Standard or modified – suspension and compression
Other than a damn good clean and polish post fettling, the RD is pretty much there. I’d already concluded the bike wasn’t going to be restored but I’m not blind to its shortcomings. The odd rust spot, tarnished bolt or dulled chrome I can live with; after all I rather like patina. However, the Skippy the Bush Kangaroo rear suspension is something that needs looking at. So do I go for modern pattern aftermarket replicas and hope they’re okay or do I fit something more modern? If I fitted progressive fork springs and emulators in the front end no one would be any the wiser but do a pair of remote reservoir rear shocks mean The Authenticity Police will be issuing me with a summons? When does function take over from form? The bike will never be a show pony so what does it matter if I deviate away from stock a little? Expansion chambers might be an option if I didn’t have a good set of pipes but I do. And some detective work has suggested that the earlier RD350S came with some of the least restrictive, most effective, units fitted to the 1973-75 range so I’ll probably leave well alone. Perhaps my biggest current concern is the issue of compression ratios and speed of flame paths using pump petrol. My sources tell me even top grade super green is less than ideal for old strokers and the demon of detonation is still lurking ready to strike. Those that know reckon old fashioned three star would still be a better fuel for period strokers and looking at some forums I can believe this. Melted piston crowns and pockmarked combustion chambers seem to be far too prevalent for my liking. When I first worked on my 1967 Yamaha YR1 I found each head sitting on a pair of head gaskets and naively thought the previous owner was a numpty. I now recognise it was an attempt to reduce the compression ratio and give the motor an easier time when running fast burning lead free laced with ethanol. While the compression ratio was undoubtedly lowered the squish was compromised so the quick fix was less than ideal. So I’m hatching a plan to optimise squish and ease compression...