Twin distributer

Can you give a little more details? What bike / what year?

Hello Eddie - are you talking about a Lucas 18D2 distributor on a Dominator ?  Cheers, Howard

There should be a spacer and a copper washer to control the shaft axial play ,washers wear and rotor arm can foul the cap.

The original 'copper' looking washer had dimples in it to allow oil to get to the shaft bearing BUT the dimples are always worn down-hence allowing end float. I have fitted the appropriate steel washer here to control end float (5thou?) which is of course important. I have instigated this when putting the 18D2 (and 18D1) over to Boyer Electronic, where the rotor arm is dispensed with as we go to wasted spark.

The sprocket should be located on the parallel shaft with a very slight taper pin, pushed in hard, unless any one knows better.
If you look at the 18D2 you will see that it is smaller than the Boyer stator plate, hence I have built/sell my own.

i have retained the points  and removed the condensor , fitted a point assist unit from boyer ,with a 12v coil . works well and allows easy timing . points dont wear hardly and if the EI fails you can return to points with a car condensor outside of dissy.  AL oz's system less maintenance and good too.

This is NOT my system to use the Boyer Assist sytem, but if it works -fine. My system remakes the Boyer Bransden pickup plate smaller to fit in the 18D2/1 and hence is the full electronic system as fitted to Commando and any other parallel twin.
The 18D2 was fitted to Triumphs, AJS twins and the same shaft was used on the 18D1. You will find the dizzy body and shafts although they fit together, come from different sources so who knows what you have.
I do not like the idea of a spring washer, if it 'springs' then you could just get lots more end float even if only for a few revs but enough to smash your rotor arm or destroy my Boyer Bransden type pick up 

Between the sprocket and dizzy body is a washer. It was copper with dimples when new from Lucas -195* but replacing with a steel washer bearing in mind 5 thou end float. would seem to do the job.
The stator plate and rotor are made from Boyer Bransden parts so you use the BB amplifier, and remove the rotor and dizzy cap and triple leads, and use twin coils-wasted spark.