Contact Breakers – updated 2020

Messerschmitt (SACHS), engines were fitted with two different types of contact breakers. One type is SIBA fitted to all engines up to 1958 and fitted with SIBA starter system. The later type BOSCH equipped engines had a different contact breaker system. Both types are interchangeable by using the appropriate contact breaker mounting plate.

MOC offers new back plates to suit SIBA contact breakers. These come complete with a new felt pad that should be lubricated with BOSCH grease, (available from Partsmart), to prolong the life of the Crankshaft cam and the contact breaker heel. BOSCH contacts have been unavailable as proprietary items for more than 20 years.

When setting the contact breakers, note that the time/position that the contact breakers open is the most critical part of the setting. The single lift cam has adequate time for re-charging the coil voltage at almost any gap setting. It is often not possible, (due to a worn cam), to set the gap to the correct specification together with the correct opening point. In this case, set gap as near as possible to the specification with the opening point at 4.5mm to 5.5mm before TDC. For the reverse timing, the gap is always a compromise, and adjusting the gap is the only way to achieve the correct opening point of 3mm to 4mm before TDC. The reason for this is that many cams are seriously worn from previous neglect of the felt pad and failure to use BOSCH grease. See articles in the Partsmart publication, “Karo-Tips”.

The following is a summary of the various contact breaker types, together with cost and fitting details:-

Siba

Contact breakers originally fitted including a retaining clip for holding the coil wire as it passes through the clutch housing. Forward direction is marked ‘V’ (German – Vorn = forward). These are interchangeable with the reverse assembly marked ‘R’ (German – Rueckwarts=reverse). The R or V is upside down if the two types are transposed. This does not affect operation. The Black wire connects to ‘V’ on the right-hand set of contacts. The Red wire connects to ‘R’ on the left-hand set of contacts.

Part No. 279: Original Schier Kontakte part no:4681, Marked ‘V’ (forward) but may also be used in the reverse position. No longer available.

Replacement back plate for SIBA contact breakers, complete with new felt pad. Accepts original contacts above or the cheaper Villiers engine type listed below.

Part No 280 Siba backplate – Available from Partsmart

Bosch

Contact breakers originally fitted including a retaining clip for holding the coil wire as it passes through the clutch housing. Forward direction is marked ‘V’. These are not interchangeable between forward and reverse. Reverse direction is marked ‘R’. New BOSCH mounting plates are not available. If your contact breakers are worn out, you should convert to SIBA type with a new backplate.

Part No 278 Original Schier Kontakte part no:2162, Bosch part no: ZKT 72Z4Z forwards. No Longer available

Part No 281Original Schier Kontakte part no: 2163, Bosch part no: ZKT 72Z5Z reverse. No Longer available

ALTERNATIVE, NON ORIGINAL PARTS:- SIBA

Contact breaker assembly as used in British Villiers engine. These are interchangeable with the reverse assembly. The forward assembly is fitted with a black cable and the reverse is fitted with a red cable. To fit these to a SACHS engine it is necessary to shorten the cable and connect to the appropriate wire using an insulated connector block, (not supplied). There is ample space within the contact breaker cover to fit the connectors. These contact breakers can be used with the above SIBA backplate, (Pt. No 280), to convert a BOSCH contact system to SIBA.

Part No 277 SIBA contact breaker assembly, (Villiers Type), state forward or reverse, available from MOC.

Ignition unit – inductive discharge – retains existing contact breakers

Worn contact breakers can be used almost indefinitely by using these systems as the contacts become a simple switch with no significant power flowing.  See: Link to external site

ELECTRONIC IGNITION SYSTEMS

There were 3 suppliers in Germany for electronic ignition systems for KR200; Steini-KTZ, Pukes, and a third one with programmable advance features. The systems are fully integrated into the existing contact breaker housing and an impulse rotor is attached to the crankshaft. The two existing wires and the engine ground are used as control and supply for the unit. Reversing system operates as before as the impulse sensor is timed exactly for the opposite direction of rotation. This is not a cheap solution but the spark is improved with more reliable running. A significant advantage is the easy replacement of the original contacts in case of failure on the road. For a compact unit that fits in the contact breaker housing.  See  Link to external site