My Suzuki GS750 was a composite of many different parts, having come to me in a pile of crates, as an abandoned chop - without the chop bits as they were used elsewhere. The engine was stock and in good nick (I was assured) and the frame was straight and bright red. The rest was up to me, sourced from various breakers, friends of friends and my own stock of parts. The odd bit of engineering work was done by a friend who had converted his basement into a workshop.
It was quite an interesting way of resurrecting a motorcycle. Pick and matching bits to suit my own needs, so that I ended up with S & W shocks, a GSX1100 front end, a tank off a GS1000, a seat from something totally obscure, etc. etc. What I wanted was a mean, lean look with a minimum of mass and maximum of suspension rigidity. At times I felt quite righteous, for instance, dumping the whole dubious, self-destructive Suzuki electrical system. As the bike came together my excitement grew until one sunny morning it was time for my first ride.
The GS750's engine is an eight valve, DOHC four cylinder unit that makes 70 horses, most of which is absorbed moving the 500lb bulk of a standard machine. I figured my bike was 50 to 75lbs lighter but it was also over 40000 miles old (going by the last MOT certificate as the original clocks weren’t available), which was rather more than just run in even for a generally tough old mill like the GS750.
The roar out of the Motad was music to my ears, the rustle of valves sounded pleasant and the engine revved around the tacho without any hesitation. I wasn't too sure what I was expecting, but the motor picked up cleanly from tickover making a smooth take-off so easy that not even a sixteen year old novice straight from an automatic moped would mess it up. The gearbox clanked a bit but went into second and then third without any hassles. Winding back the throttle, the rev counter touched 6500rpm then went completely berserk, bouncing deep into the red.
Wow, there, I screamed, as the GS tore up the road, only just avoiding cutting an apparently stationary cage in half. At least I'd found that the twin discs could scorch the tyres. The engine revved like crazy even in fourth and fifth gear, once into its power band there was nothing that could hold it, not even the deliberately tall gearing I'd fitted to give me a relaxed time when touring.
The next time I'd saw the previous owner he admitted that the owner before him, now that I came to mention it, had fitted an 840cc big bore kit with high compression pistons and high-lift camshafts. That explained how the bike had blown off my mate’s CB900 so easily that he had been sent into a flurry of spanner wielding trying to suss out what the hell was wrong with his engine. It was a useful combination of tuning elements, the big bore kit increasing torque at low revs whilst the cams and pistons turned the motor fierce when the power really started to flow in.
With the modified gearing I was getting 100mph at dead on 6000 revs, which meant when it went over the ton in fifth it suddenly picked up power and tore off down the road as if it was supplied with rocket fuel. It only quietened down a bit once past 135mph when the sheer aerodynamic drag of the naked bike and large rider overwhelmed the power so completely that it took a very long straight and an uncomfortably contorted riding position to put more than 140mph on the clock.
One rather unpleasant side effect of the increased bore size was vibration, even a stock GS not exactly being free of secondary vibes. The bigger pistons played their melody out just as power came in and so bad was their resonance that the higher reaches of the rev range could only be sustained for brief bursts of acceleration. That meant, though, that cruising at 100mph in top was fine, as the vibes had yet to gather their forces to any great extent. Due to the tall gearing, the transmission was unable to sustain speeds of less than 50mph in fifth and the top two gears were but rarely used in town, although there was no problem pulling off in first gear even up some pretty daunting hills with an equally large pillion on the back. An effective speed range in fifth of 50 to 110mph was fine by me as the torque would lunge us forward without needing to change down a gear or two to use the excesses of the power output.
With its mismatched suspension handling could've turned out pretty hairy. It was about an inch taller than stock which helped with the ground clearance but made it want to fall into corners. Also, if I was banked over and did something stupid like touch the front brakes the bike would shoot up to the vertical like a rat up a drainpipe, something that scared the shit out of me the first time it happened. By way of contrast, the rear drum could be used without trauma or the throttle backed off if I didn't mind the chain churning away on its sprockets (which might help explain a 4000 mile life).
Stability was never entirely reassuring. I blamed the slightly worn Avons at first, as the bike felt like it was running on only a few millimetres of rubber but a new set of Metzelers were, if anything, even more on edge. The non-standard suspension may have subtly altered the steering geometry but although it usually felt a bit tenuous it never turned really weird, taking speeds in excess of 130mph with just the slightest of weaves that not even hitting some quite violent bumps would turn into the kind of vicious wobbles that old Jap fours are famous for performing.
I guess a lot of its integrity was down to the stiffness, tautness of the suspension, which reacted well to large bumps but allowed the minor stuff straight through to my hands... having dumped the rubber mounting on the bars and pegs in search of improved feedback from the tyres. My last bike was so remote that the first I knew of a tyre sliding away was the heap going sideways down the road. With the GS I had rather an excess of information from the road and it took me a while to sort out the stimuli.
At the end of the day, after a month of hard charging, I had come to terms with the Suzuki’s chassis, could use it as hard as any bike I've owned, aware of how far I could take it before it bit back. Make no mistake, these old fours can turn as venomous as a cornered cat, but my GS750 was one of the better of the breed, coming stock with the most conservation steering in the business that not even my mods could shake.
It was a pity that the same couldn't be said for the engine. Two months, 2500 miles into the game, things began to go badly wrong. There was a noise in the engine like a ball bearing was whipping around. The bike still went as well as ever so I dismissed it as just a bit of clutch rattle due to the need to balance the carbs (the logic to which is obscure.....) although no-one else in our gang seemed convinced of that explanation. The real problem turned up 25 miles after it had first occurred. I was waltzing through town at 50mph in second gear when there was a deafening bang and then a screaming back wheel. I took a manful grasp of the clutch and rolled into the gutter.
The motor had thrown a rod, a gaping hole full of hissing oil and smoke in the crankcase. Pushing the dead bike home I had plenty of time to reflect on the chances of resurrecting the engine. When I totalled up the cost of a top end rebuild, exchange crankshaft and the chances of getting it right, it worked out cheaper to buy a crashed bike for its engine. This one had 52000 miles on its smashed clock and looked like it had never been touched by spanner (confirmed by the huge valve clearances but I had an excess of shims by then).
The contrast between the tuned engine and the stock one was massive. It was as if I was riding an entirely different bike. Its worn components obviously didn't help, but even that didn’t explain the meagre power output and paucity of speed, acceleration and fun. 110mph in fifth was pathetic for a 750, some 450 and 500 twins giving me lots of trouble in the back street races. After a couple of days it dawned on me that whilst my taller gearing matched perfectly the 840's power it was much too heavy going for the worn 750. A smaller gearbox sprocket had some kind of spirit back in the bike and had I not enjoyed the first engine’s excesses then I would've been satisfied with the machine but its new found blandness was too much for me to take.
The GS750 must've sensed my disaffection, for a mere 2000 miles into our relationship it started smoking like a stroker. The exhaust valves were shot, too many miles without a valve adjustment I'd guess. I put on the scarred head from the previous engine and rode around on the bike for a couple of hundred miles, as it was still useful for getting back and forth to work. Then I sold the GS before I ended up paying out any more money on it.
Overall, I just about broke even on the experience, but expended a hell of a lot of effort to put the original bike on to the road. GS750 engines are pretty tough in stock form, fun when tuned but not so reliable. The frame is strong with good geometry, most suspension will need replacing by now and the electrics are completely naff. I enjoyed myself most of the time but, these days, have moved on to a more modern Suzuki.
Jeff Stein