Yamaha RD350 No. 9: Shocks, It Was Nothing

The RD350’s rear suspension seemed kind of springy to me, like there was no damping or the shock oil had leaked out. In corners the bike would hit a bump and bounce. Nothing frightening or dangerous but in combination with the front forks needing a rebuild anything less than smooth pavement was a ragged, unsophisticated ride. The RD still wore its original shock absorbers from 1974 so I figured it was time for a replacement set.

I found many options online, prices ranged from $500 to $50. I think we all know what option I took. Look, it’s not that I don’t want a really nice set of shocks it’s just that I’ve had some bad luck with expensive shock absorbers. In a nutshell they didn’t last very long. I mean it’s not like a dirt bike where you need good suspension. I’m using the RD350 on the street, an environment where you hardly need rear suspension at all. I found a set of shocks on ebay that looked similar to the original Yamaha shocks. For $47 shipping included I was willing to take a chance. The shocks arrived in about 3 days.

Out of the box the eBay shocks looked really well made. The chrome was beautiful, the top-mounting boss was cast aluminum and the things even have a plastic sleeve between the shock body and the spring to eliminate squeaking. The original shocks did not have this feature and squeaked a lot. They sounded like an old, rusty gate swinging in the wind when you hit a bump.

Fitment was straightforward except that the original Yamaha shocks had no bushings: the rubber inside the mounts fit directly over the shock studs. I had to press out the steel bushings on the new shock, which was fairly easy using a bench vice and a couple appropriately sized sockets. Instead of black rubber like the originals the new shocks used a material that resembled urethane and may in fact be urethane. It is translucent yellow and looks cool.

With the bushing removed the new shocks fit a bit loose on the mounting studs but not loose enough to fit a bushing. I thought about cutting a strip from an aluminum beer can and wrapping it around the stud to take up the slack but instead decided to hope that the now-bushingless urethane would relax a bit over time and swell to suit its environs. I often hope for mechanical things to fix themselves and frequently they do. The washers on either side of the stud sandwich the urethane a bit when the shock bolts are tightened so maybe they will smoosch the fit tighter.

After fitting the shocks I found the first spring preload position was too soft so I stuck a pin punch inside the nifty preload adjuster hole and cranked it up to the second position. That seemed about right. I wheeled the Yamaha out into the daylight and fired up the sweet-running two-stroke twin. It’s a sound that never gets old.

The first thing I noticed while riding was no squeaking, the eBay shocks were quiet. The roads around my place are sort of rough and there was a noticeable improvement in the bounciness department. It seemed like with the rear shocks working better the blown out front forks felt worse or maybe I just paid more attention. Corners were steadier and the rear tire rubbed the fender less than it did before. Still, it wasn’t the dramatic improvement I was shooting for. That might be down to the $47 price point.

Curious about the original shocks I compressed the spring with a long bar clamp and removed the spring collar along with the spring. Now I could test the shocks for damping action. Surprisingly both shocks still had oil in them and offered firm resistance to rebound. The compression action was much less as you would expect. It’s really hard to tell but I think the two Yamaha shocks offer slightly different hydraulic action. Certainly nothing I could feel on the road. I’ll go out on a limb here and say that there was probably nothing wrong with the original shocks. They work like they work I guess.

I’ll clean up the Yamaha shocks and pack them away to rot. In the meantime I’ll be running the eBay shocks to see if they hold up for 47 years like the originals. The new rear suspension has moved fixing the forks to the front burner. The RD350 handles well with clapped out suspension, I can’t wait to get both ends sorted and sample some of that legendary road-racer for the street performance RDs are known for.

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