On a low-life tour of Europe I saw one of the first XT500s, a thinly disguised road going version of the TT enduro iron that had cleaned up the Yank circuits. To a Tiger Cub man weaned on 10hp, this monster, with that shocking great cylinder head trying to poke through the tank, was strong medicine. I wanted one.
I finally bought my XT as an unfinished project, through a pal in the trade. I had waited the best part of a year to find one, and it occurred to me at various times that they seemed a bit rare, considering how popular they had been when first introduced. I should have realised that there was probably a good reason for this, but love is blind...
The previous owner was one of those sorts who think that red paint is a substitute for money. Rather than give the motor the rebore it desperately needed, he’d painted the frame red. Rather than buy any new gaskets or oil seals, he’d painted the tank red. And added Red Hermetite to the old gaskets. Cables had been meticulously clad in lurid yellow sheathing, but not oiled, alloy parts had been polished to a mirror shine, but the points were pitted beyond salvage. You get the picture?
A few moments running after about 200 kicks revealed massive oil leaks around the head, and the red gasket oozing out all around the mating faces of head, barrel and rocker box, convinced me that it was not sane to go on. Sure enough, removing the sludge traps revealed them to be full of red gunge, and the oil filter element was an old, partially collapsed, item that a certain mental snail had deemed fit to go back into the motor.
Fortunately, there are no return oil feeds in the XT - the oil runs down the valve gear and then just pours off down the camchain tunnel. In any other motor, such use of Hermetite would have needed a complete strip to clean it all out again. Was this the beast that so fired my imagination?
The two valve, four stroke engine was of very conventional, if not outdated, design. The Japs commenced development of the XT exactly where BSA had left off with the last B44. This bike, especially in Cheney Victor form, had demonstrated the potential of the big single to deliver modern levels of performance in a compact, lightweight format with adequate concessions to road use.
The engine had become as snappy as possible using pushrods, whilst the stroke had become shorter and shorter to allow higher revs and produce freer breathing. Yamaha explored these themes further, with a short stroke (87 x 84mm), OHC engine featuring a light, short skirted piston. Though huge by Japanese standards, the flywheel still let the 9:1 compression motor spin very freely. The result was a real short-stroke Manx motor (oops, just drowned the editor’s desk in irate letters) and once laced into an oil bearing frame (suspiciously similar to some BSA items) the motor was really sweet and went well when new!
Much hassle ensued before the motor was able to perform in something approaching a normal manner. A rebore was the first priority. No trouble getting the seals, gaskets and various odd bolts, but the piston was ten weeks. I was lucky, back in 1980 a friend had to wait for 19 weeks and this was when they were still in production! The piston is a real problem with the XT because the skirt is so short that the piston tries to rotate about the gudgeon pin with every stroke. This wears everything out double quick and even new pistons clatter like mad. Strangely, the SR500 has a piston with a longer skirt and this may fit the XT.
Everything else had survived surprisingly well - cam lobes, valve stems and rockers were barely worn (the age of the bike was indeterminate as the speedo drive worm had seized at 20000 - it could have done two or three times that). Putting it back together was no problem I can recommend this as an easy motor to work on. The internals, except the piston, are pretty butch and sizeable, the clutch in particular seemed very strong. It’s a pity that Yamaha got the electrics wrong. The separate ignition generator was hardly up to raising a kitten’s fart, and if there’s one thing a big single needs it’s a fat spark.
Combined with the poor carb it all but managed to wreck the usability of the big single. The problem with the XT was that the head became very hot (partly due to the restricted oil cooling from a very thin supply pipe to the head), whilst the carb also had to feed a cold motor without flooding. It didn’t work all that well. Unless all the adjustments are spot on, a huge power gap occurs during take off instead of the usual slight hiccup.
The SR had an accelerator pump fitted and the final XT motor combined a flat slide carb and CV carb in a twin choke setup. The carb on the 500 also featured twin cables operated by a bellcrank, that meant to adjust the needle the carb had to be ripped out or turned on its side and fiddled with using prayers and a magnetised screwdriver you only had to remove the tank to do the latter. Another slight nasty were the crankcases which, to help keep the bike’s mass down to around 300lbs, were made from a magnesium alloy which is marginally lighter than aluminium, but vaporizes on contact with salt...
On the road, all is as you’d expect. After running in, all 32 horses seemed to be on parade and the acceleration was pleasantly brisk. This one really will pull from any revs, but the primitive chain transmission with cush drive in the rear wheel hub snatches, if you stretch a point, and stretches the chain.
Over 60mph it begins to lighten up at the front, but a 90mph bash up the motorway was no problem, apart from hanging on to the wide bars. Cornering on a Dunlop Trials Universal rear and Mudplugger front was predictable, rather like a flat tracker with plenty of understeer and no sudden sliding. I imagine that the new kinds of trail/road tyre from firms like Metzeler would allow you to get the pegs on the deck with no trouser trouble. Which is more than can be said for the brakes, they were replaced with a disc on the later model for reasons that will become apparent to anyone who tries to use the drum at 90mph.
Off road, the XT is a bit of a tank, but I enjoyed it most on dry trails up mountains, when its huge torque allowed progress up any slope in second gear at zero revs. Luckily, no end of engine braking is available down the other side. The appearance of mud filled me with dread, however, as the inadequate tyres filled up instantly turning the bike’s lorry like bulk into a real liability. Decent tyres improve matters a lot; it’s well sprung at the front and Nitro gas shocks on the back are brill until they wear out.
Economy is no great shakes at about 60-70mpg, but bear in mind that you have to spin the motor a bit to really fly - driving with restraint improves that figure. Lighting is 6V and the bike will run without a battery. Try not to come off at speed as the forks and frame bend real easy.
A final word of warning to anyone contemplating an XT - spares are very expensive and difficult to find, there are next to no bikes at all in breakers and direct communication with the importers proved to be difficult. All XTs of similar age are likely to have the same thing wrong with them - the pistons and people tell me that the gearbox expires as well, though mine was fine.
The XT is a Jap classic - just as the CB750 introduced the idea of the transverse four so the XT re-introduced the big thumper, a class that is alive and well today. If you can find an original, unraced job for about £300-400 and don’t mind waiting for bits, go for its collectability. If you want a bike for everyday use, go for the later 550 or 600 with better carb and brakes, not to mention monoshock rear. The SR has the same motor but with an alternator, the castings are almost the same, but the SR has CDI in place. of the XT’s points. The units are otherwise interchangeable, although the SR motor is a wee bit heavier, and you’d have to either transfer all the ignition gubbins or fit the XT magneto (bolts straight in) and fit the points to a modified clutch cover.
The overall picture is of a pioneering design; the first of its kind from Japan, and one whose popularity exceeded all expectations. As a result of the clamour for the original, Yamaha felt encouraged to proceed with development enter the Paris-Dakar race, and the rest is history, not to forget Honda, Kawasaki et al turning out equivalent bikes.
Paul Calomen