Being the piddler that I am and having access to some really great tools, I have wanted to build a four wheeler chassis completely from scratch using dimensions and geometry figures from either a Raptor or TRX250R frame.

I was wondering if any of you have done this. I am trying to decide if I want to use round tubing or square tubing, all in mild steel. Sure, I know it's a little heavier than aluminum, alloy or chromoly, but it's affordable, highly workable and strong. And, in the right guage not much heavier than the aforementioned metals.

If you have done this before, I am hoping you will share your experience and some pointers for me and others that may be wanting to tackle this sort of project.

Thank you for reading this. Any and all reponses appreciated.

 

Build the chassis on the 250r geometry, I think almost everyone will agree that its the best handling quad made. What kinda motor are you planning to put in there? I might be interested in purchasing one of your homemade frames if you do try it and it works out, as mine is starting to get kinda old and such, but I dont want to pay 2 grand for an aftermarket thats out there. I would suggest that you use the round tubing as it seems to be a little stronger or something I read.

 

*cough* 400EX *cough*

Round is supposeded to be stronger, and it should be lighter comparing the two in equal diameter...

Good luck.

 

Thank you for the responses.

rhino99, I probably won't ever make a frame for someone else, but thanks for asking. We live in a very letigious society nowadays and the liability would keep me awake at night. Besides, I will have a hard enough time just trying to scrounge the time to build my own.

I had planned on using an old Honda streetbike engine, but have since decided that it might not be worth the trouble. That engine would be better suited for something such as a dune buggy frame. Instead, I think I will keep my eyes open for something else. I would like a big bore motor (250 up), but I'll just wait and see what I run across.

1986SuZuKiQuAdRaCeR,400EX, huh? Hmm...may have to look into that. I didn't think there was much difference in the 400EX and 250R frames anyway. Is there?

On the subject of round tube vs. square tube for steel, I may be wrong on this but I believe square is actually stronger than round tubing of the same guage and steel. However, there are certain types of steel only available in round tubing that makes it as strong or stronger than square tubing. Round tubing is usually more lightweight and much less troublesome to bend, but as far as cutting, squaring up and welding, square tubing is easier to work with. Like I said, I may be wrong on this but....I'll do some more research.

As far as what Rhino said about the aftermarket frames costing $2k+, that just blows my little ol' mind...I can't for the life of me understand why they are so high! There's not that much to an ATV chassis! Has anyone else noticed this lately? And what about those custom A-Arms? $800 for a set? Good gracious!! For a whole set of A-Arms, they can't be using 15ft of whatever tubing they are using. There's not much material there nor is there much labor. They cut 'em, bend 'em and weld 'em. Probably takes all of 30 minutes to make a good set using the tools they use. Maybe less. Even using chromoly, T-6, or whatever, I just can't believe that. Sort of reminds me of the deerstand manufacturers....but that's a different story.

After seeing a few customs, I just have an itch to build me a quad from the ground up, mostly just to see if I can build a good one. It's a long term project. I don't even own a quad of any sort right now.

I will probably start by building my little son a mini-quad using go-kart components. That shouldn't be too hard. I have seen one on the 'net that was built using minibike parts and an 8hp Tecumseh and it would top out at 40mph. It had full suspension and looked better than many of the mini-quads I have seen from the big manufacturers.

I know, it's a nutty proposition, but I still want to do it.

 

Speaking of mini-quads, if you were to build a chassis for say a KX60 or CR80 motor or something such as that, and it worked out to be a good chassis, and you made it to work with 250r suspension, etc, there could be potentially a lot of money to be made building 90mods for national riders. Just something to think aboutif you are skilled enough. I know what you mean about the chance for lawsuits, etc, and if you were to do that you would have to have some sort of insurance against that kinda thing, but if you were a good enough welder, the potential is there to make yourself some cash.

As far as a 400ex vs 250r frame, the R's use square tubing while the 400's use round, thats the main difference in the two. The 400 also has SLIGHTLY different suspension setup in front, mainly longer front shocks that makes the R sit a little lower and handle a little better. As far as I know thats pretty well the difference between the two. You might be better served to find a decent big bore 250r, a 330 or 350 or something along those lines, ride it till you break the frame and then go to work on your own.

 

I've got a 250R motor for you to use if you go through with this project. As for the mini, as rhino said, try and build a "mini 250R". I want to get my little brother into racing but these chinese POS mini's are worthless. I have thought about attempting what you are, but don't have access to any of the tool required to do so. Let us know how it goes and post pics.

 

ltracerx,
How much would you want for that 250R motor? I might be interested.

As far as the minis go, I agree with y'all about the Chinese built minis. For the life of me I can't understand why the big companies can't build their own minis so that they are worth something.

Back years ago when quads were still a new "fad", I remember seeing various articles about mini quads built from the 80cc racing bikes, and even a KX60. Those quads were built just like their 250cc counterparts, the Quadracer 250 and the Honda TRX250R. Why that hasn't caught on over the past nearly 20 years is unforgiveable. I remember looking at pictures of CR80 and KX80 quads and just drooling with envy.

 

I don't know for sure if I want to sell it. The motor runs, but it needs the lower rod bearing replaced(if you do it yourself, couple hundred dollars). I'd like to sell the whole bike first but if I can't, I'll sell the motor alone aftfer I figure out what it's worth. PM me about it so the post doesn't get deleted by the moderators.

 

i've been looking into a similar project. i want to build a chassis with 250r suspension geometry around my rotax 400cc 2 stroke. it's got crazy torque, pulling 3rd gear wheelie's with my 300lbs on it in the atk 406. the weather and terrain in pa are more suited to quads than bikes most of the year. so i have built tubular frames for formulaSAE when i was in college. round tube is stronger than square, it resists buckling better in compression and torsion than square. if you size it the same as the stock frame, you most likely won't run into strength issues with either. the advantage of square tubing is that you can use miter's to join it. round tubing requires notching with a hole saw jig or something similar. i've been trying to get good dimensions for the suspension mounting points and all the a-arm lengths, and swingarm length. i'm trying to get in touch with a friend of a friend who has a bare frame which i may be able to borrow make some good drawings from, but things like that always take awhile to happen. definitely stick with mild steel. chromoly is a whole lot harder to cut and bend, and requires post weld heat treatment. chassis shop is a really good source for alot of the small things you need to build a chassis. they have a decent catalog for free from their website. i'd be interested in keeping in contact, let me know how you are going.

mike

 

munker,

Thanks for the response and the info about the round tubing. I stand corrected!

If time permits, I may go ahead a make a frame mockup out of some scrap EMT conduit I have access to. EMT is fun to piddle with for stuff like this.