The Yamaha RD350 is my fun machine. I have a little commuter for riding to work and a big four for touring chores. The stroker twin is used for evening scratching and weekend runs. It's a well loved machine but one that is still used very hard on the road. Built in 1974 it has done about 45000 miles and most of the engine is still original.
Chassis mods include a pair of Girling shocks, flatter bars and a set of modern Avon tyres. With new swinging arm bearings (never a long lasting item) and taper rollers in the steering head, the RD becomes quite a sharp handler. Stock, it wallows and weaves a bit but modified thus it can be heeled right over and holds a rigid line. At a mere 350lbs not much effort is needed to hurl it through the twisties.
In this vein it's a bit of a giant killer, with a slightly modified motor good for 110mph and blistering acceleration able to make middleweight four owners curse their girth and shake their fists as they become engulfed in the stroker's exhaust and wail.
The excellent braking helps with this kind of riding, the single front disc so powerful it'll have the back wheel off the ground and shake the forks down on their stops. The rear drum is unobtrusive, given the way the front disc tried to throw the RD into cartwheel mode isn't used very often. The front brake's a bit uncertain in the wet as there's some lag but despite its power also has a useful amount of feedback. The caliper doesn't like winters, though, needing a rebuild every couple of thousand miles.
Several times the RD has been thrust into winter commuting when my other bikes have been off the road. The main problem with town riding is that the plugs can foul. I usually fit a hard grade to suit the fantastical acceleration inherent in fun riding, but for town work a softer grade is necessary. Modern oils have removed the worst of the clouds of pollutants but sustained low rev work makes the engine sullen, coughing and spurting out oil until it clears under a bit of acceleration.
Spark plugs last anywhere between 500 and 3000 miles, depending on grade and use. As the engine's on its second oil pump there's no point blaming that particular component. Engine mods are mostly down to increased ports and a bit shaved off the cylinder head. As the baffles kept falling out, the airfilter was junked and the carbs rejetted to suit the modified motor and freer flowing induction and exhaust.
These mods worked well, although the head gaskets would blow after about 5000 miles of abuse and the engine needed a decoke every 1500 miles. The major maintenance chore was setting up the points every 500 miles. Ignition timing could go way out if that was neglected as I found out to my cost after I'd bought the bike. I was riding the Yam hard through the gears when there was a sudden loss of power and huge clouds of smoke. One of the pistons had holed. I staggered home on a 175cc single.
The gearbox was precise when I'd bought the bike but is a bit vague, these days, in the lower gears. I've heard varying stories about being able to turn it into a six speeder by removing a plate on the selectors but I also know one guy who did the trick, ended up changing up to sixth only to have the box lock up solid. I left mine as it was, even with the modified engine tune there is enough of a spread of power to make no more than five gears sufficient.
The engine isn’t entirely happy at constant revs, with a bit of surging and an odd echo in the exhaust rather than the hard edged wail under acceleration. Acceleration above 3000 revs is tolerable, between 6000 and 9000rpm brilliant. It'll cross the redline at 9500rpm in fifth down a hill, head crouched down but under that kind of abuse the vibes attack the chassis. It's not really worth the effort, given that you want the engine to last for a long time.
I had a series of electrical failures that made me question the RD's chances of surviving the year. Bulbs and fuses blowing, the battery boiling over and the engine becoming a reluctant starter had me tearing out wires and my hair in frustration. A word with some RD enthusiasts revealed that the rectifier didn't last very long. I put a new one in, which provided a solution but one that needs repeating every 8-10,000 miles. I've got a spare one already bolted in so if it fails miles from nowhere it's a lead swap rather than major disaster.
Another bit of potential horror occurred when the chrome front guard rusted through at the central bracket. Each half of the guard was sent spinning off but held to the bike by their remaining stays. The first I knew of this was the front end going berserk. I thought the wheel was breaking up. The crushed bit of chrome bore no resemblance to a mudguard. I'd noticed a bit of rust but nothing, I thought, to worry about. The rear tried to do a similar trick but I replaced it before it had a chance. At the time, new guards were being sold off cheap by one of the Yamaha dealers. I bought a new pair of wheels, as well, the old ones pitted with rust.
The only other major chassis problem was the front forks rusting and the seals blowing. I had them hard-chromed, added new seals and a set of gaiters, never had any problems from them since. The front end goes a bit vague when the tyre's down to 2mm but I get over 12000 miles out of a set so it's not that expensive to keep them in a good state.
I only ever put on the cheapest grade of chain I can get hold of, so should not complain about frequent adjustments and less than 5000 miles of life. I played around with the sprocket sizes a couple of times but ended up back with the stock ratios, taller gearing affected the acceleration quite badly (although it was very relaxed) whilst higher gearing had me trying to change up from fifth all the time and the ease with which it would go into red was a bit alarming to this long term owner.
As it was my fun machine the lack of frugality, at around 35mpg, didn't really worry me. In stock form and ridden mildly it'll do 45mpg, maybe even 50mpg on a good day. Given the choice, I'd prefer the searing acceleration and wild riding to better economy. Economy can go way off if the carbs aren't balanced every 500 miles. Something that can be done by ear unlike the ignition timing which demands gauges and strobes if holed pistons are to be avoided. The exhausts are still original if a bit blitzed by rust, helped by their inner coating of oil.
The rest of the chassis received a respray about five years ago, mostly black on black with the odd dash of bright yellow for contrast and has shown no signs of giving into rust since then. Before that respray rust was breaking out on the frame welds and swinging arm; cycle parts were faded rather than rusted, especially around the fuel tank filler, the cap always leaking a little with a full tank of petrol.
The engine's still on the original crankshaft, pistons and bores. I haven't noticed any fall off in performance, the 110mph top speed is still there as is the wheelie popping acceleration. Such abuse has probably caused the clutch rattle that started a few thousands miles ago. There's still no slip but there's some drag when starting up and after extended town work. With the vague gearbox it can require quite a bit of work to keep rolling in city traffic. Even if the engine stalls it only needs the mildest of kicks to start again, just the same as when starting from cold.
There's a lot of bias against strokers, but mine has been loads of fun, basically reliable and dead easy to work on or to upgrade to a more useful spec. There's not many 350s left on the road, but quite a few of the later RD400s. The latter are said to be better, both faster than the 350 and with a broader power band, although most of them have had their engines modified by now. Personally, I don't like their square cut looks, I think the 350 has stood the test of time much better. But then I'm very biased. Somewhere around a thousand notes will buy a very nice 350 or 400, half of that will get something that's running but is likely to need a rebuild somewhere along the line. Cheap at twice the price.
Andy