I have owned my W reg Suzuki GP100 for longer than I care to admit. This little stroker has, on the whole, provided sterling service. It's not very fast, about 70mph flat out on a good day and there’s not much action below 6000rpm. Mileage has steadily increased until now the speedo boasts 63200 miles.
At 37000 miles a new barrel and piston were fitted, which rejuvenated the performance, it having tailed off to a top whack of 55mph. The small and big ends were still OK. The only other major problem to date has been a burnt out clutch. I went through a period when I found it great fun to wheelie at every opportunity. The only way a GP will wheelie is by a combination of massive clutch abuse and maximum revs. The consequences were going to be obvious.
This might suggest that the machine has been mercilessly caned and abused. Well, yes and no. I have always ridden the bike at full welly whenever possible but I have also been meticulous about checking the engine oil level and regularly changing the gearbox oil. Things like ignition timing and carb settings hardly ever seemed to wear so were left alone until a noticeable demise in performance occurred.
I really do believe that the GP100 engine is a very tough little nut. Of course, there are ways of breaking it. A friend with a similar bike went to great lengths to tune his GP up. The result was a banshee wail, huge clouds of pungent smoke and a top speed of 75mph. The engine, which had the head shaved, the ports enlarged and an expansion chamber fitted, lasted about two weeks before the piston rings snagged on the enlarged ports, sending a trillion pieces of ring circulating around the motor.
That’s the one disadvantage of the commuter hundreds as opposed to the race replica 125s once you pass your test there is no easy way on the smaller bikes of extracting extra power. I have been tempted on several occasions to modify my bike, usually when I've been burnt off by some lout on a derestricted 125, but have so far resisted such suicidal urges.
Probably just as well when you consider that the chassis is not up to much. The frame is similar to the much maligned Tiger Cub in overall layout and shape. It is probably very cheap to make, which is its one virtue. Beyond 60mph, even with newish suspension, its limits are pushed. Signs of stress are the way the bike bounces about and weaves around, even in a straight line on a smooth road.
Of course, the suspension doesn’t stay in shape for very long. The front springs soon go soggy and rear shocks do a reasonable rendition of having absolutely no damping. If you're lucky enough to find a machine with forks that are not pitted or rusted, cover them in grease and fit gaiters immediately. Once a bit of rust gets hold it rapidly spreads and wrecks the fork seals - not that there was much damping to begin with.
The forks are relatively easy to sort out - take ‘em apart and fit some washers on top of the springs. Thicker damping oil also helps if the seals are in reasonable shape. Replacing the shocks with just about anything the breaker has on offer is a good bet. Thus replete, the ride will be a bit bone jarring but there won't be any speed wobbles right up to the top speed.
At least not until the cheapo swinging arm bearings start to go. Support for the swinging arm is pretty minimal to begin with and under hard going it's not unusual for the back wheel to take a walk for a few inches. When some slop develops in the bearings the chassis turns real vicious... it feels like both tyres have suddenly deflated and you're riding over a series of sleeping policemen (oh for such a chance!). This happens every 6000 miles or so. Despite using half a tub of grease during reassembly, the spindle is a real bugger to remove and often ends up so bashed about that its replacement is required. I tried to get some phosphor bronze bearings made up by the local engineering workshop but they had a minimum fifty quid charge, so I just have to suffer frequent changes.
Another often replaced item is the headlamp bulb. Electrical output is related to engine revs. At low revs the headlamp is a dim glow and the engine stalls if you put the indicators on. Revving the bike hard in lower gears produces a relatively bright light but going too high up the rev range causes the bulb to blow from an excessive frenzy of engine vibes. Very clever.
In fact, the lighting systems of many small commuters are so poor that they are a danger to the rider and other road users. There surely should be a minimal standard for all road vehicles... the government wastes its time and our money trying to outlaw motorcyclists with stupid laws yet can’t be bothered to insure that all motorcycles come with proper lights. How bloody minded can you get?
The GP has other minor problems that adds to the fun. The seat soaks up water like a sponge, which in turn causes the base to go rusty. The steel mudguards also turn to rust after a couple of years. Chain and sprockets don’t last more than 7000 miles a set - I couldn’t believe this on such a small bike.
The engine sprocket is tiny, which doesn’t help at all. The drum brakes are not really adequate if you ride at top speed everywhere, but below 50mph they pull the Suzuki up with surprising effectiveness. The shoes go for about 15000 miles. Whatever problems I've had with the Suzuki have come one at a time and have been easy and cheap to repair. Various stripped threads have been bodged with Araldite. Plastic guards and a GRP kit for the seat base have taken care of the major rust spots. Some additional rubber mounting on front and rear lights have stopped them blowing, whilst the indicator problem was solved by their removal.
Perhaps, most astonishing, I've never fallen off the GP100 in all the years I've been riding the thing. As it commutes through the winter, this says a lot about the basic stability the bike offers. I always use decent tyres rather than cheap imports which makes a major difference. I have come close on many occasions, but the bike is so light that it can be thrown out of the way of offending cars with absurd ease.
On a couple of occasions, I've had to put my foot down and do a speedway style broadside to avoid plunging into a car. The bike twitched violently but succeeded in avoiding metal carnage. On others, I've run the bike off the road, skidding along grass verges or shooting up on to a convenient bit of pavement with a frame shuddering crunch.
The GP is absurdly easy to filter through city traffic and just fast enough off the line to keep most cars in their proper place. Country lanes are OK as long as they are not too bumpy. Faster roads turn into a monotonous drone and after 75 miles sheer agony as the seat foam flattens out. Using the pillion rests on the swinging arm helps a little to relieve muscle tension. However you ride the bike, it does around 60mpg, which whilst not brilliant for a commuter is acceptable as major outpourings of money are very rare. Presently, the engine has started to rattle a bit which sounds like the small end to me, or it may just have worn out the bore and piston again. I will probably fit a newish engine out of a breaker rather than try to repair the current one. Or I may just buy a nearly new bike and keep my old one for spare parts.
As a commuter it's hard to beat, although night time riding is perplexing at the best of times (but that’s probably true for its rivals as well). They are bought either by commuters or learners, the latter are obviously best avoided. Prices start at about £100 for an old one that is still running, going to around £750 for a nearly new one in immaculate condition. Demand is high for good ones, so you need to turn up on the night of the advert with the cash to hand. A good one is definitely worth the effort.
Bill Laird