Wednesday 3 February 2021

Suzuki GT500

In the summer of ’84 I contracted this infatuation with a Suzuki GT500, the emotion was every bit as strong as lust. I soon learnt not to confide my longings to any friends, because the universal response was, "Uck! A two stroke! They never start, and when they do they make an ‘orrible noise and lots of smoke... you really are mad." This last was invariably said in a tone of voice that clearly revealed that I had previously been placed at the extreme edge of acceptable eccentricity. The most charitable response I was to receive was from a steam train enthusiast, who diplomatically hid his expression behind his beard, and after much deep thought, suggested that perhaps we ought to have another pint. There was also this slight problem, I didn’t have a motorcycle licence...

The steam train enthusiast recommended I buy a step-thru to take the test. Maybe I’d have been wiser to have gone for an MZ. That way I just might have been successfully diverted down the MZ route, and thus avoided the astronomical expense of what was to follow. That autumn I eventually found what I wanted and £250 changed hands. My only reservations were that this 1978 GT500A had rearsets and extremely anti-social expansion cans. It spent that winter in the lock-up, having its cycle parts refurbished. Since the motor and gearbox appeared OK, that lump was put in the corner under newspapers.

Under the smart tank cover was the inevitable rusty dent I could have chosen between having the dent raised and the tank resprayed, or buying new and paying off the national debt of Mexico. At this stage I got lucky by finding a perfect, brand new tank from bankrupt stock for £32. The seat had never belonged to the GT, in fact, it looked like it came from a smaller bike.


Much searching only produced rusted out replacements, so I gave up and paid £70 for anew one (gasp of editorial horror - Ed). Stock pegs and pedals were obtained from breakers, although it added heavily to BT profits and produced eye Strain reading through MCN classifieds (the size of the print would have given lawyers a second thought).

A load of chrome plating relieved me of £76. Everyone shies away from chroming due to the expense. This need not be the case as the cost is related to the area of chrome plating. The rear mudguard thus cost over half the bill ( should have painted it), but the pedals, down pipes and bits & pieces were not bank breaking. The down pipes were superb silky smooth, fluid curves of perfect chrome.

The frame went away for epoxy coating (£63 including transport) and the finish was excellent but they had connected one of the electrodes to an engine mounting which had arced and messed up the lug. When dismantling the bike, I took extreme care to label all the electrical connections prior to removal of the wiring loom.


I even went to the expense of buying a Dymo machine. When I had finished, the loom was suspended from nails along one wall of the lock-up, looking most professional with all its brightly coloured little labels. Not quite so professional on close inspection due to the labels reading "to grey box behind battery case," and, "from funny engine connector," etc. One morning, following a particularly severe frost, I opened up the lock-up to start work and discovered that autumn had come to the Dymo tree - the Americanism, Fall, might be more descriptive, for ALL the labels were sprinkled along the floor beneath the loom. The non-frost-resistant glue on the labels cost me weeks of extra work trying to figure out where all those invisible electrons were supposed to go, and at least five years of grey hair.

I obtained original silencers from a breaker, only to discover that the insides were rusted out. I should have guessed. They're called breakers because they break your heart... isn’t life fun? The outside casings will never rust through because they were designed by a naval architect - the metal is an eighth of an inch thick, which may explain why the bike had such a nice low centre of gravity.

The problem of the exhaust must have been solved during a session in the pub with the steam enthusiast, because I decided to buy tin-snips and a welding kit and do the job myself. If there are any logical arguments for attempting this undertaking I’d like to know what they are... inebriation is not one of them!

I borrowed and bought all the books about two stroke exhausts that I could find - and there are lots of them. Some of the books had clearly been written before the time when an understanding of what goes on inside a two stroke exhaust had been achieved, whilst others were written by hobby mathematicians, requiring access to computers, floppy discs and all that junk. Which was all very well, but I wanted exhausts that worked, not some fancy geostational orbit.


If, like me, you should ever suffer from brain failure and decide to have a go do the following. Study and read Performance And Tuning In Theory & Practice - Two Strokes by A. Graham Bell - by far the most practical book. Cultivate masochistic leanings because you will need to enjoy pain and frustration.

