Has anyone gone through the exersize of trying to modernize the suspension on one of these old guys? Know it will never be a 2012 xr-r or even a 92' but I am interested in trying to get a little more out of it.

In the short rides I have taken, pulling a little trail out of it couldn't hurt. Just from looking at it a bit more travel couldn't hurt. I'm a capable fabricator and I'm sure some bracing wouldn't hurt. With me riding it, and my kids riding it a little allocation for adjustment can't hurt.

Does anyone have a proven path in this direction? I hate to brave a new trail that runs next to a well travled road.

Are there reasonably priced adjustable length shocks out there that actually are adjustable in length not by cranking in pre-load? A disk brake front end that doesn't require a spring/cartage swap and may be a bit thicker?

What do you guys see as far as the frame and swinger holding up? Should I build a swingarm brace and brace and reinforce the frame?

I know the easier path should be to just buy a bike that has what I want, but this could be done bit by bit and be a fun project to introduce my boys to bike building. Plus, it would just be plain cool.

Back in the day We would relocate the snap ring on the front forks for more travel (need a lathe or machine shop) & then put a 1-2" spacer at the top of the fork tubes for more length. The swing arm would get about 1 1/2" in length & then longer shocks. It made the old bikes much more rideable (back then more racey). I am quite sure a later front end would work better and cheaper but you still may want to extend the swingarm. There may be a swingarm that works from another bike but unless someone has done it before it would be a trip to a salvage yard to measure up. Good luck, I think it's worth the effort!

Well, it's not a Yamaha but the 1972 Suzuki TS185 has very similar geometry with the rear shocks near vertical. I picked this up as a parts bike, and the PO had done some extensive work with new mounting points which let them put a 2" longer shock onto it. Have not yet ridden it (parts bike frame and all) but I'd assume it's an improvement as that's the direction shocks moved into the late 70s.

Original shock mounts circled in green.

My brother forward mounted the shocks for a friend back in the day who had an AT3 set up for motocross/flat track. Took shock mounts from a donor bike and reinforced them with a piece of frame tubing connecting the shock mounts to top of the backbone. The friend was happy with the rear suspension performance, and his new shocks. I think he ended up with 2 more inches of travel.

Then what to do about the front end!

I used a set of front snowmobile shocks from a mid 90s Polaris. They were nice fox mono tubes. Had to revalve them and use the stock spring but they work nice now. I don’t understand laying down the rear shock. If using the same shock it just changed the motion ratio making it softer (more leverage and travel on the spring and damper) If it is a twin tube shock it is likely getting air bubbles in the oil making the damping little to none.

2007 KTM suspension on 1974 DT360A

super plush

A good set of rear shocks would be a good start, best to just go an inch or so taller at the most, some good quality fork springs will make a difference up front, I've tried long travel mods but it handled goofy

Rob is that one of your bikes?

Yes Mark I did that a few years ago. Like LongStide said it handled goofy. I changed it to a more standard modified set up= 77 forks (adds 2 inch travel and length) with 13.5 works shocks

Did the setup work well?