Black Box V5.1 Guida alla Risoluzione dei Problemi Scaricare il pdf (Pagina 24)

Euro MotoElectrics, 25958 Genesee Trail Road PMB 321 Golden, Colorado USA 80401 EDL-IGN Page 24 of 43

www.EuroMotoElectrics.com info@euromotoelectrics.com Tel: 1-303-526-0901

EnDuraSpark Electronic Ignition

Installation & Troubleshooting v5.1

Airhead Timing Marks

1970 - 1990 BMW Airheads have three timing marks stamped on the flywheel:

 OT: Top Dead Center used for adjusting valves & EnDuraSpark timing.

 S: Static Ignition timing, Spaetzuendung, minimum or retarded

advance. This is the timing mark to use when timing with the engine off

or at idle.

 F: Fast ignition timing, Fruehzuendung (spark advanced), the

maximum ignition advance. On later engines, the letter “F” was

changed to a “Z”.

The horizontal line above the “S” and the dot above the “F” are the actual marks

to use for timing. Some flywheels have two lines, one above and one below the

timing letter. These indicate the permissible "range" of the timing, +/ 3° due to

“split images”, i.e., the difference in timing between the right and left cylinders.

Turning the engine over, peering into the timing window, the flywheel will

appear to be moving down. From the perspective of a rider sitting on the

motorcycle, the flywheel, crankshaft, rotor, camshaft and timing wheel all turn

counter-clockwise.

When viewing the flywheel with a stroboscopic ignition light, the “S” horizontal

line should appear at idle. As the RPM is increased, the “F” dot mark will slowly

move up from the bottom into the window. It will stop moving up at about 2200

– 3800 RPM, depending upon model.

Rarely there may be a flywheel installed incorrectly on the crankshaft (being some

multiple of 72° off) so all timing marks are in the wrong place. Re-install

the flywheel correctly by installing the flywheel on the crank at TDC (pistons fully

extended) with the "OT" mark in the timing window. Flywheels that have been

lightened and/or balanced may also have had the timing marks machined off the

flywheel. Put them back by measuring the distances from OT to the “S” and “F”

marks from the chart on the next page.

The diameter of all 1970-1980 Airhead flywheels is the same: 736.6 mm. So 1° of crankshaft

rotation corresponds to 2 mm (2.046 mm actually) on the flywheel. The only exception to this is

the R65 flywheel, which is 200 mm smaller in diameter. 1° of rotation of an R65 crank

corresponds to 1.5 mm on the clutch carrier (flywheel).

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Black Box V5.1 Guida alla Risoluzione dei Problemi Pagina 24