Monday 8 July 2019

Suzuki GT750


My Suzuki GT750 did not come from the factory but from three different rat bikes, each costing less than a hundred notes (some five years ago). One bike, the eldest and highest mileage (1974, 59700 miles) still ran after a fashion and was thrown into my commuting chores for a couple of months. The water-cooled, three cylinder motor would only run to 5000 revs - down to a combination of engine wear and expansion chambers with open carbs.
 

The chassis was horrible, the frame slightly bent and the suspension sagging on its springs. Rather than curse the lack of speed I was thankful for its slowness - it kept me from falling off too many times. Starting involved pushing the heap twenty yards, throwing myself on the seat and hoping it would bump into life. Even with some quite essential bits junked (they had rusted away or just fallen off), the beast must've weighed near 500lbs. It was a strange and vicious way of keeping fit.

Running through town I was the centre of attention due to the racket out of the exhaust and the various bearings and pistons complaining about having to carry on working. I wrestled with the bars, throttle and gear lever trying to keep the bike on the desired path, about the only thing that worked well were the brakes. So well did the front discs operate they put the forks down on their stops, all twisted up with the tyre screaming for help as it skidded along the road.

A week or so was all I needed to become used to the monster. I was used to old Japanese hortors and was becoming strangely attracted to the exhaust howl and the way the bike carried on forward regardless of the fact that it gave every sign of seizing up and falling apart. When the engine finally locked up I was impressed enough with the bike to look for another.

I had already made some contacts, GT750s are rare enough on the road to allow owners to chase each down and exchange anecdotes. Despite the state of my bike I'd had two offers for it from owners looking for a spare GT. A few phone calls got the word out that I was looking for another Suzuki and about a week later a totally worn out GT750 turned up, a 1976 version this time.

The frame was straight and there were a couple of electrical and engine bits that were salvageable. The cylinder bores were OK, so I used the other pistons with a new set of rings, the pistons being oversize in standard but worn bores. The only thing I could do with the crankshaft was exchange it for a rebuilt one. One gearbox had reasonable selectors, the other good gears, so it didn't take much thought to combine them.
 

That just left some better suspension, which the local breaker was happy enough to provide from a GS750. Some hammer, chisel and paint work saw the bike back on the road. This time it would start on the kickstart - after six or seven kicks. After a couple of months I found myself running to fat, so used had my muscles become to the bump start. Handling was never what could be called taut, the GT wallowed and weaved, twisted and thumped every time the speedo reluctantly went beyond 75mph.
 

Speed wobbles were not entirely absent, either, usually coming in at 90 to 100mph. I always thought that it was the dizzy engine vibes come 7500 revs that was turning the frame to jelly, thus disconnecting the headstock from the frame - well, that's what it felt like. After a couple of months, when I decided that the motor wasn't about to explode, I took some thick steel plate and welded it around the headstock and swinging arm. It pushed the wobbles up to 110mph, which was all what were left of the GT's 60 horses could manage.

The first bike would do only 25 to 30mpg, so when the second one turned in 35 to 40mpg I was quite pleased... in reality, given its poor performance I should've been getting twice that. Other running costs were minimal not because nothing wore out but because I always stuck on the cheapest stuff I could find from breakers.

I became a known face in the two local breakers, so when one was offered a GT750 which he didn't want my phone number was passed on. This was seven months into ownership of the second one with no on the road failures. This 1978 model looked tired, didn't run and had a lot of dents in the cycle parts. Its only good point was cheapness.

The plan was simple enough, use the new bike with my existing stock of-parts to build a second engine. In a moment of weakness I convinced myself that I should tune it up! Thus high compression pistons, enlarged ports, secondhand racing carbs and a set of expansion chambers to replace the rusty 3-4 standard system I had rescued from the second bike.

By the time I'd finished, after about six months of pissing around and offloading a pile of dosh. the existing engine was misfiring at high revs and feeling like it was about to seize up. This wasn't as bad as it sounds, the bike had been thrashed around the Continent for three months in the company of some mad nutters on equally aged but much faster big Japanese fours. 100mph cruising sessions practically had the crankcases melting down and I wrenched my shoulder muscles keeping the GT within one lane of traffic.

So, it was out with old and in with the new. What a lovely howl the triple makes on spannies! I'd stripped most of the junk off the GT, probably got its wet weight down to 475lbs and fitted a much modified Z1100 front end when its owner conveniently blew up his motor - we told him not to fit a turbo-charger...

I was expecting a lot from this reconstructed motor, I'd put enough effort into it! There was no power below 5000 revs, then a 1000rpm's worth of stuttering and then a fantastic hard edged howl as the GT hurtled forward at a startling pace. I knew I'd done something right when the front wheel reared up almost vertically. Power ran out at 9000 revs when the vibration threatened to split the petrol tank in two!

I played around with the carbs, trying to get it to run at lower revs, but all I did was end up flooding the motor with an excess of petrol. The bike was so bad in town that I had to buy a rat GT250 for commuting to work. Many highway jinks followed on the bigger Suzuki, which included putting 130mph on the clock on one stretch of empty motorway, only to find the damn thing weaving over three lanes of highway. I put on some HD shocks and did some more frame bracing, which seemed to work a treat.
 

Meanwhile, the other engine had another rebuild to stock tune except for a little bit of file work on the ports. Parts were becoming rarer and more expensive whilst running bikes were advertised at silly prices. One advantage of the GT chassis was that it was large enough to house any number of stroker engines, so if GT750 parts ever do dry up completely I might fit an RD motor or something.

Of course, the durability of the tuned mill is just good enough to take you from one end of the country and back again - don't ask! I arrived back home from this epic burn with rumbling main bearings and a crotch full of petrol from where the Araldite repair had started to leak!

For the past year or so, some 14000 miles, I've been using the stock motor which seems to be good for 20000 miles between rebuilds even when it's thrashed and neglected. One of my mates recently paid £1500 for an immaculate, 3000 miler in completely stock condition and we have great fun trying to burn each other off. GT750s are interesting bikes, way off the pace, these days, but fun to own and ride all the same.

Mike Slough