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Your Commando should have the 10 CA contact breaker assembly,a circular base plate with independent contact sets mounted on it,elongated slots in the base plate allow equal movement of BOTH contact sets,either adavance or retard timing on both cylinders by an equal amount.
To set timing from scratch -- remove spark plugs,adjust the gap on both sets of contacts -- the contact set should be mounted on the tapered camshaft nose,a small mark located near the lubrication slot on the ignition cam indicates the highest lift point,rotate the engine until the mark aligns exactly with the nylon heel of the contact breaker,at this position the points are fully open,the gap should be .015",if the gap is something other than .015" you will need to slacken the contact breaker fixing screw -- the one that attaches the contact to the base plate -- the gap is altered by using a small screwdriver to move the contact plate to obtain .015" gap.
Now for timing -- remove the centre bolt from the auto advance unit,a special washer is required for the following procedure -- any washer that will clear the bolt diameter and tighten against the face of the ignition cam will work -- place the washer on the bolt, turn the auto advance unit to full advance position and tighten the bolt to hold the AAU in position -- the AAU will only rotate one way --CCW I think.
Timing the LEFT side cylinder,rotate the engine until piston is at TDC and both valves closed,the yellow / black wires are to the left side cylinder contacts,rotate the engine backwards until the timing mark on the rotor aligns with the 28deg. mark on the indicator plate in the primary case,at this position the points for the left side cylinder should just begin to open,this is correct timing,if the points are not opening at 28 deg. you will need to loosen the TWO attaching screws in the elongated slots and move the whole base plate so that the points begin to open -- a piece of cigarette paper or similar gripped between the face of the contact points should just release as the points begin to open,tighten the screws.
For the RIGHT hand cylinder,turn the engine as before, RH piston at TDC,valves closed,turn engine backwards until mark on the rotor is at 28 deg., RH points black/ white wire, should just be open,if not, loosen the screw on the sub plate and turn the eccentric screw so that the points just begin to open,tighten the attaching screw. Remove the special washer and replace the stock washer and bolt.Your Haynes manual should show the points diagram and identify the screws that I have mentioned here.
I hope that I have not confused you even more,I have a Boyer unit on my bike so I have not set up points in quite some time,hopefully I have guided you correctly.Good luck, ride safely. James.
PS. Frank Holmes of Franks Brit Bike Barn is in New Hampshire -- Chocorua -- great fellow, does all Brit bike work, phone # 603-323-8310.