So from the beginning of building this bike I knew I wanted a bike that handled like a brand new sport bike. Rd’s wernt know for their stellar rear suspension when new and the 40 years of sitting in upstate NY made these ones good paperweights. I had looked into a few different options like Progressive and Koni and was not siked on spending the $400+ on them.
My wife had been out of town for work a few weeks and I spent lot of nights laying in bed thinking of options. What better way to get modern sport bike handling than with sport bike parts. Did a bunch of research on spring rates using the Racetech.com site and settled on a 07 Honda CBR1000rr showa unit. Its a nice unit with adjustable dampening and rebound and spring preload, plus a healthy aftermarket of parts as well. The spring rate is 11.5kg per mm and with the rd’s feather weight and my 195 lb self this puts me a bit stiffer than stock with tons of adjustments. A quick search of ebay yielded one from a low mileage bike for $25 with free shipping. I find its better to let the big bike mfg’s spend millions on R&D for their new machines and I’ll reap the benefits for my old junk.
The next problem was how to make a shock with only 1.75 inches travel work in an application that needs about 5″ total with sag and not use all the fancy linkages that honda uses on there bikes. After much thought my solution was to make second arm attached to the swingarm but shorter to reduce the radius. After a lot of math I hadn’t used in years on paper I settled on needing a 5.5 inch radius from the swingarm pivot to give the proper travel when the 15″ arm moves. I decided to draw it to scale on the welding table to check the math. It worked in practice too.
Now was the easy part of tabbing up the mounts. The rear is made out of 1.5″ square stock and the front that I forgot to take pics of is a 660 bronze bush I made on the lathe pressed into some round steel stock with a shoulder on it for the shock mount to ride on.
I also bent some round stock to act as a gusset for the rear mount and brace the swingarm. This should help with the torsional stiffness af the old arm as well.
So final verdict is that it feels like a new bike when you sit on it, It only cost $25 and the rest of the stuff I had at the shop or could be had for short money and the fab work wasn’t crazy. Ill take it. Thanks Honda