The Kay MV Agusta engine - Great Engines in Bits

great engines in bits

An article by Mick Duckworth for Classic Bike Sep 2013.   Photos by Dave Collister and Simon Hipperson


MV combustion chambers


Shallow Combustion Chambers: The cylinder head shows a marked step forward in power generation compared to earlier MV engines. Four-valve heads with with central spark plugs were by no means novel but Honda had shown how they could significantly boost efficiency - especially with narrowed angles between the inlet and exhaust. The resulting shallow combustion chamber promotes the rapid combustion of fuel

A Review of the Kay MV 500 GP

Engine Construction


The engine shown here is not a 1960s’ survivor but a faithful replica created for historic racing by skilled engineer Mark Kay. He and his father Dave have been a dynamic force in the MV Agusta world for decades. Several years ago they resolved to replicate a small number of Agostini triples, with help from their trusted suppliers, mainly UK-based. This is their own Black Eagle Team’s 500cc engine.

The crankcase is in one piece and cast in light magnesium alloy as are the engine’s various outer covers. The longest part of the casting, is only 540mm (21in) from front to back. A one-piece cylinder barrel also forms the upper crank chamber and is fixed by 14 studs to the crankcase opening, where an angled joint gives the cylinders their forward tilt. The crankshaft is fixed directly to the underside of the barrel by four alloy main bearing carriers on studs. The outer two carriers are one-piece blocks with caged rollers pressed into them, while the inners are split across the crank’s central axis and contain loose rollers.


Crankpins on the built-up crankshaft are disposed at 120degrees and each one is between a pair of webs shaped like pineapple segments. The elegantly shaped steel con-rods have single wrap-around bands of extra metal to reinforce their big-end eyes, which house caged needle roller bearings.


Looking at he Kay MV Agusta engine - Great Engines in Bits


gifAn array of MV engine parts

An array of MV 500-3 engine parts, laid out in the Kay's workshop


Mick Duckworth reports on the Kay MV Agusta engine - Great Engines in Bits

The gudgeon pins run direct in the rods. The slipper-type pistons have short skirting at the front and rear only, and inset gudgeon pin bosses. The piston crowns have transverse flat-topped raised ridges to suit the combustion chambers, with indents to clear the valve heads.


Primary drive is taken off the crankshaft on the left, where a pinion engages with a much larger gear interlocked with the dry clutch’s basket but separated from it by a cover plate to keep oil in the gear chamber. The crossover-type gearbox has its secondary shaft under the primary shaft carrying the clutch and output sprocket, helping reduce the length of the power unit.


Dry clutches favoured for racing have a much higher co-efficient of friction than the wet type. Rattle is not an issue and being exposed helps disperse heat. This compact design follows a basic pattern used since the 1920s, with five coil springs under adjuster nuts in cups on a pressure plate. While needle roller bearings and a thrust bearing keep the basket spinning freely on the mainshaft, the driven clutch hub is fixed on splines and secured by a nut.

magnesium alloy crankcase

The lightweight magnesium alloy crankcase is a one-piece casting


Mick Duckworth reports on the Kay MV Agusta engine - Great Engines in Bits




This gearbox has six ratios: the triples also raced with five and seven, but FIM rules imposed a maximum of six from 1969. The change drum, here perforated for lightness, is behind the secondary shaft and shifts three forks pivoting on two shafts. It is operated, via a positive stop mechanism, by a pedal on a shaft supported in the box’s right-side end plate. All the internals are held by the plate, so they can be withdrawn as a single assembly in cassette-fashion once the clutch is removed.

In the cylinder head, the valves are not angled symmetrically. The inlets, which are predictably slightly larger than the exhausts, are at a 5-degree steeper angle than their counterparts. Separate valve seats are fitted.

Each camshaft is supported in four bearings and a circlip at one of them ensures zero end-float. . There are ballraces at the drive end, but the other bearing have loose rollers, which must be laboriously inserted in their races using indented scallops on the shaft, since the lobes on the one-piece shafts don’t allow complete races to be slid onto them.

