Simson 425S 1961 
A Full Sized Lightweight
SIMSON produced 250 cc overhead-valve shaft-driven singles derived from pre-war BMW design, which were originally known AWO. From 1 May 1952, the company became a VEB (nationally owned plant) although the bikes still wore the AWO name on their petrol tanks. In 1957, the old SIMSON name was resurrected, as exports were urgently needed and, in exhange for oil, many AWOs were delivered to Romania.
The output of the company rose to annual total of 20000 machines but, despite changes to various like the forks, brakes, shaft and exhaust, a little 250 was alredy looking its age by 1954. The same year, the gearbox was modified for better and easier use an attempt to counteract heavy wear caused by the gearshft rotating at crankshaft speed. A new layshaft helped a bit, but qiuet cog-swapping could still only be obtained by experienced riders.
Something more modern was presented to the public at Christmas 1955, the AWO 425 S, or Sport AWO. With is launch, Simson had a modern, op-to-date motorcycle on offer. An all new frame was complemented by a revised set of forks and swinging arm rear suspension, all of which made for a comfortable ride. Wheel size was reduced to 18 in and tank meant 16 litres of fuel on tap, the revised engine offered 14 hp thanks to a compression ratio of 7,2:1 and a new 25mm carburettor. Rockers ran needle-roller bearings and the inlet port was bigger and less angled.
The new machine did display some niggles. Vibration not only destroyed bulbs, speedos and loosened nuts, it could slowly, but steadily, reduce the frame to scrap. Also shocks and fork legs were not leak-free in the first few procuction years of the S-type, though Simson was able to cure this problem fairly quickly.
In 1960, the 425S was slightly modified. A new head gave a compression ratio of 8:1 and 15,5 hp at 6800 rpm. The engine was finally rubber mounted reducing vibes to a minimum. Unfortunately, it was not to last for long. In December 1961 the GDR government decided a 250cc four stroke was an unnecessary luxury for the people of the GDR, and from 1962 only two-stroke mopeds and scooters left the Simson factory at Suhl. Simson also produced successful 250cc capacity road-racing competition models, see Photo Gallery.
Restoration
My 1990 restored Simson 425S introduced in 1961, frame and engine number 225134, was the final development of shaft driven Simson.
As time passes, so authentic and unrestored machines, in the condition they left the factory, become harder to find. To find a machine that is completely original, has stayed in the same area all its life and has only had one owner from new, is always welcome when looking for a restoration project. When that machine has been used on the road for less than two years (3200km), there is even more cause to celebrate. Internally, both engine and gearbox required nothing in the way of new parts. Bearings were replaced throughout, but only as a precaution. The original crank was in sounding condition, as was the clutch and schaft final drive, and even the cylinder head was in perfect condition.
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The Simson 425 S tried hard to give its rider a "big machine" feel.
Long, tall and single. Schaft final drive is synonymus with the Simson name. Cast alloy front drum brake provides ample stopping power. Simson engine is an indisputably attractive unit. Unlike some continental machines of the early post-war years, the Simson was fitted with a real tank badge, underlining the quality build of the machine.
The Simson was fitted with either a single BVF carburettor. BVF carburettor give phenomenal economy. Easily capable of 3,5 l/100km, the Simson is as economical as many less lively machines. The instrument layout is simple and yet functional. Just what you´d expect from a sixties motorcycle. From any angle this motorcycle seems to be inviting you aboard for the ride.
Overhead valve engine is a typically clean unit construction desig. Handsome and beautifully finished engine has enough urge to take the little Simson up to 110 km/h and will happily maintain 90 km/h cruising speeds.
Not the fastest thing on the road by any manner of means, but the Simson provides a pleasant ride with safe and predictable handling. Even the manufacturer's toolkit was still with the machine when I bought it.
How much has all this restoration work cost? The complete engine, all new bearings, seals and balance the crankshaft came to a total 100€. Chrome plating, with the new stainless spokes coming 400€. Paint cost 100€, with all the other less expensive parts, the total cost 1000€.
How does it run? On the road the Simson proved a gem. Acceleration is brisk and the engine runs through the rev range with a minimum of mecanical noise. The exhaust note is that of a busy sporting single, enough to turn discerning heads but not so loud as cause offence. The manual lists 120 km/h as top speed even though it has a 120 km/h speedo. The Simson 425S was not offered in a hot version. Nevertheless, the Simson has good torgue and four speeds in transmission make it nice to ride. The shaft final drive is clean, easy to maintain and didn't spoil the looks of the machine with oil splashes, or suffer the bugbear of chain and sprocket wear. It hums along at 90 km/h just fine. It is light and when astride of it feel more like you are on about 500 cc bike. It does handle well, however, and the vibration is not bad for a single. It´s quick enough for me and my wife and it can be great fun to embarass riders on more modern machinery.
A Sixties 250cc ohv lightweight is not everyone's idea of the perfect motorcycle, yet they make a good compromise. They are ideal for local trips and longer hauls too. I use my Simson for both. What they lack in size they make up with style and finish.
But is the SIMSON a classic motorcycle? People's reasons for judging a bike a classic is mainly emotional. They see a bike and say yeah, that's a classic. What about if it is not technically innovative, if it never won a race, if it sold a lot? You can apply logic. Like with the Simson 425S. You can apply logic and judge it a classic.
For me, this Simson is as pretty as a picture, and represents all that is good in classic motorcycling.
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DREAM TIME
Classic motorcycles don't have to be big, fast or expensive to be fun.
Simson and Summer go together, so where better to enjoy the classic motorcycles than
riding across Lapland at the midnight sun. You can't ride it anywhere without it
turning heads. People think it's amazing.
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1. June 2002 at home in Vojakkala I and my wife Terttu
with Frank and Barbara from Potsdam.
2. Ready for the road. Terttu with Frank and Barbara.
E-Mail: nasser@luukku.com
