Scoop on fitting and fettling these handy upgrades.

Scoop sorts out his RD350’S rear-end which creates another problem! Best he sort out some fork emulators!

If you own an older modern classic chances are its suspension is adequate at best and dire at worst but don’t be too disheartened, this was how they were built! It wasn’t until the mid to late 1980s that the Japanese manufacturers really got to grips with half-way decent suspension. Until that point any significant upgrades to a motorcycle’s springing and control thereof had been relatively simplistic and often haphazard. And the reasons for this were as elementary as they were obvious – most of the R&D budget had initially gone into making bikes reliable and then making them faster. Simply put there wasn’t enough dosh on hand to sort everything out at once.

Once the factories had their engines sussed they finally turned their attention to frames, brakes and (thank the gods) suspension. From there on in us lucky lot got air forks and shocks, pre-load control, compression and rebound damping adjusters etc. better described as cartridge forks. Some might argue that just a basic strong frame, decent diameter fork legs and controlled damping might have been enough for most mere mortals but no. Everything that could be made adjustable was, which allowed far too many riders access to controls about which they had no idea. That said, a properly set up suspension system is a thing of joy and can tame pretty much any aberrant behaviour this side of a fundamentally well designed bike. None of this is of any comfort to us dinosaurs that run older Japanese iron. Short of grafting new front and tail ends on there’s a limit to what can be done to improve an old bike’s handling. Take Project RD350 which has had its rear shocks upgraded – this improved the bike’s road manners to a degree but also flagged up just how inadequate the front end was. Not wanting to lamp on some upside-down forks the only option open to me was, apparently, some magic device known as an ‘emulator’. These clever gizmos control the way fork oil aka hydraulic fluid moves under compression and reacts to rebound. Following advice from my good mates at SPA Motorcycles of Cheltenham the RD350 was booked in to have some Race Tech emulators fitted; here’s how it’s done.

Job done it’s time to take it for a test ride and the transformation is amazing! Initially the most obvious difference is that the bike doesn’t sag immediately when it’s sat on; the new springs and the preload have sorted that out. At lower speeds the forks are noticeably firmer and, arguably, perhaps not as ‘comfortable’ as they were originally. Some road imperfections are possibly a little more obvious but once above 30mph the ride is totally and utterly transformed. The front-end feels extremely planted and taut; even though I wasn’t previously aware of any overt front-end vagueness it’s now obvious the RD is just so much better. Speeds, and confidence around bends have increased dramatically. Equally important the forks are much less prone to dipping at the merest sign of braking. It would take someone much better skilled to fully analyse and relay back exactly what the differences are so I’ll just finish with this. On one of my favourite test routes there’s an undulating straight with some fast winding bends at either end. Throwing the 350 into the first series of twisties the chassis finally feels like it has the racing heritage it’s said to possess and now tracks so predictably. Down the normally bouncy straight there’s now nothing but poise and precision and then we hit the second series of bends! The bike, its revised suspension and the Metzler rubber all work well together yet there’s an issue – the new confidence I’ve acquired thanks to the emulators means I’m hitting the turns 10-15 mph faster than normal and this in turn shows up the front brake’s limitations. Yes the emulators are that damn good! By addressing one profound deficiency I’ve inadvertently uncovered another which says one hell of a lot about the Race Tech kit; therefore I have no reservation in recommending their fitment, you’ll wonder how you ever got by without them. Me? Oh I’m off to the workshop and on the computer to investigate how I can sympathetically improve the RD’S front brake.

Thanks:

SPA Motorcycles of Cheltenham for advice and workshop time.

1 With the legs out of the bike the first job is to drain out the old fork oil. As the legs are coming totally apart now would be good time to clean out old oil and sludge.

7 The OEM damper rod runs two sets of cross drillings that only controlled fluid movement to a very limited degree. More holes are required.

10 Next to be loaded into the stanchions is the piston ring that Yamaha never bothered fitting to the early RDS. This part alone will vastly improve the front end’s feel but….

3 And this is the part that we need to work on – the damper rod assembly. Our example here is early 1973 and doesn’t even have a piston ring on it to control damping!

4 Inside the top of the rod is a roll pin which has to be selectively removed. We need the centre piece out but the side portions in place so as to retain the aluminium body. It’s Dremel time!

2 The hex bolt at the bottom of the leg needs to be undone. An air wrench and/or internal damper rod holder may be necessary here but whatever you use don’t bodge it!

5 The Race Tech kit comes with four different springs, each one with a specific load capacity. Here we’re using blue springs which equate to ‘pie eater’ grade!

11 …now we’re loading the emulator itself which has been set up for both the bike and myself as per the Race Tech instructions.

8 The instructions with the kit offer comprehensive instructions detailing where to drill and at what diameter. To do otherwise would be foolish and potentially dangerous.

9 With all the swarf removed and everything clean the damper rod is washed out with brake cleaner just be sure and reassembly begins. The rod is dropped into and through the bottom of the stanchions and the bottoming-out cones fitted.

6 Looking underneath the emulator body we can see the fine drillings and the base of one of the internal valves that will control the fluid’s movement.

14 Last job is to install the correct amount of oil. Then we check the forks are moving up and down without any undue sounds or impediments before fitting them back in the bike.

12 Along with the emulator we also fit the appropriate weight springs along with two lengths of hard nylon tubing which act as part of the preload.

13 Rather than have the nylon tube sliced off at a jaunty angle just using a random saw the plastic is marked using a pipe cutter then finished off to the line with fine bladed hacksaw.