The bikes original points distributor needed a bronze shim added (18 x 10 x 1.2 mm) above the camshaft driven drive gear to set the end float at 0.2 mm (0.008") as did this replacement distributor.
The difference was there is a steel shim washer and plastic (or similar, maybe Bakelite) shim washer that the main shaft seats on in the bottom of the distributor body (cup)
Both had those two shims except in the base of the body, the original one is raised for them to seat on, this replacement distributor (which still had the original drive gear pin in place looking untouched) is recessed and it did not look worn so there was still a lot of end float.
I put all the parts in the tin at disassembly so do not think a part (larger washer) was lost (who knows)
I machined a 24 x 12.5 x 1 mm Acetyl washer so it also now has around 0.2 mm end float.
The advance mechanism also had end float so it got a 11 x 7 x 0.75 mm Acetyl shim under it and then the shaft was ground so it has maybe 0.015" float.
The washer raising the unit also made it rotate smoothly which is did not do previously.
There is only around 1 mm above and below the trigger arm plate as it passes through the sensor so it needs to be fairly precise to avoid a drama.
It makes a small noise when the plate is at that exit point so maybe it is close enough (being non adjustable now without upsetting the cap pole to rotor relationship)
The ID of the distributor body is machined so is irreversible (it was not round)
Here is the oddity (folk of the if it manages to start it is fine, look away
Every Loop video I have watched (Except for the one with a C5 ignition) which is probably near all of them on YouTube to me sounded like they had a weak cylinder, not bad weak but something odd sounding, this bike was no different, 99% good but something odd, I will call it a lazy cylinder.
I had bought two of the brown FIRE brand caps and rotors from Italy, these are a very nice cap but of course then found the rotor is not going to work in a Moto Guzzi.
I had wondered why the arm on the that OEM rotor was so long but nothing beyond that until I saw that Fiat rotor.
In the Tommy Pettersen video (A big thanks once again for us electrically challenged folk) it says the sensor signals as the plate leaves it but I needed to see what the cap and rotor were doing at that position so I milled this brand new cap purchased years ago (You know to fit after the oil change, Gilardoni's and ride it in 2012 ?)https://www.youtube.com/watch?v=Uo5DqKGnZzs
This meant I could (with the dual read out ignition degree disc on the front pulley) check that each trigger paddle ? (by eye) looked to be parallel with the sensor at exit on each cylinder (yes they are machined so they are parallel entering and exiting the sensor) and then be able to rotate that unit on the shaft until the cap poles were in the best position for each cylinder (before drilling and fixing the trigger plate to the shaft)
I am hoping it will all work with no rework besides setting with a timing light.
Here (to me) is where it gets murky.
This distributor seems to be altered to work in a 90° V twin and that ? is where that long arm on the rotor comes into it (or not ?)
The arm extension (I forget) either adds or takes way to gain the needed 135° (90° / 180°) which a Fiat engine would not need being a parallel twin ?
The narrow and wide (extended?) points cam lobes surely alter the dwell (and ignition coil saturation ?) on each cylinder.
When I put that machined cap on with the points distributor (out of curiosity) it enables the points to be seen and also where the rotor was to the cap poles (at static and fully advanced)
I was amazed the engine manages to run based on the arm to cap pole at those 4 positions and believe that is part of the lazy cylinder sound.
Because the sensor trigger plate allowed it to be positioned at the better all round position then removed for the drilling of the M3 fasteners it should be better but not perfect.
Perhaps this is part of the reason the dual point distributor was introduced.
At this 'point (points distributor) the Eldorado has not only a lighter throttle action (stock springs) but also starts quicker than my F.I Honda Arica Twin. (It would need to do at least one extra cranking turn having a cam shaft position sensor)