The Yamaha 750 twin looked rather forlorn in a far corner of the dealer's showroom. The faded orange of the tank merged strangely with the rash of corrosion. It had just come in from the States. They hadn't tried to start it or anything, mine for £750 if I wanted to take a chance on it. Dead battery but plenty of pressure on the kickstart. Even the UMG didn't list any details on the 1973 machine, so it must be special! I'll have it.
Yamaha started to make big vertical twins in 1971, with the 650 XS-1, which soon became the XS-2 and then the XS650. A brilliant, tough engine but a rather hopeless chassis. The TX750 came out in 1972, one year before the XS500, with which it shares its basic layout - though not one single engine component. The XS500 had an excellent chassis but dodgy engine. So to the big question, was the TX going to have the best or the worst combination of the two?
Before I could find out, I actually had to get it running. The clock read only 18000 miles, so things were promising. The battery was dead and the wiring didn't look too fresh. It's impossible to find any manuals or info on the TX750, so I had to go back to first principles. After a bit of direct wiring, a new set of spark plugs and connecting the bike up to my car's battery, I had two nice fat blue sparks. New oil was lovingly added to the cleaned up engine and a secondhand battery of the same size squeezed between the frame rails.
After taking the fuel tap apart and cleaning out the debris, I even had a nice flow of fuel. There followed about a thousand kicks. The engine kept making promising noises, caught once or twice then died. The final solution was to heat the spark plugs over the gas stove, rush out with the red hot plugs, whack them into the engine and go mad on the kickstart.
Finally, she came alive on the kickstart. I climbed on board. Big, wide bars, forward mounted pegs, poorly shaped tank for my legs... which all faded into the background once I had a go on the throttle. The TX sports a short stroke engine that makes around 60 horses at 6500rpm. Once it hit 4000 revs, the forward urge snapped my neck backwards, the engine spinning to a dizzy ten grand in the first few gears before I caught up with it on the five speed gearbox.
Despite weighing 470lbs it was a bit of a mover. Combined low end grunt with high speed power in a way that was almost intoxicating. The engine was rather noisy, the balancer chain whirring away, the camchain rattling and the valves clattering. Below 2500 and above 7000 revs, vibration burst forth from the engine in a frenzy, the petrol tank feeling like it was moments off splitting.
Some of this was down to the engine bolts being on the loose side. The threads on two bolts stripped when I tried to tighten them down. I had to rush around looking for replacement bolts. All the valves were on the loose side but I didn't know the real clearances, decided to leave well alone. The camchain tensioner was tweaked. I didn't have a clue about the balancer system, so, again, left well alone.
Back on the road, it was very smooth in the 2000 to 7500rpm range, but a rough old dog outside those limits. Top speed was an indicated, if somewhat blurred, 130mph! Fuel worked out at about 40mpg. I soon had to buy new tyres, chain and sprockets, which did in any fantasies I had about running the bike on a low budget!
Handling was very seventies. Straight, smooth roads were alright but any bumps caused the damping to fail. The back end snaked and the front shook. The bike was all over the place on bumpy curves, but despite such nastiness it never degenerated into any of the fearsome speed wobbles of the XS650!
A set of used Girlings and some hefty fork springs were secured from the breaker. Much better, until the stands and exhaust dug in on the more severe bends. The bike shook horribly, lifted the back wheel off the ground and would have rolled off the road if I hadn't twitched it back upright. That very day I ground the prongs down and dented the exhaust. The latter would still grind away, but it was progressive rather than aggressive.
The front disc was a deathtrap. It may've been brilliant when brand new, but I doubt it. The solid disc had no ability to dissipate water off the pads, the lag was incredible and then it'd lock on viciously. In the dry, the disc croaked away then locked up solid. The most interesting moment was when the pads actually fell out! The only good thing about the disc was that it was identical to the XS-2's and I could still buy pads for it.
A couple of times I almost lost it all. Speeding along at ton-plus speeds down the back roads, I'd suddenly clock some cager without a clue about my closing velocity, and have to hammer the brakes to avoid death. The rear drum was also a feeble thing, so the whole bike would go into a desperate wallow, that gave me hardly any control over the final direction! More by luck - or was it divine intervention? - than any skill on the bike's part I avoided hitting anything.
One other curious thing about slowing down was the way the gearbox would bang down through the gears - more often than not locking into a false neutral! Normal changes were okay as long as I took it slowly on the change and pulled the clutch lever all the way back for a moment. The latter had a lot of chatter at tickover and a vicious take-up, but I soon became used to it.
After the first few weeks I was pretty pleased with the machine. It was fast, made a lovely roar and handled okay. It was also narrow enough to chuck through the cages in town and if wound up to ten grand would do spectacular drag starts! I could even get the front wheel up in the air if I gave a strong tug on the bars, though there was a chance that it'd come down at an angle and I'd have to get my boot down to avoid the dreaded tarmac rash.
One of my friends had an old TZ250 Yamaha racer in bits. This had a massive, double-sided TLS front brake, that took up most of the wheel. This was an eighteen incher whilst the TX had a nineteen inch rim, but the spindles were the same diameter, so I thought I'd give it a go. The TZ weighed almost half the TX's mass, but the drum was set up for fierce braking, which with the extra mass was sufficiently soft to suit road riding. The drum was brilliant, burning off speed and stopping the bike wandering off to the left. Also no wet weather lag. It's interesting that in the early seventies the TZ's had this drum and not a disc, like the road bikes!
After three months and nearly 2000 miles, the vibration came in really strong at all revs. At this point I must admit that I liked winding up the bike way into the red zone. There didn't seem to be any limit in the first three ratio's! When the vibration came in heavy I was working hard, didn't have time to suss the engine. Half a week later, there was a grotesque grinding noise and then the bike locked up solid. It sounded very expensive.
The crankshaft had broken, probably because the balancer system had worn and started reacting against it. Given that massive neglect of the engine was involved, this shouldn't put you off the bike - the lack of information and spares, should, though! On the road, the bike's a bit of a buzz - and you can take that any way you want!
As the chassis was still okay, I squeezed in an RD350 engine, with wild ports. I now spend most of my time on the back wheel.
Dick Williams