Bernard's 175 Page

Experience from over 50 years of KR175 ownership


A Review of Sachs Engines --- Part 1

H
aving run my KR175 for 28 years now and covered some 176,000 miles in that time I felt that I may have something of interest to say to any other 175 owner in the MEC so I offered to write a 175 column for Take Off, to which the editor readily agreed — he also assures me that I am not the only 175 owner in the MEC. However, as I have little spare time I can't promise a column for every issue, we will just have to wait and see how things work out.

A question I frequently get asked is "what do you do for spares?“, to which there is no simple answer. Some items are common to all versions of Messerschmitt, while others are standard spares (such as most bearings) and yet others are spares for some other machine which can be used, maybe after modification. And if all else fails, it is a case of Do-It-Yourself. It would therefore seem a good idea to start by reviewing the evolution of the Messerschmitt, as the various marks have much in common and with the heart of our pride and joy the engine, I will take that first.

Hy knowledge of the engine's history is mainly based on the study of a number of Sachs manuals and illustrated parts lists, plus what I have found when looking inside mine during maintenance.

The story of our engine probably started with the Sachs 150 (146cc to be precise). This had a stroke of 58mm (as did all following models) and a bore of 57mm. The engine was of the counter flow scavenging type so had a deflector piston. The transfer ports were 90° to either side of the exhaust port (looking down the barrel if the exhaust port is at 12 o'clock then the transfer ports will be at 9 and 3 o'clock respectively) and the deflectors took the form of cut-outs on either side of the piston crown, adjacent to the transfer ports.

From engine number 1378157 on there were some minor changes in the design of the cylinder, cylinder head, crankshaft, ignition system and the ratio of second gear. But the essentials remained the same as for the earlier engine and three features to note are; the clutch which had three cork insert friction plates, the crankshaft main bearings that were caged ball races, and that the piston only had two rings.

The 150 seems to have started life as a motorcycle engine, which was then adapted for use in scooters and microcars. As a result there were a number of options, including; ignition ranging from flywheel magneto to coil and battery and electrics from a flywheel lighting coil to the flywheel dynamo (with electric starter and no kick start). Variations in cooling were also available, from simple airflow to fan cooling — which incidentally required an alternative head with the cooling fins near enough at right angles to those of the original head.

The next development was the 175 (173cc), with the only real difference from the later 150s being an increase in the bore to 62mm and a small increase in power output. All the extras for the 150 were also available for the 175. Then sometime before 1955 the crankshaft main bearings were changed to caged rollers and the three clutch friction plates to the composition type fitted to the later models.

There were now also two different sets of gear ratios — fitted according to use, one for motorcycles and scooters and the other for microcars. Here the parts list is interesting as it quotes the latter gear ratio set as for "Messerschmitt-Roller und Fuldamobil". Has anybody heard of a microcar called a Fuldamobil?

The Sachs 175 also saw the introduction of an add-on mechanical reverse which the owners manual suggests was standard in the KR175. But I have seen KR175s with the non-reversing engine — probably a UK option, available to satisfy the driving licence requirements of the time.

Then in 1955 the Sachs 175 model 55 made its appearance, but that will have to wait until next time. Meanwhile, if any reader has additional information or wishes to take issue with anything I have said then I am sure the editor would welcome your letters.

#1 from Take Off Volume 11, April 1988