Classic Bike Guide - Real rides, real riders

Kawasaki S1 250

Kawasaki had a very competent 250cc machine prior to the launch of the S1 in the shape of the A1 two-stroke twin. Technologically advanced, the A1 ran disc valve induction and a piggy back alternator and ignition system behind the cylinders.

Certainly capable of being developed and upgraded, this very successful twin was dropped in favour of this month’s featured machine.

Kawasaki’s smallest triple ousted the twin for one primary reason; potential sales prospects. If a learner bought into the triples concept there was every chance he’d upgrade to a similar machine when he wanted something bigger. Clever PR and marketing can sow the first seeds of brand loyalty very successfully.

THE BIKE

Arriving in Europe a little after the larger S2 350cc model, the 250cc S1 hit the ground running in early to mid 1972. With those sweeping triple-line graphics and tail-piece, the machine made a bold styling statement that others would only have the courage to emulate years later. Sharing a significant number of parts with the larger S2, the smaller model was distinguished by its six-finned cylinders rather than the seven found on the 350.

This donated architecture effectively hampered the smaller triple to a degree as, to all intents and purposes, the bike was largely a 250 pulling around a 350 body.

However, at the time this was common practice as demonstrated by Honda’s K250 and 350 offerings and Yamaha’s YDS7/YR5 or their later RD250/350 offerings. For 1973 the S1A replaced the S1; largely borrowing the upgrades and changes of the 350cc S2A, except for the front brake, which remained as a TLS drum. The most obvious differences were the change of colour schemes and graphics. Likewise in 1974, the S1B taking its lead from the bigger bore 400cc S3.

Although still every inch a Kawasaki, some feel the aesthetic changes somehow muted or sanitised the smallest triple’s visual appeal. The following year (1975) saw a similar scenario for the S1C, before the arrival of the KH250 that finally came with a long needed front disc brake. Unfortunately with an eye to burgeoning legislation and emissions the entire triple range (and every other performance two-stroke of the generation for that matter) began to lose its marketing appeal, gradually turning from leading light to social pariah.

All of this muted its unique appeal, initially in the US and gradually by default in Europe. For many the first model is the definitive 250 triple to own, yet anyone who is fortunate enough to have the opportunity to experience any of the S1 range is unlikely to be disappointed.

Part of the unique appeal of Kawasaki triple ownership has always been the auditory delights of the bike. The exhaust note is like nothing else, add in the typically poorly silenced induction roar and 1970s heaven is never too far away. The middle pot of a triple will always run hotter than its two partners and internal clearances were allegedly always massaged to take this into account. There are all manner of rumours, urban myths or tales about the middle pot of a triple and airflow; whatever the truths or otherwise it all adds to the legend and aura.

The handling of the S1 is pretty much on a par with its contemporaries such as Suzuki’s T250 or Yamaha’s DS7 but not as crisp as the later RDs. Even now the motor of a properly set up S1 cannot fail to impress with its ultra smooth running. A three-cylinder two-stroke has all the correct and self cancelling rocking couples and harmonics. One indisputable fact is the original TLS front brake suffers from fade after a few heavy applications. That brake struggles to get below a 36 foot breaking distance from 30mph. Six foot may not sound much until you realise 30 feet was pretty much the accepted norm; another 20% stopping distance could make a huge impact (sic).

Whatever the nit-picking differences there are intangibles that come free with every 250 triple. No other 250 has three pots, an asymmetric exhaust tail plane or that unique sound. The way the early tank graphics are continued from the tank through to the tail piece were pretty much a Big K invention and this early graphics package  effectively cemented a standard that has been carried on in general terms to the present day. A definitely unwelcome, detractory, fact of life with S1 ownership has to be the fuel consumption; they are all cursed with a dipsomaniacal thirst.

Spirited riding can see go juice disappearing through the motor and out into environment at a frightening rate; figures as low as 20mpg have been reliably recorded. The 250cc triple is a product of its time, designed and constructed when petrol was less than 35p a gallon and frugality was never in the game plan. By the time this S1C was launched various political, environmental and energy crises’ meant fuel was no longer such an inconsequential consideration as it might have been a few years earlier in a teenager’s criteria.

However, sales figures suggest many decided the baby triple’s unique high street image still outweighed costs and penalties. No doubt the banshee wail of the quarter litre triple and  trefoil plume of partially incinerated hydrocarbons, escaping wraith-like from the carbon encrusted baffles, made up for any fiscal frailties. 

FAULTS AND FOIBLES

It’s a performance stroker so rings, piston and little ends will have experienced a frenetic life so make sure the engine’s not on maximum oversize; re-sleeving will cost around £100 a pot. Outer crank seals can leak, so look for an oil leak on the left-hand side near the points, or gearbox oil being dragged into the engine from the right-hand side as evidenced by excess exhaust smoke out of the same exhaust. The middle pot can seize and big ends can rumble, which is bad news. Some bikes suffered with jammed cranks; the lead weights pressed into the flywheels sometimes fretted their way loose locking the motor solid; often on standing. Repair is straightforward but requires the cases to be split and the crank lifted out.

Second gear can fail due to bent selector forks. The pins on the gear linkages can wear, allowing the lever to touch the rider’s foot and this unintentional connection can place further strain on the system. Look out for pitted fork legs and leaking seals. Rear shocks were never good even when new so quality aftermarket units are not necessarily a bad thing. Tin ware, air boxes, rear tail units etc., can be difficult to source so buy as complete a bike as possible. The original TLS drum was never ever so good so don’t expect wonders. Modern friction materials matched to perfectly round drums will make the best of what’s available along with careful setting up of the front unit. The electrical department was standard Japanese fare of the period; good enough when new but undoubtedly tired now. Corrosion and oxidation allied to meddlesome owners are likely to be the biggest issues.

COSTS AND OPTIONS

Anyone who runs and rides, or restores, the first S1 model deserves a medal without doubt. These iconic machines must be some of the most difficult triples to restore or keep close to original. The correct parts are hard to obtain and the finish on the S1 engine cases is pretty much unique.

The later S1C is, realistically, a slightly more practical option from a restoration or running and riding perspective. However, to be brutally frank and objective, the subsequent KH250 is easier to obtain fettle and maintain. All of which obviously adds to the cachet of S1 ownership. Ultimately Kawasaki S series ownership is more about buying into a marketing and image concept rather than owning the definitive 250cc performance machine. The ultimate two-stroke triple performance accolade was there to be had but not at learner level. Who cares? For a 1970s teenager form normally took precedence over function and the visual statement made by the S1 remains, without doubt, light years beyond any of its contemporaries.

The values (even in a recession) suggests that a first off S1 in pretty much top notch trim will run to £3.5-4K; likewise for the super rare S1A. Any other S1 is likely to run at £800-£1500 for an average machine with £3-3.5K for perfect examples. None of the above is for peanuts but sometimes you simply have to pay to be part of the scene.

Words by Steve Cooper  Photographs from Mortons Archive.