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Helping keep British Motorcycles on the road for over 30 years - established 1977

Morgo MK III Big Bore Kits!
Now On Hand!

Over 30 Years Continuous Production!

Outstanding in Design and Performance the Morgo conversion is made to fit any 650c.c Triumph Unit or Pre Unit motor (9 stud head to be used on the latter) without any alterations to any of the standard parts. No reduction in bolt size or separate liners are employed in this conversion. The cylinder barrel is made from high quality cast iron, cast exclusively for Morgo. The casting is one piece and only weighs a few ounces more than the standard barrel.

Supplied with cycle threads as original. Fin area increased by 20% to give greater cooling efficiency. We have introduced a fin tower at each side of the barrel to eliminate fin ringing at high speeds and to give more rigidity. Also the fins are much larger to give added cooling and blend in with the shape of the cylinder head. Most important of all the strengthening pillars go up through the fins to give maximum strength to the base of the barrel.

Thread depth lowered by one full fin section to make available the possibility of removing top fin etc., for special purpose building without loss of thread depth, i.e., short stroke motors.

The pistons are manufactured by one of the world's largest piston producers. All pistons have cutaways for larger valves.

Standard compression ratio is 9.5 to 1 with a standard gasket. Alternative gaskets are available to give compression ratios of 8.5 to 1 and 10.5 to 1.

The standard range of pistons give the following capacities:-

STD 2.975in. = 740c.c. 45 c/ins.
PLUS .020in. = 750c.c 45 c/ins.
PLUS .040in. = 760c.c. 46.4 c/ins.

Care should be taken when using Thruxton Cams on valve to piston clearances.

Now after over thirty years production and continuous research this product is used by thousands of discerning enthusiasts throughout the world.

All kits are now supplied with the Morgo Super Ring Pack.

All Morgo components are made from the best materials to give long and trouble free service.


MORE POWER 750cc. No loss in R.P.M.
MORE STRENGTH All one piece
MORE ATTRACTIVE Design blended to head
MORE SILENT Made from cast iron
MORE RELIABILITY Good engineering techniques used
MORE ECONOMY Improved power to weight ratio
MORE EASY TO START Moderate compression ratio

MORGO the 207.9 m.p.h. name.

Our own test machine, which is a 1963 unit 650 Bonneville, reached a speed of 127 m.p.h. at just over 7,000 r.p.m.

The Conversion comprises of:-

1 Morgo cylinder barrel
2 Standard pistons complete with rings, pins & c/clips.
1 Standard cylinder head gasket. (9.5 to 1)


The success of this conversion depends to a large extent on your assessment of the condition of the rest of the engine, obviously worn parts deter performance and may collapse under added power. The variation in the balance factor on fitting this conversion is negligible.

Note: When placing your order you may wish to add a top end gasket kit, new tappet guide blocks (if yours are worn) as well as an installation tool, ring compressors and possibly cylinder base nuts.

Please note that all parts for these kits are also stocked separately by BCS, including piston assemblies and ring sets in Std, .020, .040, and .060" oversize.

Pistons and rings are now being made by a new manufacturer as of May 2005, and prices and quality have been dramatically improved.

Fitting Instructions (pdf)

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