MV Meccanica Verghera Ltd repairs and restores MV Agusta and Gilera motorbikes

The Kay Three Wheeler



(Extract from MV Agusta Fours - The Complete Story by Mick Walker)


At the centre of controversy from the moment it was unveiled in 1985, the Kay MV 4-cylinder racing sidecar was a neat piece of kit. Maybe it was too good, getting its opponents up in arms before the flag had dropped.


Dave Kay, a founder member of the MV Agusta Owners' Club in the early 80s, was also a highly skilled engineer and a sidecar racer of some repute. His career on three wheels began as a passenger to friend and fellow MV enthusiast Bill Johnson. At first the pair campaigned a very quick Laverda Jota-powered outfit at club meetings during the late 1970s, and then Kay became a driver at the CRMC (Classic Racing Motorcycle Club) events during the early 1980s with an immaculate 1200 NSU. This involvement with sidecars, coupled with a lifelong love affair with MV Agustas, was bound to coincide sooner or later. For years, he had discussed putting an MV four engine in an outfit for classic racing, and by the middle of the 1980s he had done it.


The result was a superbly engineered machine that was a credit not only to Dave Kay, but also to Ron Graham, his friend and business associate, who had contributed both money and expertise to the project.


The Kay outfit consisted of a 1972 750 Sport engine, housed in a chassis purpose built by John Derbyshire. The design was such that the power unit, which was held in place by 7 mounting bolts, could be completely stripped from the chassis in under ten minutes - easy access being all-important in a racing machine.



If only the top section of the engine needed attention, the cylinder head and barrels could be removed with the engine in situ. The nearest frame tubes were removable for access to the clutch and for sprocket changing (a Magni chain drive was part of the specification) on the crossover shaft.


The massive box-section swinging arm was controlled by a single Dutch Koni shock absorber. This was mounted on eccentris bushes, which enabled the drive chain to be adjusted in less than a minute. Car-type cast-allow wheels were used, running on 145x10 Dunlop Green Spot tyres. Braking was by Lockheed. The system worked with the handlebar lever operating one of the twin front discs, while the foot-operated brake pedal operated two master cylinders - the first the other front disc, and the second to work the rear wheel and sidecar wheel discs. There were four discs in all, with twin-piston calipers on each. All wheels were quickly detachable, leaving the calipers and discs in position.

The sidecar engine


Modified frame to meet CRMC new rules

The sidecar engine

The 750 Sport engine was largely of standard specification, but blueprinted to achieve the best possible power output, while retaining a high level of reliability. Several road-going components had, however, been removed, most notably the Dynostart, which alone saved 20lb (9kg). Although the standard five-speed gearbox was retained, a chain final-drive conversion by Arturo Magni, one time MV racing team manager, had been fitted. Not only did this absorb less power than the original shaft arrangement, but, perhaps more importantly, it also allowed the gearing to be altered quickly for circuit conditions.

In view of the extra stress expected, an additional support bearing had been machined into the outside spyder outrigger to give extra support to the fifth gear on the mainshaft. A higher-lift camshaft profile was employed which, together with an increase in compression ratio from 9.5:1 to 10:1 and modified inlet tracts to suit the 30mm Dell'Orto PHF pumper carbs, pushed maximum power to 90 bhp.


The effective range of power spanned 5 000 to 10 000 rpm. The special one-off four-pipe exhaust system was the work of Midlands engineer Dave Kerby, to Dave Kay's own specification Ignition was by coil and battery via a car-type distributor (ex-Fiat). The battery was housed at the front of the chair under the perspex bubble, with the fuel pump under the rear of the sidecar platform, hidden away neatly behind a skirt together with the fuel filter and pressure regulator.

The MV engine is peculiar because the final drive is close to the centreline of the motor. To achieve a proper relationship between front and rear wheel it was necessary to fit a crossover shaft to drive the rear wheel on the nearside - standard sidecar practice on Imp-powered specials. The shaft used was a Z400 Kawasaki mainshaft on which were specially made sprockets. The centres of these sprockets were cut by Ron Graham using a Spark Eroder. Although cutting with one of these is fully automatic it took five hours to make up the required tool; as each electrode is only good for cutting six sprockets. Ron missed out on some drinking time for a week or so! As both crossover shaft and engine mainshaft are of fixed centres, it was necessary to install an eccentrically mounted nylon jockey pulley to take up slack in the external primary drive chain.

Originally fitted with a 1960 DMD dustbin roadster fairing (but suitably modified with airscoops and quickly detachable mountings), the Kay MV racing sidecar outfit was fitted with a small handlebar fairing.

An aluminium fulel tank was hidden from view beneath the sidecar wheel arch; three holes in the wheel fairing were to direct cool air to the sidecar wheel disc.

Following some forty laps of the Cadwell Park club circuit at a practice day, the Kay MV was entered for a Retford Club meeting at the same venue. Although competing against modern machinery, the bike was not disgraced, despite a fourteen year old engine and a chassis constructed to an out-of-date design built specifically with classic racing in mind. However, this was where the problems started. Soon after completion, the Kay outfit was banned from CRMC classic racing events, after wrangles over its eligibility.


Click here to read about a famous race.


The sidecar frame


The Black Eagle Racing Team rode MV Agusta motorcycles at Donington