The Albin 500 motor has a bore and stroke of 79mm x 100mm. The original design goes back to 1942 when Monark supplied a limited amount of these to the Swedish military. The original design is very similar the British Archer from 1936. This motor is the 3rd of a total of 6 Albin motors produced at the Varberg Monark factory. The very slim design and long stroke made this motor ideal for motocross in the late 50's and early 60's. With a 10:1 compression ratio, the motor required 100+ octane and was virtually bulletproof.  Everything from the sand cast cases to the internal parts are hand made.

   The Monark cylinder was the only one at the time to use a chrome bore. Sten had several cylinders and would take them to Karl Schmitz in Germany to be re-plated. Special pistons produced in Germany were used exclusively. The head received extensive modification in regard to compression, valves and port work. The initial set-up, was produced by the Monark engineers at the factory. Sten put in countless test laps at the Varberg track in the winter and throughout the summer to arrive at the initial settings and he continued to try and improve the bike even while he was living in Europe. You can see the head stays that were made to reduce vibration. Before this modification, Sten's hands were completely numb after one race (read Sten's comments on page one). Intake and exhaust valve adjustment could be done externally and there is an inspection cover on the top of the head with a breather tube attached.

                                                  Large aluminum plates hold the crankcases and gearbox to the frame.

   The air filter box and oil tank are hand formed out of aluminum with the oil tank holding over two quarts of Castrol 40 wt. At the top of the air filter case you can see where the clutch cable goes through to keep it tucked out of the way. On the right side of the cylinder head, the oil is fed to lube the top end.

   Oil is circulated to the top and lower end of the motor by an oil pump driven off of the crankshaft. Above are the supply and return oil lines to the oil tank.

    Sten used Lucas and BTH racing magnetos exclusively while preferring the BTH as shown here. On the lower photo, you can see the safety wire on the back of the magneto that has been there for over forty years!

    Spark from the magneto is driven by this chain off of the crankshaft. The whole set-up is very slim and compact. Note the big push rod tubes on the cylinder.

   After testing the Amal GP 5 and TT 9 carburetors, Sten settled on the smaller and more reliable Amal monobloc. This provided more power to the ground and was much easier to tune. With the Grand-Prix's being in many different countries with many different elevations and climates, this was the better choice.

   With the seat removed you can see that the combination of the aluminum side panels, air filter case and rear fender provided a very nice large volume still air-box. Very simple and very effective.

   The BSA gearbox was swapped out in favor of an AMC unit. Four gears with the shift pattern being one up and three down. And as with most bikes of this era it shifted on the right.

   Inside the primary cover is a primary chain that connects the gearbox to the crankshaft. The chain is lubed by a drip system that is fed by the engine breather tube. The Monark engine also uses a dry clutch

                                                                        Beauty and function, all at the same time.

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