You don’t see a lot of Yamaha XJ750s about today. When a 1983 example turned up for £675 in the local rag I was first on the doorstep, tongue hanging out, palms sweaty and the money burning a hole in my pocket. Well, for that kind of money you don’t get many shaft driven, 80hp DOHC fours, do you?
This was a year ago, then the Yamaha was in reasonable shape for a 47000 miler with three previous owners. Even sported an original if patched and rusted exhaust system. The Roadrunners were only fit for melting down into Russian condoms but the rest of the machine had an air of being well cared for even if the original paint was faded. Original service dockets indicated that its past had not been entirely misspent and there was even a full set of MOT certificates showing its gradual increase in mileage.
The combination of original twin shocks and bald tyres did not inspire much confidence in the handling. The front forks were OK but needed filling up with air every other week, although the anti-dive clanged away uselessly, not stopping the forks bottoming out under harsh and frantic use of the twin discs. The front brake was to reveal itself as a good stopper, predictable and powerful, not too badly affected by wet weather and only requiring a clean up every time the pads were changed (every 8-10000 miles). Of late I've noted a strange whistling noise and that the discs have become very thin, so great expense is probably on the way.
Much fun was had on the ride home, throwing around 500lbs of skipping, hopping, sliding iron on damp roads. I did gain the general impression that the tubular trellis bore more than a passing resemblance to a frame, for however frantic did become the tyres and suspension, the bike never ran right off the road nor got so out of line that clenched buttocks and a death grip were insufficient to pull the XJ back into shape.
But then I do weigh fifteen stone and have enough muscle to make sure than no-one pisses around with me. Fitted with wide, high bars I needed all that muscle to fling the bike through the long series of S bends that were part of my favourite route. It was such a great run than I often awoke an hour early to take the ever so long way into work - the temptation was often high to ride straight past the office gates, heading off into the great unknown.
First thing, then, a new set of Roadrunners. Disappointing tyres, I found, as the bike remained highly sensitive to white lines and never felt entirely relaxed at high speed. When the rear wore out after only 4750 miles, I next tried a set of Metz's. Much more suited to the Yamaha, this Teutonic rubber, but the set was worn out in less than 4000 miles! Stable up to about 90mph, thereafter the Yamaha took on all the qualities of a carthorse on an ice-rink.
On several occasions I thought we were going to end up in a ditch but somehow the combination of my desperate muscles and the XJ's frame pulled us out of full suicide mode. Even when the chassis was fully wound up from extreme survival antics, some stability remained.
Rapid tyre demise resulted from high speed take-offs and rubber scorching braking manoeuvres, I think, the latter necessary to avoid running the bike off the road when screaming up to corners at highly illegal speeds. Wheelies were possible but hard to control, more often than not the bike coming down on the front wheel with a sickening crunch that had the forks down on their stops. I soon gave that game a miss.
The Yamaha doesn’t like going into bends on the brakes, by the way, like that other shaftie, the BMW boxer, it prefers to be set up on line and then powered gently through the corner. Unfortunately, that isn't my riding style, even a year on the XJ has failed to modify the juvenile delinquency that overcomes me whenever I'm astride a motorcycle.
The XJ750 isn't particularly sensitive to having the throttle wound off when banked over and it's even possible to take a dab at the indifferent rear drum brake. The back brake has not required replacement of its shoes, they are probably original, so lacking in retardation qualities is the drum it’s hardly worth using other than to balance the bike under harsh braking.
Quick directional changes tend to leave the suspension several plunges behind, as well as my stomach, but a newish set of Konis sort of sorted the back out - the ride is a bit harsh, the bike rumbling over the corrugated road surfaces with which this fair isle is blessed. Abuse of the throttle in the lower gears will still put the machine seriously out of line in the bends, but a bit of restraint allows the beast to run through the curves at a reasonable pace.
I don’t know how many of the original eighty horses the XJ still kicks out, but it still comes on cam around six grand very strongly. With the rusted silencers, carburation was not very clean below 5000rpm, with a lot of backfiring and stuttering. When the exhaust finally corroded to the extent that it was only hanging on by a few inches of steel, a Motad 4-1 was fitted. I had allowed a whole weekend for this process but the old exhaust fell off with a few taps, even the header bolts were not seized in and the Motad went on in a matter of minutes!
This certainly looks and sounds the business but there is a big dip in power between 3000 and 4000rpm which makes the bike difficult to ride smoothly through town. However, it's now quite capable of pottering along at 2500rpm in any gear you'd care to select. Indeed, once out of town there’'s not much need, save for the flat spot, to play around with the gearbox.
Despite now having 67456 miles on the clock, the gearbox and clutch are still slick, better than many a new bike! Perhaps changing the oil and filter every 1000 miles has helped! Other maintenance has been minimal - no changes in valve shims needed (there are only eight valves) and the carbs have needed setting twice since I've owned the machine. The alternator and starter are hidden under the carbs which makes the motor very cramped around that area but provides an unusually narrow engine for an across the frame four of this capacity.
Lucky that, as I've dropped the bike at very low speeds a couple of times and managed to avoid any expensive damage to the engine. Despite the mild custom style which results in a low seat height, the bike has a top heavy feel below 10mph and can catch out the unwary rider, the whole machine flopping over rapidly if you get it wrong when doing a sharp turn!
There is no balancer in the engine and vibes are usually present to some extent. They attack the pegs to the greatest degree, usually once past the 80mph mark. A bit annoying as the motor is capable of pushing the hulk up to an indicated 125mph with a degree of indecent haste. The highest speed I've managed is 132mph! Not that it’s practical to cruise at such speeds, with the high bars and wobbly chassis. Whether new machines were similarly afflicted by vibes I could not tell you, it may just be down to old age.
Whether it’s the vibes or the age of the wiring system, I don't know, but the bike likes to blow bulbs and fuses whenever I go for a fast thrash of more than a 100 miles. On a couple of occasions I've had to ride home with no lights and fag paper in the fuse holder. I now stash a cache of fuses and bulbs on the bike. The battery went a few months ago, the machine refused to start without one, unlike old British bikes, even when pushed up the road. Starting was more normally a first press of the button affair, although a choke inspired tickover of 3000rpm was a bit disconcerting.
The XJ750 has a very reliable engine that even now shows no sign of flagging. The first thing to go will be the camchain and then the pistons, with the chain primary drive waiting in the background to cause serious mischief. Clutches are said to be dodgy but mine has bucked the trend; maybe it was upgraded in the past. As always, with Japanese engines, regular oil and filter changes are the key to longevity, something my machine has evidently received in the past. I would love to buy a low mileage XJ, but have yet to see one at a reasonable price!
Peter Daniels