This Forum is now CLOSED use the link to get more details viewtopic.php?f=3&t=13924#p102587
#88621
Having difficulty refitting auto-advance unit on my 1957 Bullet. You may have seen from previous posts I had the magneto repaired and am very much learning (or not) as I go along. My auto-advance unit has a single bolt running through it given its a 1957 bike (later versions I understand were modified) which is tightened up anti clockwise to pull the unit off the magnet (Lucas SR1) shaft through an external thread but tightens up clockwise onto the magneto shaft itself by way of an internal thread inside that bolt. This combination frees the auto-advance from the magneto. I am wondering in refitting do I remove the bolt from the auto-advance unit completely and then push the unit onto the magneto shaft. Once it is locked on by this means (as I am assuming in suggesting this there is some sort of inner ridge inside the auto advance unit to match the magneto shaft somehow)) do I then reinsert the bolt and tighten up clockwise? Sorry if this makes little sense to those more mechanically minded than myself but have tried leaving the auto-advance fully assembled with bolt installed but its very loose and even if it binds on the magneto shaft it spins the magneto rotor, won't tighten and disturbs the timing set up as advised in my workshop manual. This states set the points gap at 0.12 and then advance the cam clockwise to about 2 thou when the feeler gauge will just pull out. Auto-advance unit secured to fully advanced with engine 1/2 inch before TDC. All my timing marks on the relevant wheels are then lined up. The manual is unclear as to how to refit the auto-advance it just says try to avoid the unit slipping on the shaft. I know i could try this without asking but don't want to damage anything given the age of the parts. The magneto had failed so at least in taking it off have solved one problem to create for me another. Any help appreciated as usual. Trust you are all keeping well in the current situation. Hugh
#88626
Hi, check that the thread is not stiff. just hold the rotor gently and the auto advance should just screw up with you fingers and finally tighten with a spanner. It sometimes is a three handed operation. Remember to take up any backlash in the timing gears. You may have to take several attempts before you get the timing correct. I take it this is an SR1 magneto? Vince
#88663
I bought an otherwise good SR1 mag where the 3/8" BSF thread on the drive end of the shaft has been a little bit chewed, and it will need cleaning up with a die or die-nut before the auto-advance unit I have for it will fit properly. Might be worth checking the thread on your SR1 too in case there are any burrs or snags. Check the internal thread of your auto-advance unit too, in case it needs cleaning up with a plug tap.

As you managed to get the magneto off for reconditioning I doubt if it's too bad, though

A.
#88665
I may not be understanding your problem correctly - but I had an issue where the nut bottomed out on the shaft and became tight but it still allowed the ATD to rotate on the shaft.
This was because I didnt fit the 'C' clip washer!
you could check that the tapers are not damaged or burred which would prevent the ATD from 'locking ' onto the shaft.
have you tried fitting the nut onto the shaft without the ATD? it should go all the way on with just finger pressure of course. if it wont go on with fingers then do what Adrian suggests.
Attachments
s-l1600.jpg
#88802
Thanks for the advice/help above. I am going to have another go over the next couple of days. I have spent a little time on the points gap in the meantime which Lucas advise is 0.012 as opposed to my workshop manual which states 0.015 and as in a quandary polishing the bikeImage. I have removed the AA unit bolt and the internal thread screws easily clockwise on to the magneto rotor when separated from the AA unit. Observable thread look good/clean. The external thread on the bolt also does up anticlockwise easily. I must be doing something stupid. Having pushed the AA unit on the magneto rotor I have already inserted the bolt into the auto advance to engage the external thread by turning this anticlockwise which as you know is used to remove the AA unit from the magneto and then attempt to screw up the nut clockwise by hand to engage the rotor and the thread internal to the bolt. i did get it on the last time I tried but there was quite a distance between the C washer and the bolt head which rather worried me. It was all rather loose. There was a gap between the back of the AA unit and the timing case but the AA unit had engaged with the idler gear. The AA unit must have engaged the magneto rotor as it could not be pulled off without winding the external thread anticlockwise. I have someone hold the magneto rotor to stop it turning.

I considering setting the the points on having read on the internet from a restoration of a 1957 500 Bullet in setting timing to use TDC -1/2 inch but set the points as just about to open with AA unit tied with wire at fully advanced. This seemed very authoritative as the author had posted various pictures of this and other restoration and came across quite well. He also advise the 0.012 in line with Lucas SR1 manual. This contradicts my workshop manual which says 'rizla; gap as they are about to close rather than about to open but still with AA tied in fully advance position. Not sure which one to use in my next attempt.

One final puzzle I get a good spark at the points but when restored my magneto man said the mag was timed at south polarity and he corrected it to north. Meant o ask what effect this had but forgot as everything was sparking well.

Keep well all. Hugh

Shop for accessories at Hitchcocks Motorcycles