Norton Commando Workshop Manual

## Engine/Primary Transmission

# C

9 | Rotate the engine backwards gently until the machined mark on the rotor registers with 28° on the indicator plate. At this precise moment the contact breaker points should start to open in which case timing is correct.
The exact point of separation can be determined by inserting a strip of very thin paper between the points. The points will grip the paper when closed. By moving the engine slowly, a light pull on the paper will dislodge this at the exact point of separation. Take care not to leave a shred of paper between the points when using this method. A preferable method is to use a low wattage bulb and holder with a short length of wire attached to the bulb body with a second length of wire attached to the bulb connection. Crocodile clips should be attached to the loose end of both wires. Connect one wire to the contact breaker spring of the set of points being checked and the second wire to a suitable earth point on the engine. Switch on the ignition and as the engine is turned, the bulb will light at the exact point of separation.
10 | If the timing is incorrect, i.e. the points do not open at 28° before T.D.C., release the two screws in elongated holes which secure the main backplate and rotate it in the housing. To advance the timing, move the baseplate clockwise and to retard, move the baseplate anti-clockwise. When the timing is correct, secure the backplate screws.
11 | Using the same technique, check that the contact breaker points open at 28° B.T.D.C. on the firing stroke for the second cylinder. If incorrect, make adjustment by movement of the secondary backplate. To do so, slacken screws (A) in Fig. C47 and use the eccentric headed adjusting screws (B) to move the mounting plate. When timing is correct, re-secure the screws (A).
Ignition Timing Procedure - Engine Running
(Stroboscope Method)
This method is greatly preferred for extreme accuracy in setting. Prior to checking timing, clean and set both sets of contact breaker points to the figure given in "General Data."

Note that late models have two marks on the rotor but that if the ignition timing is sufficiently correct for the engine to run at all, the stroboscope will only detect the correct marking. If the engine has been rebuilt and ignition timing is being set from scratch, firstly follow the basic procedure in the preceding text. Commence stroboscopic timing as follows:
1 | Remove the inspection cap on the chaincase to reveal the degree indicator plate and timing mark on the rotor.
2 | Connect the stroboscope to the H.T. lead on the right cylinder and use a battery separate to that on the motorcycle to power the lamp, thus eliminating possible incorrect readings. For the full method of connection follow the stroboscope lamp manufacturer's instructions.
3 | Identify by lead colours the set of contact breaker points on which timing is being set by the colour of the wiring at the points and the ignition coil.
4 | Start the engine and run at a steady 3000 r.p.m. indicated on the tachometer.
5 | Shine the stroboscope lamp on the indicator plate. If timing is correct, the rotor marking will register with the 28° marking on the indicator plate. If the marks do not align, the timing must be adjusted.
6 | To adjust the timing at the first set of points, release the two screws in elongated holes which secure the backplate and rotate it in the housing. To advance the timing, move the baseplate clock-wise and to retard, move the baseplate anti-clockwise. Move the backplate on its slots until the rotor mark and 28° marks align when checked with the stroboscope then secure the backplate screws.
7 | Reconnect the stroboscope for the left cylinde and again check for rotor mark alignment at 28°.
8 | If timing is incorrect for the left cylinder, correct by slackening off the clamping screw for the secondary backplate for this set of points then use the eccentric headed adjusting screw to move the secondary backplate (see Fig. C47-secondary backplate screws are marked "A" and eccentric screws are marked "B"). Recheck timing with the stroboscope and when correct, secure the screws "A".

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