After The Cutting Of Metal and The Rolling Of The Cones for the expansion cans, came the final production, The Welding Saga. If you’ve any sense at all you'll use a MIG welder (even a monkey can use one, and a trained one might get the products of his labours in the Tate), but if you are like muggins, you use gas, thus needing the patience of a saint and the fire fighting abilities of Red Adair.

There is no big problem in making one silencer, that’s merely a case of pure determination. However, the real problems start when you try to make the second one. Not only does it have to be an exact mirror image of the first, but also perfectly symmetrical when mounted on the bike.

Finally, all the parts went back together where they belonged. The two part test was passed and the step-thru sold. To my eyes the Suzi looked fantastic and far more desirable than the latest water-cooled, fully faired whizzomobiles. Amazingly, everything worked first time out, and, wow, what incredible power. From having been unable to crack the elusive 50mph barrier to the sudden and  sobering sight of the tarmac blurring past at eighty on the merest whiff of throttle, was a sufficiently potent incentive to spend the step-thru money on some leathers.


On my first long run I decided to open it up to see what it’d do. I had just got a ton up on the clock when I realised that all was not well behind... all four lanes of: the dual carriageway were obscured with dense white smoke. Either the Red Arrows were practising low that day or I had problems. Turned out that the crankshaft oil seals were worn and the gearbox oil was sucked into the crankcases. Since the smokescreen only occurred at high revs I went all summer like that, whilst being very careful to top up the gearbox oil before every ride.


The home-made silencers proved to be excellent, fulfilling all of my design requirements, which were that a minimum of noise should be made and a maximum of midrange grunt produced, as I wanted a bike for touring not street racing. There was only one slight flaw in this brilliant piece of design work - the noise came out through the sides of the the expansion chambers. This is why the original Suzuki silencers were made from the hulls of scrapped battleships. You could squat down behind the bike and have someone rev the motor and there were no painful noises. But, when riding the thing with the throttle wound on, as soon as it hit three grand the most amazing harmonic roar began. It was like a mixture of fog horn and a cathedral’s organ at full chat. It really turned heads and gave the bike immense presence.

Winter number two: SEP of Knegworth overhauled the crank. They are highly recommended and said that the mains on the GT last forever, once in a blue moon a big-end needs attention (due to crazed right hands) and crank seals wear out usually if the bike’s not been used enough. The oil drains off the seal which is then sitting on the dry metal of the crank, first turn of the crank removes one thou off the knife-edge of the seal. Do this often enough... they have had GT cranks in for new seals at 80000 miles and have found that the mains, rods and bearings are still serviceable.

On the road, the bike was stable in a straight line all the way up to the top whack of just over the ton. However it wasn’t too happy in the corners. Maybe a fork brace and modern shocks would have helped? Two things it hated were the cold planed surfaces at road works and wiggly tar joints along the road.

It averaged 50mpg and used about one pint of oil every 400 miles. It always started first or second kick, except when an elderly ex-Scott rider asked me to demonstrate this feat. Then it reduced me to a sweating wreck before firing up. I had the impression that the ex-Scott rider found this mildly amusing; I bloody well know that the Suzuki found it hilarious. A Goodridge brake hose made a huge improvement to the single front disc. Rumour has it that further quantum gains can be had by fitting a Yam LC master cylinder.


GT500 and T500 cranks have different nearside ends, different ignition systems and coils so don’t buy without knowing what you are getting. On the GT the plugs both fire together, giving two sparks per cylinder per revolution. One at BDC and the other at TDC (well, about 24° before it if you're being pedantic). I know it all sounds most unlikely and a bit Iron Curtain-ish, but that’s what it does and it works very well indeed. If you want a slow idle speed fit platinum tipped plugs - NGK B7HV.


If you make a conscious effort to change gear smoothly and don’t do stunts like wheelies, the chain lasts. well. I lubed mine often and it hardly ever needed adjusting. Rear tyres go for about 7 to 10000 miles and fronts a lot longer.


If you have empathy with strokers and are orientated towards the touring end of the spectrum, get a GT500. It was a really good bike and sadly underrated in its day. As time goes by I get to thinking that if I were to win the pools, I’d search her out and buy her back. Then, I’d fix up the cornering and maybe have some fun grafting on a reed valve conversion.

Marc Sivrac