting to refinish the frame like those in the pictures just sand it smooth, and get a primer and finish color from Krylon or Rustoleum. A metal etching primer would be a bonus if they have it. Rattle can paint is very thin to atomize through that small orifice, so you need to put on three or four thin coats at each step to get a good coat of finish.

Originally Posted by rspears

BigTruckDriver,
When you say you want to "...not take off as much of the original paint...." do you mean you want to keep the old patina, making it look its age; or do you mean that you don't want to strip it to bare metal before painting? If you're wanting to refinish the frame like those in the pictures just sand it smooth, and get a primer and finish color from Krylon or Rustoleum. A metal etching primer would be a bonus if they have it. Rattle can paint is very thin to atomize through that small orifice, so you need to put on three or four thin coats at each step to get a good coat of finish.

Thanks for the input guys.
Itoldyouso= your a dare devil,lol. 6.5hp, that motors HUGE. The bike looks beautiful though.
Rspears= No I dont want the original patina , I just didnt want to strip it too bare metal as you said. After taking it apart though I think stripping it would be best.

I'd go with Por 15 for inside the frame. The stuff coats and coverts rust, and a little goes a long way. It is a very thin paint that should take care of any rust issues you have, then maybe go with less of the "Tim the tool man Taylor" approach, as Don said, more power on one of those can be scary!
Had a friend put a huge marine patrol out board on a small cubby cabin fishing boat, used to be like putting your life in your hands going out in his boat, especially before he put a floor in over the exposed stringers. Lightening quick power and no stable platform equals disaster!

Originally Posted by stovens

I'd go with Por 15 for inside the frame. The stuff coats and coverts rust, and a little goes a long way. It is a very thin paint that should take care of any rust issues you have, then maybe go with less of the "Tim the tool man Taylor" approach, as Don said, more power on one of those can be scary!
Had a friend put a huge marine patrol out board on a small cubby cabin fishing boat, used to be like putting your life in your hands going out in his boat, especially before he put a floor in over the exposed stringers. Lightening quick power and no stable platform equals disaster!

POR 15 has crossed my mind,lol. I used the stuff on a rear end and applied it with a brush. It leveled out and is a thick coating that attaches to the metal real good. Have you tried to top coat POR 15 with a rattle can? I think I might sand blast the frame and use the POR to seal the frame up and then top coat. I think that would be as durable as I can do in my garage.

EDIT: looking on the web top coating POR is kinda iffy. 50% say yes no problems and 50% so no bad idea. Maybe I just do the insides of the tubes as you suggested. I will be sandblasting the frame now(change in plans) I need to go to the paint shop and get some self etching primer and paint in spray cans. What type of paint would be best , most durable, got 3 young ones that will try there best to tear it up,lol?

Don

You've got to have a picture with smoke coming off the back tire. Cmon!

i treated the floor and bed of my 63 willys jeep with POR .
then painted it with farm implement paint.
it worked just fine.
POR left expsoed to sunlight turns an odd grey color.
that stuff is tough!

Just saw this thread - great find on the old Rupp frame. Had several mini-bikes in the 60's - what a blast. I once built a mini-bike with a MAC 101 (two stroke racing cart engine) and that thing would flat out scream - but oh the front end wobble with those little tires!!

By the way, the cracks are caused by water getting inside the frame and freezing (just like a pipe in your house!). I've fixed several of them and you need to know that you can blow right through the tubing if you're not real careful. Of course, my experience was using a Lincoln arc welder and i probably had it set a wee bit to high!

a 3-5 HP Briggs is perfect for these buggers. If kids are going to be primary riders, I'd stay closer to a three horse and keep the final drive a bit higher or they'll launch like a Nike-Zeus rocket. If adults ride a five is okay with a bit more gear through the jack-shaft as we tend to have the "bulk" required to keep the front end down...

Have fun and let us see the results!
Glenn

Originally Posted by Mark in Memphis

Don

You've got to have a picture with smoke coming off the back tire. Cmon!

Haha, no smoke, but the front end gets real light when I cranked it open. Then, when I laid off of the gas I felt like I was going to do a header over the handlebars. I guess I was a little more agile 53 years ago when I had my first one.

I agree with Glenn.....3-5 hp is much more sensible. The 6.5 is physically a little bigger (less footroom) plus it is just waaaaaaaaaaaaaaaaaaaaaaaaaaaaay too much hp.

Don

Originally Posted by Itoldyouso

Haha, no smoke, but the front end gets real light when I cranked it open. Then, when I laid off of the gas I felt like I was going to do a header over the handlebars. I guess I was a little more agile 53 years ago when I had my first one.

I agree with Glenn.....3-5 hp is much more sensible. The 6.5 is physically a little bigger (less footroom) plus it is just waaaaaaaaaaaaaaaaaaaaaaaaaaaaay too much hp.

Don

Don,
Comparing the pic's of your beautiful yellow bike with the two that BTD posted I noticed that your foot pegs were a lot farther back than the others, which I think would add to the feeling of instability, especially at speed. I would think that having your feet about a foot or more shifted forward would help, but then I've not ridden a mini bike for about 40+ years

After looking at the frame pics, not so sure it wouldn't be best to just replace the cracked sections with some new tube and internal slugs to help hold things together.... Hate to see it break there, underpower with a rider on it!!!!