My first idea was to buy a used pre-unit Triumph, do it up and rebuild it to running order... maybe even make it into a chopper (this was the seventies). As soon as I worked out the amount of toil and trouble involved in such an exercise my mind rapidly turned to buying a new British bike.
As this was about the time that Meriden had formed their co-op, I had the choice of various 750 Triumph twins, so in August ‘78 I bought a new 750 Bonnie T140V, full of tales from the brochures of a flat out speed of 112mph and the best of British engineering.
Of the two that I’ve owned that was the best one. I should never have traded it in for the other. It was quite a good looker too, a mixture of dark chocolate and maroon highlighted the lines of the tank and contrasted with the brown imitation leather seat, the glossy chrome and polished engine cases.
| don’t know of any other bike that could become so dirty as that Triumph. Five minutes on a wet road and it’s filthy. The mudguards are only as wide as the tyres, Dunlop TT100s which chuck off loads of water. I spent hours cleaning the bike up and even bunging on a mudflap did little to stop the deluge.
Keeping up with the maintenance wasn’t a problem, since I was already in the habit of sticking to a strict, disciplined maintenance regime, all year round in all weathers. Weekly checks every Saturday afternoon on the dot, monthly tasks carried out to the letter including re-greasing the swinging arm bushes (easy as there are grease nipples on the swinging arm).
The bike would cope with everything I threw at it, wet or dry. It would hammer along switchback country roads at 70 to 80mph, whilst it would drift the whole width of the road, bouncing from bump to bump. Physically narrow and light, it felt like a big bike should, yet was at the same time very easy to throw around. It handled superbly, the steering looked after itself, requiring very little rider input, just point in the general direction and it’d find its own way. The engine had plenty of low down torque - it could pull away in third gear - and bags of engine braking.
The brakes were viceless, and their efficiency improved after the chrome plating had been rubbed off the discs, or removed by some other means. A rear tyre lasted 7000 miles, same for the chain, although Izumi chains last even longer. Front tyres cracked before they wore out. Brake pads lasted 14000 miles or more.
The only thing that really spoils the whole plot is the motor. Unfortunately, this bit is rather important. It’s a heap of shit. An old fashioned design with one or two bodges thrown in for good measure. State of the art in 1958! At anything over 60mph it would drink oil at the rate of 250 to 300 miles per pint, not leaks, it just burns the stuff. There are only four pints in the frame reservoir.
After every run where the motor got properly warm, the ignition timing would be all over the shop, because the backplate slips. The run back would have the motor feeling harsh and horrible - fitting toothed or star washers in place of the inadequate lock washers beneath the backplate. screws helped. The exhaust header pipes are merely hammered into the head and always come lose, the finned clamps are only there to look pretty - drilling holes in the cylinders and inserting thick wire helps.
The cams used in the 750 didn't really suit the displacement or the exhaust system, resulting in a massive flat spot just where the motor was beginning to get interesting. Even more amusing, the spark plugs keep coming undone and will eventually fall out. The oil in the primary chaincase emulsifies in the winter and has to be changed every other week or the primary chain and clutch wear out quickly.
The motor should never have been taken out to 750cc. Apart from the enhanced vibration problems, the cylinders are so close together that there’s not enough meat for the head gaskets to seat properly - the plain copper ones are hopeless, only factory originals work. The two important cylinder head nuts - which need an unusually large Allen key, by the way - are a pig to reach, being right in the middle and inside of the rocker boxes.
Nearly every accessory I bolted on was destroyed through the vibration. On the first bike, the T140V, driving lamps snapped their brackets, a metal RAC badge cracked right through and fell off, an air horn kit expired. On my second bike, the T140E, electric start Executive, a Polaris fairing, Cibie light and luggage all fell to bits. Cameras, tape players, radios and some camping gear were all wrecked when I foolishly tried to transport them on the bike.
I'm not through yet, there’s more. I haven’t yet mentioned the riding position, which I found pure purgatory. It’s much too upright, putting strain on the spine. The occasional backache trouble I still have now, I put down to four years of riding those Triumphs. And after an hour, the seat compresses until you feel like you’re sitting on the frame rails.
Why did | keep bothering with it all, you may ask? For the simple reason that the rest of it is so good. The actual chassis was brilliant. But the motor was naff for any serious long distance work. A 750 Bonnie will be quite OK for sunny weekend day trips and the like, but touring trips ask too much of the machine. Every day you have to tension and lubricate the chain, re-tighten the spark plugs and add a pint of oil.
There were only two problems I had with my first 1978 T140V the rest you could learn to live with. One was that an induction leak developed between carb and cylinder head - it turned out that both stubs had the wrong size O-rings fitted in any old how. The other problem was that the rectifier simply melted away - the actual diodes might be modern, but the mechanical design is naff. I replaced it with a silicon bridge rectifier block incorporating a metal base as a heat sink - available from all good electronic shops (ask for 12V/25A).
As I said, I shouldn’t have got rid of it in exchange for the 1980 Ltd Edition, red and black, Executive, which had major faults. The bike had electronic ignition and fuel system changes to cater to the stringent American emission laws. The revised carbs never sealed with the air filter box properly, resulting in grit damage to the valves and seats - it always ran too lean and too hot, pinking like buggery on a hot day.
The cylinder head cooks the carb mounting rubbers, causing them to disintegrate. The air filter intake was perfectly placed to suck up all the road grit thrown up by the rear tyre. In addition to all the problems in the earlier bike, the tappet adjusters chipped lumps out of the ends of the valve stems. It broke its original, and second, and third revised sprag clutch support spindle, part of the electric start gear train. The spindle snaps in half, bronze bushes work loose and teeth disappear from the gears.
The ignition amplifier failed because it filled full of water, thanks to its placement where the rear tyre can throw all kind of rubbish at it. The frame rusted away quicker than I could touch it up, and the rest of the bike quickly became shabby, whilst the original exhaust had assumed museum piece status covered in grease in the shed, the bike fitted with a 2-1 Piper instead.
Despite repeated and careful engine rebuilds - I spent more time in the shed than anywhere else - it blew up twice. Once coming home from Belgium and later when trying to reach the Isle of Man. I had my money’s worth out of the RAC that year. The cylinder kept coming loose, leaping up and down, a deluge of oil over the engine. Then there was the minor matter of holed pistons - either a cylinder head fault or plain bad design.
It soon became apparent that the 1977/78 Bonnie was a much better buy than later ones. The Executive was sold as a van load of bits as a rebuild project for a mere £400. I went out and bought a Moto Guzzi Spada...
Mike Holmes