It took a bit of getting used to after the CM250, but it was probably worth the effort. It being a 1979 RD400F, the last and possibly the best of the air cooled series of two stroke twins that Yamaha has inflicted on the world since the late sixties. I bought the bike two years ago, the chassis was basically stock but the engine had been reworked. Fitted with expansion chambers it seemed tuned for track use.
Initially, I kept stalling on take offs. There was no power below 6000rpm, unless you rolled on the throttle the engine sulked, spluttered and stalled. With a six speed gearbox to play with, this caused many a moment of despair as rather than screaming off up the road the engine fell into its dead zone.
On the other hand, if I hit the power hard it would rear up on the back wheel, leaving me startled, fighting the waggling front end and screaming abuse at the machine It was very trying until I got the hang of the machine. Friends who had a go came back trembling, shaking their heads in wonder and telling me it was a bloody death trap.
I eventually decided it was a wonderful street sleeper. You could pull up next to some GTi jerk who would scoff at the ancient appearance of the Yam, or at least what he could see of it through the blue smog, then drop the clutch with seven grand on the clock, bunging all my weight over the front wheel as the Yam screamed off up the road at the speed of light.
There is something about the raw way a stroker delivers its power that a four stroke can't match. The crackle of those expansion chambers, reverberating off the cringing cagers’ autos and the sheer exultation of an RD in full flight are bloody wonderful, mate.
I've done 17000 miles in two years of abuse and the motor has given no real trouble, which is pretty amazing for a bike that's spent a few years on the track and been outrageously tuned. Spark plugs only last for about 2000 miles, exhaust gaskets not much longer and I've had the downpipes crack up twice. The engine needs a decoke every 5000 miles but, unlike earlier models, the electronic ignition means the timing doesn’t need frequent attention.
The engine is rubber mounted in the frame, which was probably fine when new but the rubber had gone hard by the time I acquired the RD, so vibes came through the frame and cycle parts with quite remarkable ferocity at most revs... it took three months for the local Yamaha dealer to order some new rubber mounts, but it was well worth the wait as they made the engine appear ultra smooth.
It’s hard to say how many miles the engine has actually done but judging by the action of the gearbox one hell of a lot. As the motor has to be screamed through the box to get anywhere fast, the way it jumps out of gear in third and fourth did not exactly endear it to me. Neutral could not be engaged from a standstill and getting down through the box often needed a hefty stamp from a proper motorcycle boot. However, time and effort obviously pays off as, these days, I’m well used to the gearbox, so no great problem.
The cycle parts were more of a problem. The forks were pitted, felt loose and clanged heavily over bumps. It didn't so much as track a line through bends as leap from one horrible graunching movement to the next. The rear shocks were Konis but far from new, the springs sagged and most of their movement was taken up with a rider aboard. The swinging arm bearings allowed a small amount of lateral movement.
That the bike was rideable at all says a lot for the strength of the tubular frame. The weaving and wallowing were not so bad as to discourage me from speeding everywhere and even in that state I was able to do 120mph without frightening myself silly. Of course, it wouldn't go anywhere as fast around corners, the various worn components made it run wide in a series of lurching movements; whacking on either the front or rear single disc made the RD sit up and veer off from the required course.
I had so much trouble staying with a de-restricted TZR125 that I had to do something about the chassis. It was too embarrassing to leave it as it was. As the front brake didn’t work in the wet, the wheel was a mass of corrosion and the forks needed serious engineering work, I bought a Kawa Z650 twin disc front end from a breaker. I had to replace the steering head bearings to get this to fit and make up some spacers but it went together with surprising ease.
New swinging arm bearings were not easy to fit but a bit of work with a lump hammer and a few bruised fingers soon sorted that. Whilst the swinging arm was out I took the opportunity to paint the arm which was more rust than paint. A set of new Konis replaced the ancient ones and the rear wheel bearings were replaced as I could see rust rather than grease when I took a peek. The bike still weaved and wallowed if you went above the ton, but cornering was vastly improved, although the Yam still twitched nastily if you braked then banked over. I was now able to keep up with the TZR and burn it off on the straights.
It may have been that the frame was slightly bent, but I could not detect any misalignment in the wheels but the difference in section in tyres made it very difficult to check. I did suspect that the combination of front Dunlop and rear Cheng Shin tyre may not have helped but when I put on a matched, newish set of Dunlops there was no improvement.
The riding position was horrible, the high, wide bars and footrests mounted far too far forward. I always felt I was sat above the machine rather than on it. The original, much patched seat was comfortable for about 120 miles then turned into a plank. Unfortunately, it soaked up water and you always had a wet bum even on sunny days. My mates reckoned I kept pissing myself because of the handling of the bike!
A whole horde of us went touring on a miscellany of machines. Mine was the oldest and slowest. l was supposed to keep up with things like RG250s and CBR600s. Fortunately, on our route up to Scotland from London we stayed well clear of the motorways, but that didn't seem to limit some people who shot off into the distance on the fast straights, even when l was in the red with 120mph on the clock. It was so crazy that I was going on to reserve every 80 miles (about 30mpg!).
In the end I was left in the company of a GPz500 and TZR250, we moderated our speed to under the ton and eventually caught up with our mates who reckoned they had been at the campsite for over two hours! The RD came into its own down the Scottish back lanes where I could rev the balls off it for 50 miles at a time.
Scottish sheep are incredibly stupid, they stand in the road looking you in the eye as you boil brake fluid and burn off a month's worth of rubber trying to pull up in time. The first time it happened I got off the bike and booted the animal in the head a few times. An irate shepherd poked his head over the stone wall and cursed me. By the time he had got over the wall I was on my way again; just as well as he was swinging a big stick in the air. After that, I tended to give any sheep a slow speed nudge with the front wheel. Bloody things, they just look at you balefully and make you feel guilty.
The ride home was even crazier because it was one of the wettest days in memory. High speed in the wet on the Yamaha are a waste of time unless you actually like skidding along the tarmac. The Z650 front end was massively overbraked for the 380lbs of RD and it was very sensitive to wet weather conditions, tending to lock up the wheel, the tyre sliding away from under you. I thought I was going to die several times and my speed was so slow, 50 to 70mph, that I did not see my mates for the rest of the day.
We started out early and it was near midnight when I arrived home. The front headlamp was a horror story, although the main beam was useless it still drained off the battery power so I had to stick with dip with the occasional, hopeful flash of main beam when things became really desperate. I was totally brain dead by the time I got home.
To be fair to the bike, despite all the thrashing it never faltered once. The RG owner had to have a major engine rebuild at 24500 miles and even the GPz owner was having trouble with his camchain after a few years, so my 13 year old bike was doing very well.
Terry Holmes