The BSA A7-A10 Forum

Technical => Lucas, Ignition, Charging, Electrical => Topic started by: spyke on 19.01. 2011 21:45

Title: auto advance
Post by: spyke on 19.01. 2011 21:45
Hi chaps,

Just fitted my recond mag and have now come to the auto advance unit. Im trying to avoid getting a recon unit and  was quoted 140 ish today from draganfly.
Not sure how to assess mine , i need a new fibre/ali wheel but how much slop should there be between the moving centre and the steel centre bush, how critical is the " taughtness" of the whole cabbodle to good running .I dont want to spoil the ship for a hapeth of tar  at this stage now ive completely done the motor and magneto  but  equally i dont want to replace the whole thing unnecessarily.

Cheers Spyke
Title: Re: auto advance
Post by: Stu55Flash on 20.01. 2011 00:42

The auto advance is more of an on-off switch than a calibrated degree of advance mechanism. I fitted a new fiber gear wheel to mine although the rest is fairly worn it works ok. Watch out for the springs- these need to be stretched slightly when fitted rather than loose as is the case for some new springs. If loose they will come off and you may find them in the sump if your lucky or jammed elsewhere if not. I struggled to find the rivets to fit the fiber gear. Let me know if you cannot find any I have a few leftover.

Title: Re: auto advance
Post by: olev on 20.01. 2011 12:44
I'm just about to rebuild an auto advance.
haven't been able to find rivets anywhere and thought i'd have to make them.
Please email me if you have some you will sell.
Title: Re: auto advance
Post by: A10Boy on 20.01. 2011 13:22
I have refurbished several AR units over the years and think that while there should be some, the amount of play between the inner and outer should not be excessive. The centre will be held on the mag spindle and too much play will allow the fiber pinion to move around relative to the camshaft pinion which drives it and destroy the fiber gear. I would say upto about 25 - 30 thou play on the outer edge of the fiber wheel would be ok. [in my opinion]

You need to take it apart and clean any gunge out of it before you can assess how much play you have. Sometimes they can be stuck together with crud which hides any wear. If it's in good nick, its a fairly easy job to fit a new fiber and springs.

If you want, post it to me and I will take a look at for you, [FOC], if its ok I could give it a bit of an overhaul and fit you a new fiber pinion. PM me if you like.
Title: Re: auto advance
Post by: A10Boy on 28.01. 2011 14:44
Or not.
Title: Re: auto advance
Post by: JohnWB on 02.02. 2011 18:54
I also have an A&R unit that needs looking at. Is there any chance you could give it a check over & possably give it an overhaul.

I sent you an email a few days ago but I guess it got lost in the internet.


Title: Re: auto advance
Post by: A10Boy on 06.02. 2011 19:51
Sorry only just picked emails up. I have replied.