The Kay MV Agusta engine in Bits


Each bearing is held in place by a cap secured by a pair of studs, which fit recesses for them scalloped on the outer races. The cam lobes contact directly with bucket pushers on top of the valve stems that surround paired coil springs.

The six pairs of buckets, perforated for lightness, are in slider blocks above the valve guides. The twin-gear oil pump sits in a recess in the crankcase casting behind the clutch and below the gearbox cluster, turned by a gear engaged with one behind the driven primary gear. Oil is drawn through a pipe from a gauze filter in an assembly fixed in the sump floor. From the gallery, oil is fed directly to the two inner main bearings (the outers are splash-fed).

Oil for the top-end goes up galleries on the right of the block and into the head where drillings lead it into the detachable camshaft end covers, which carry spring-loaded brass feeders to transfer oil into the hollow camshafts.

Drainage back to the sump is via the cam drive chamber. Oil is pumped to the gearbox via a T-shaped alloy union leading it to another spring-loaded feeder pressing on the end of the hollow secondary shaft. Steel baffle plates are slid into channels in the sump to prevent oil surge on acceleration and braking. MV ran magnesium-bodied Dell’ Orto SS1 remote-float carburettors with choke sizes from 29mm to 31mm. The Kays have some new-old-stock SS1s, but also manufacture new replicas.


The Kay MV Agusta engines revealed - Great Engines in Bits

Racing the MV Triple today


MV triple racing


Three 500cc and one 350cc Kay triples to 1972 specification have been raced by Alan Oversby and Gary Johnson on the IoM’s Mountain and Billown circuits, as well as by Phil Sharpe at the Goodwood Revival and at Mettet in Belgium where Brian Richards won a 500cc IHRO race in 2010.


TT Course success has been elusive: sure wins were lost by a rear brake linkage failure and hitting a flock of starlings.. “We will win,” says Mark. Oversby’s best lap at 109mph in the 2010 Classic Manx GP, bettering Ago’s 1967 speed, was an important milestone for the Kays. In that year Oversby took a Junior Classic third place on the 350.


Under the Black Eagle Racing Team banner since 2008, the machines carry Kay logos to comply with a trademark ruling. However, the Kays have been granted the web address and trade as Meccanica Verghera Ltd. Giacomo Agostini himself has taken a spin on a Kay triple which met with his approval. “Our engines are kept close to the original specification, which we’ve found most reliable,” Mark Kay says. “Maintenance is labour-intensive. Crankshafts are good for 300 miles of racing but will go much further if only paraded. Although the 500 can rev to 12,500rpm, we only go to 11,000rpm for safety. “Assembling the crankshaft and pistons into the cylinder block is a major operation that can take hours – it’s not a paddock job. But I like being able to lift the head without disturbing the timing and the Vernier camshaft adjusters are brilliant.” The Kays are now busy replicating the later four-cylinder GP engine.


gear driven cams

Gear driven cams


1970 Kay MV Agusta replica Specifications


Type: air-cooled dohc in-line triple

Capacity: 497cc

Bore x stroke: 62.5 x 54mm

Compression ratio: 12.5 :1

Carburation: 3 x 30mm Dell’ Orto SS1

Ignition: electronic (originally cb points and coil)

Firing order: 1-2-3

Spark advance: 42 degrees BTDC

Valves sizes: inlet 24mm, exhaust 22mm

Valve timing: inlet opens 50 deg BTDC, closes 74 deg ABDC,

exhaust opens 75 deg BBDC, closes 54 deg ATDC

Valve clearances: 0.17mm inlet, 0.22mm exhaust

Lubrication: wet sump, twin rotor pump

Primary drive: gears

Oil capacity: 3 litres

Clutch: dry, multi-plate

Gearbox: six-speed

Output sprocket: 19 teeth (IoM gearing)

Final drive: chain

Power output: 75bhp @ 11,000rpm (at rear wheel)

Weight: 260lb

The Kay MV Agusta engine - Great Engines in Bits

Here we look at Kay MV Agusta engines - Great Engines in Bits