New guy here. On a whim a couple weeks ago, I bought a nice running '72 T120V, as I've always wanted to build a desert sled type bike. Now that I've been reading more about these early OIF frames, I'm wondering if I should just sell it and pick up an early model. I've read several post about bracing and gusseting the frame to prevent cracking, which I'm not opposed to doing. Im just not sure doing so will help, as most of the posts I've seen talking about gussets are for road bikes, not a bike that will see frequent dirt use. I actually really like the asthetics of the OIF frame, just not sure it will stand up to use. Anyone using gusseted OIF frames offroad?
A few of us built up desert sleds for the 2019 LAB to V event. We had a Trackmaster BSA, a dry frame triumph with a 750 motor, a 76 750 and I put together a 71 650 5 speed. I had a later low frame but chose the 71 because it didn't have the vulnerable sump plate / oil feed hose arrangement. I didn't finish the run across the desert, not because of the bike but because I was getting progressively more injured from near constant dumps in the axle deep mud that year. Anyway, the bike- Betor front end from a Can Am, Aermacchi front brake, C model pipes with big heat shields, Vape ignition, 14" NJB shocks, folding pegs, tall bars, Kehin style carb. It is as near my go to as anything in my barn. Gets used on the local dirt roads and fire roads and even some single track occasionally. It can be a real handful at times but within limits, it's an absolute hoot with that big motor. I have not reinforced the frame and it has been fine even thrashed through some long rocky uphill sections. The bike has been well used and it looks the part. My email should still be in my profile If you would like pictures
Hi , My observation is every cracked back bone that I could verify with owner had binding or frozen pivots. Or… not torqued to spec. Swing arm pivot.
Actually the factory added a “gusset” on the pivot tube to back bone. Look at your lower rear fender mount ears welded to top of pivot tube. Compare this to the later frame starting in 77 or 78.
Instead of an ear sticking up it’s a rectangular piece 3/16 metal. Welded to pivot tube & extending forward to sides of back bone. It’s welded to side of back bone & prevents twisting of pivot tube. One verified case the swing arm not greased. It tore the end bushings loose on pivot tube, but back bone did not crack. I’ve never heard of a single case of the late frame cracking.
The pivot bolt locks the back bone tight to the side frame rail brackets. As I recall torque is 80#. It is listed in the ‘82&83 shop manual. I’m away from PC until Thursday where I have verify that.
The ‘71 fork was designed for the the off road BSA factory race bikes. With leak proof brand seals, phenolic damper rings & rubber boots it can work very well. Fork brace is good plan.
Proper set up & adjusted the front brake can work decently. Later longer or aftermarket longer arms gives more power. Way more.
I’ve ridden’70 TR6C many miles off road. Tons of fun & good power. Kind of heavy picking bile up after a spill. But with practice not too bad. Use heat shield over exhaust!! Just stupid not to. Hot pipe will burn you through even thick leathers. I’ve gotten pinched under bike a few times. I ran reinforced version of factory heat shield. Depends on your exhaust of course.
I’d build a desert sled out of ‘71 without a worry.
I welded reinforced gusset on my frame so it now replicates the later frame. No cracks. Did it just in case….
You keep the swing arm bushings well greased you’ll not have problems.
PM me your email & I’ll send detailed photos of my frame welding. Will send late in this week.
The photos on web of the angle iron brackets welded to all the way to cross member might be overkill. I don’t know.
I know this riding big twins off road is super fun. Don
My addition to reinforcement was to brace the swingarm. I had no cracks around the downtube-'73 frame. The motor is currently being rebuilt with Hillbilly's help and will be going into a Wasp RT3 frame. I also installed Betor 35mm forks with cartridge emulators, custom built seat, and Hillbilly and I built the high pipes. Cone Engineering silencers, Wassell carburetors, Works performance Street Tracker shocks.
Welcome to the board! Here’s a desert sled style ‘71 that a friend of mine rides through the city and out in the country a bit. He changed the side covers to match a 60s model, added Edkins style high pipes and a flat aluminum front fender. I think the OIF engines are fantastic and generally get a bad rap for not having the classic styling of the 60’s models. I can’t speak to off-road capabilities but I really like the duplex frame handling and the functionality of the conical brakes.
