When I got my hands upon the machine. it was obvious that the four year old SP370 had led a hard life. The battered cycle parts, encrusted with dried mud, were all the evidence I needed to know it had been used hard off road. The owner was out of the country and his wife was determined to sell the wreck of the machine before he returned.
As the motor still sounded OK, despite 22000 miles on the '78 engine, and a quick run around the block produced no nasties. l was happy enough to hand over two hundred notes. As a bonus, the lady of the house dropped her shorts, and gave me a quickie over the best armchair.
The ride home was pleasant enough. I was not used to trail bikes and still think only a fool would willingly risk life and limb by riding a motorcycle off road. The SP felt very top heavy at first, and any slight input to the bars had the 300lb machine rushing off in the appropriate direction. The other thing that was a bit disconcerting was the way the soft, long travel front forks dived under braking, despite the fact that a puny SLS drum was fitted. I soon became used to both of these traits and was able to adapt my riding technique so that they were no longer apparent.
The other perennial problem with big singles, starting, was never a cause for worry with the SP. I had been brought up on British singles and found the normal starting technique of getting the lump just over compression and giving it a full bodied kick worked well enough to get the fires alight first or second kick, regardless of weather conditions or whether the engine was hot or cold. The only proviso was fitment of a new spark plug every 4000 miles. There is a sight glass on the cylinder head with a marker on the end of the camshaft to indicate the position of the piston but I never needed to refer to this.
The engine is similar to the GN400 and SP400. featuring a single overhead camshaft, two valves, gear primary drive and an absence of balance shafts. Vibration is nearly always present to some extent, but it is easily shoved into the background and appears to do no damage to either chassis or engine. Only when coming from a smooth four cylinder machine back on to the SP does it seem particularly rough.
The engine is best described as civilised in its production of power. This is no bottom end thumper that would delight Panther owners. nor is it a loud and rorty Gold Star imitator. There is only a small power step around 5000 revs, and although the engine never bogs down or conks out at low revs, it needed to drop down two gears from top at 30mph to achieve any kind of appreciable acceleration.
It came with gearing best suited to trail riding. but as both chain and sprockets were shagged, I took the opportunity to fit a larger engine and smaller back wheel sprocket. This made the bike feel much less revvy in nature but still allowed sufficient acceleration in town to burn off most cars and a surprisingly large number of big bikes.
The SP was undoubtedly aided here by its narrowness and chuckability. The nearest I came to trail riding was to imagine the commuting route as a series of obstacles to be taken by any means possible. The SP was great for kicking around seemingly impossible 90 degree bends made by snarled up traffic. the front wheel could be flipped up on the pavement from an acute angle when necessary and l was even known to rear up on the back wheel and flip the front of the bike over car bonnets [Cool story Bro - 2018 Ed.]
The slightest pressure on the bars would have the front wheel off the ground, and I soon became practised in the art of mono-wheeling impressive distances. It was also OK for shooting down country lanes where its relatively high riding position gave me a good view over the hedges and its low mass made up for the wallowing and pitching induced by its trail orientated suspension and steering geometry.
That same riding position made anything more than a constant 60mph on motorways a right pain, although with the raised gearing a contorted body allowed the plot up to 95mph, about what you'd expect from a 28hp single. The drum brakes were just about adequate for town use, although more than one emergency stop a day was probably pushing things. A couple of times I had to lay the bike down and step off rather than risk doing expensive damage to the front end of the bike or, worse still, myself.
The SP is a tough machine and is easily kicked straight after quite heavy spills. Beyond 50mph the brakes are a joke. even with new and harder linings and shoes fitted, fade and lack of power making fast riding potentially suicidal. I had to throw the bike around cars quite a few times to avoid injury to myself and machine; luckily, the SP can be manoeuvred every which way even with the brakes bunged full on!
I also found the bike remarkably economical. Even pissing about in town like a juvenile delinquent returned 75 to 80mpg, whilst sensible riding got it nearer 90mpg. Oil consumption between 1000 mile changes was so negligible that I gave up checking. I use the cheapest trail tyres I can get hold of, they squirm and slide about a bit, but last 25000 and 20000 miles front and rear. A decent bit of chain goes for 9000 miles whilst the sprockets are still the initial replacements.
After acquiring the bike I spent a couple of weekends cleaning off all the muck, painting up the frame and cycle parts and filling in the larger dents. I was later able to buy an SP400 in nice condition save that the owner had seized the motor, so the 370 ended up with a good set of clothes and I had many useable parts.
The motor ran well until 31000 miles when, as predicted by the UMG, the kickstart mechanism failed. It failed hastily too, making an awful row when the engine was running, so required immediate attention. Fortunately. I was able to bodge a repair with the SP400 bits without actually splitting the crankcases. That repair has lasted well with 56000 miles now on the clock.
Other engine problems - it needed a rebore at 42000 miles, although the cylinder head has been fine, probably down to my paranoid oil changes: it went through pattern contact breakers every 800 miles until I stomped up for a genuine set, and it took two new cylinder head gaskets to stop it blowing out oil. Otherwise, it's been a very reliable device. only recently has the gearbox lost a little of its precision (it's still better than some new Honda boxes) and it still goes as fast (or as slow it you're into hyperbikes) as ever. Impressive!
Perhaps because it puts out so little juice. the 6V electrical system has shown none of the normal Suzuki tendencies towards pyrotechnics. The front light is a laugh or disaster depending on whether you're sitting on the bike or running out of tarmac. Indicators were dumped when they failed, whilst front and rear bulbs blow every 5000 miles or so. Luckily, the SP's not my only machine and I can cruise long distances on my big Honda, but the few times I've been caught far away from home in the dark have resulted in a most frustrating, dangerous and slow ride home. Were it my only machine it would have been fitted with a 12V conversion a long time ago.
Cycle parts have been resprayed a couple of times, it now sports a deep British racing green with the odd touch of silver. The suspension is still original, the twin shocks don't have any damping left but it does not produce too many worries in the type of commuting and back road use I make of the SP. The front mudguard was replaced by one that hugs the front wheel and the silencer is a loud universal megaphone, but other than that it's still pretty original.
I let a mate have a go on the SP the other day. He came back white faced and shaking, muttering something about it wobbling all over the road and vibrating like a pile-driver. I've had it for so long that none of these minor idiosyncrasies bother me in the slightest, it still lets me charge through the commuting hordes like a madman and the only thing that I can think of that is cheaper to run is a bicycle!
George Hutchings