After sorting out some details regarding engine mounts, I ordered a few bits of hardware (metric flathead allen bolts and 90° countersink end mills) needed to make it happen. While waiting for those to arrive, I spent nearly a week obsessing slightly over the rear suspension, which is frankly a relatively minor task on the to-do list, but one that was bugging me. At first, I really wanted to keep the monoshock arrangement. After all, that YZ swingarm was one of the concepts at the genesis for this project (I bought it years before I even got the frame), and I have already put a lot of effort into it.
But after poring over every catalog and web vendor I could find, measuring the frame and two swingarms over and over, plugging a zillion scenarios into Excel, there just wasn’t a do-able alternative I was satisfied with, including cutting and welding the YZ swingarm any of several different ways. The DT175 swingarm will need some minor tweaking to fit, and since it isn’t anything special, rigidity-wise, I thought perhaps I should brace it some. That led back to the YZ swingarm, this time with the idea of welding twin lower shock mounts onto it, to utilize the more rigid structure (with the added benefit that all the “minor tweaking” has already been done on this one). That led to another long Excel session, trying to figure out optimal wheel travel and suspension rate figures…
…and — wattayaknow — the best choice works out to 380mm, the same length I would need to use for the DT175 swingarm. I’m not going to hit my target of having 4 inches of rear wheel travel; it’s going to end up between 3.25″–3.50″. It’s not ideal, but it’s no worse than many cruisers, and it’s a whole lot better than the 1.6″ I had with the lousy monoshock arrangement. Just for reference, some data I collected while I was wading through this…
After a very, very, long online shopping session, considering everything from cheap RFYs, to even cheaper no-name knockoffs, to snowmobile shocks, to YSS, Betor, and even a well-worn pair of used Marzocchis, I finally just pulled the trigger on a pair of black RFYs. Yes, they have their problems, but for $100 they are a better solution than what I had, and should I ever find this thing to be actually rideable, I can always send them off and have them rebuilt properly for another bill.
I haven’t quite worked out whether to switch to the DT swingarm outright, or create a braced twin-shock swingarm out of the YZ. But I have made decided to abandon the monoshock arrangement once and for all, and I have suitable dampers on the way.
