Off-road Rupp Enduro Build

#1
Well here goes another off-road build. As some of you may know my last build was a full suspension bonanza that I initially built for the Gambler 500 mini bike enduro. I got 2nd my first year and the second year I had made some major improvements to the bike but the race was canceled due to Covid. Well now the race is back as everything starts getting back to normal. I was planning on finishing my bonanza but I got burnt out on that project and there’s a few issues with suspension geometry and some other things that is making me want to take a break from that project. So this year I’m starting fresh with a 1970 Rupp Enduro. I’ve always liked the Rupps and I think they are built very well and have great suspension geometry and is an overall good platform for a new build. For those of you that don’t know, the gambler 500 mini bike enduro is a 100 mile endurance race held every year in central Oregon. I also have plans to attend other events throughout the country as this style of racing and mini bikes are becoming more and more popular. I have been collecting parts for the last few months and now can start mocking things up and start building. This is what I started with.
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Pretty complete but had a hs50 that wasn’t original and overall was a little rough around the edges so I didn’t feel bad hacking it up to start this project. The plan is extended swing arm, custom triple trees and fork tubes, built predator 224 engine, bigger wheels and tires. I decided to go with these aluminum 10” wheels that are marketed as Honda Z50 wheels. They came straight from china. The quality is impressive for the price got the pair for less than $100
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Now for tires I got these Duro tires. They are much bigger than stock as you can
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Pictured next to stock 1970 Rupp tires and wheels

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These wheels use Z50 hubs and I was able to order and use these wheel hubs and brake discs. Super impressed with the quality of these parts. High quality bearings with crush sleeves and they run very true. 236FC546-F95B-4403-A1A3-4241F7080B25.jpeg
Here is the frame. There are some repairs I need to make. The main tube coming from the engine plate to the steering neck was welded crooked from the factory and is damaged at the steering neck. I’m going to cut it off and make the required repairs
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That’s all for now. Stay tuned for updates I have more parts on the way and am super motivated to get this project going. This should be a good build and I’m hoping this is one of the baddest rupps out there.
 
#3
Small update I dove into the neck as I knew there was something broken there. Sure enough it was cracked all the way through and had been repaired before poorly. So I cut off the bad portion of tube and spliced on a new piece re notched the tube and welded it all back together including a new gusset with some “speed holes” Still waiting on some parts to make this a roller fork tubes, axle bolts, and some other misc parts are on the way 89C4E66D-5E87-4716-AA0C-D8FBBD27AAD1.jpeg 1F155C66-8DF7-4C83-8801-AA2623EE8966.jpeg
 

Triley41395

Well-Known Member
#4
I'd like to build something similar one day. I can wait to see more. Are you a fabricator by trade or is welding just a skill that you picked up?
 
#5
I'd like to build something similar one day. I can wait to see more. Are you a fabricator by trade or is welding just a skill that you picked up?
I’ve always welded since I was a kid. I worked in a fab shop for 3 years right after high school but since have changed trades and I’m a commercial carpenter now
 

ELT

Active Member
#6
Small update I dove into the neck as I knew there was something broken there. Sure enough it was cracked all the way through and had been repaired before poorly. So I cut off the bad portion of tube and spliced on a new piece re notched the tube and welded it all back together including a new gusset with some “speed holes” Still waiting on some parts to make this a roller fork tubes, axle bolts, and some other misc parts are on the way View attachment 288866 View attachment 288867
Nice repair, most of the early 70 Rupp frames with a factory gusset seem to break right there.
 
#8
In my past experience stock engine plates haven’t held up to a built motor so I beefed up the stock plate by welding an 1/8 motor mount plate on top of the original. Plug welded and fully welded the perimeter. It is now around 1/4 thick and will hold up to a built engine. I also painted both the old and new engine plate with weld through primer so it will never rust between the 2 plates. A side note for anyone wondering I moved down to .025 wire to weld this thinner plate I usually use .035 but it’s too big of wire to make these smaller welds. Pics…….
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