Coil Ignition HW Singles Auto Advance

[leobailey]

Trying to build up a complete auto advance unit from part supplied by a kind member from Denmark, help required. The position of the springs I have copied from manuals (still not sure they are in right holes).

My question is about the pins on the underside of the bob weights.

The pins interact with large holes in the assembly base, apparently to limit the movement of the bob weights and therefore the amount of advance. The pins on my unit are not circular, they have a crescent shaped portion missing at their outer edges.
Is this normal ? or is this wear. All help and guides to reference material appreciated.

Hopefully my photos will show what I mean.

Leo Bailey

Originally posted in G3/16 section post here to catch 500cc owners

[1608]

Thought this was answered nice and concisely on the G3 forum?

[leobailey]

Hi 1608

Yes got a good clear answer in the G3 forum, but thought, hey I bet the people with 500's rarely look at the G3 section. So whats the harm in posting where the owners of 500's fish, two or more heads are always better than one. I was in the wrong ? ? ?

[PGGuse]

In case of replacement is needed, may be you can use "ebay" No. 200876838790
Paul in Frankfurt

[leobailey]

Many thanks Paul,
I will study the Ebay item more. but initially they all appear to be from twins.

Best regards

Leo

1608, see others seek to help

[1608]

Because of the commonality of the models I read all the forums. I learn a lot that way too.

[Cerberus]

Worth being aware that the 350 and 500 springs are slightly different. On the correct holes, I noticed that the diagrams in the manuals show the springs in the inner holes, BUT, there seemed to be very little tension in the springs with that configuration. I found my bike's running (350 M16) was really rough, so I moved onto the outer holes and no problems so far (> 6000 miles of use). Also be aware that if trying to fit the springs "in-situ" it is very easy to overstretch them. It's much easier and safer to replace with the whole assembly off, I found this out the hard way.

[Colin F]

If you look at the holes the wear is on the "retarded" side of the pin, so as the timing details are given for fully advanced this wear will not actually make any difference to the timing once the bike is running.

The difference you might find is the bike is slightly easier to start! When I was doing a major rehash of OAF with Malcolm Saggers many years ago one of the objects was to get rid of as many cables as possible, so the choke cable was ditched. As we found that the bike could be a little difficult to start in the cold and because my advance unit pins were badly worn Malcolm redesgined it giving a larger range from retarded to advanced. This has made the bike easier to start with a more retarded ignition when kicking it over but does not affect the running when advanced.

[aobp11]

Hi Colin,
My interpretation is that the wear is at the "advanced" side of the pin. That is, due to this wear the bob weights can go further outwards at high revs, so at the advanced position. You are right that when timing is set correctly in the fully advanced position this wear will only have effect on starting (and low revs).
Albert

[Colin F]

Yes you are right Albert! But as you say set up correctly on full advance there points remain the same!