Magneto Auto Advance

[Stu55Flash]

Can anyone help with my 1955 A10 Plunger Flash

I've finally started stripping the engine as far as undoing the auto advance off the end of the magneto. Instead of withdrawing the advance the centre bolt has undone so far and then stopped without bringing the advance mech with it. Is it possible to leaver the mag out the back. Will the advance mech pull off against the case without damaging the bakalite cog? 

Any ideas welcome.

Stu

[trevinoz]

Stu,
          It should unscrew so far, meet resistance and further unscrewing should release the gear from the taper.

Trev.

[Stu55Flash]

Hi Trev

It unscrews so far and then just turns. The bolt head is 10mm off the top of the advance mech but then just turns. I think the shoulder has pulled through the mech without the gear pulling off the shaft. Could this happen? With not having one apart before I dont know how it goes together or comes apart. There is a horse shoe washer and cover plate that have come off from under the  nut head. I don't know if it was assembled correctly as the engine has only been put together loosely. I have never had the engine running in the bike.

Stu

[trevinoz]

Stu,
           It was probably buggered when the last bloke fitted it!
I have never had this problem [yet]. Time for a little experimentation.
A puller won't work as there is nothing to pull against unless you get the nut out.
Try pulling it outwards and turning it clockwise as it has a left hand thread on it's shaft, that's the way they are assembled.
Trev.

[A10Boy]

If you can get the nut out - which looks like a bolt and as trev says has a left hand thread which engages into the unit when it has unscrewed off the shaft, - you could grind off the remaining outside threads and screw it back in onto the mag armature shaft. This will then give you something to pull against. A small two leg puller could then be used. You will probably need to replace the Fibre gear anyway.

Certainly dont try to lever against the cases.

Andy

[Stu55Flash]

Hi thanks folks

Now got it off not quite sure how! Tighten it up clockwise then unscrewed it anti clockwise and it came off. The bakalite cog has a tooth missing [not my doing]. I've seen these on the Dragonfly web site. Are they for the manual advance or can they be replaced?

Stu

[MG]

Hello Stu!

If you want peace of mind, better buy an aluminium wheel. Draganfly has them listed, but the part's description says "fibre wheel", while the photo shows the Dural one. You'd better ask prior to ordering I guess.

http://www.draganfly.co.uk/shop/pd-2060969223.htm?defaultVariants={EOL}&categoryId=0

I'm using aluminium wheels from SRM, these are not cheap, but they work a treat. I recall some members complaining about wrong teeth profiles, so the wheels were not engaging properly.


The pinion on the auto advance unit can be replaced, it's not a big deal.

Here's some information about disassembly:
http://www.audioworld.net/BSA/forum/index.php/topic,1744.0.html

Kindly provided by your best friend, the forum's search function.  


Cheers, Markus

[A10Boy]

Stu
Good news its come off.

The gears are fiber not bakalite. You can replace them yourself, but first check that the center moves nicely inside the outer bit, some are seized but most are worn badly. If its worn the gear wobbles around and that's what damages the teeth, also check that the tangs on the stops are secure, I've seen some missing or about to break off. If its badly worn you can get them refurbished. I wouldn't be tempted to use one with excessive play.

On the rear of the unit is a collar fitted over the center, it has 3 or 4 punch marks on the joint, lightly drill the punch marks, put the unit in the vice carefully holding it by the scrap gearwheel, and get some grips on the collar, rotate it and it comes off.

Next you can pull the center from the outer saving the weights and springs. Drill out the four rivets holding the gear wheel on, replace the wheel, fit new rivets [3/16 mid steel] and as they say, assembly is the reverse of dismantling. You will need a new center nut too.

Make sure it all moves without binding or you will have problems.

Any questions let me know.

[Stu55Flash]

Thats spot on

I will order up fibre or ally cog and rivet it in. Stripped the barrel and clutch off. Barrel and pistons spot on. need to split the case to clean sludge trap. End float on crank is 10 thou measured with DTI seems an awful lot but haynes says 24 thou limit? Pleased so far as not much cost and time involved so far! High hopes.

Stu

 

[trevinoz]

Stu,
           I would tighten up that end float considerably. I aim for .001"-.002".
Definitely clean the sludge trap and make sure the timing side bush is a good fit on the crank. .0015" clearance is perfect.
Trev.

[muskrat]

G'dat Stu,
                that's 24 thou BIG END side play not crank end float. Ditto what Trev says.
Cheers

[bsa- bill]

Yep crank end float 3 thou max, if you can do it - "measure many times take bearing off once" - is good or measure old bearing and new one accurate if you can then do some sums with the difference and existing crank end float.
Good luck with it anyway

[A10Boy]

Isn't that 3 Thou max on a re-build ??

[bsa- bill]

Isn't that 3 Thou max on a re-build ??

Isn't that what we are talking about

need to split the case to clean sludge trap. End float on crank is 10 thou measured with DTI

This might be of interest Stu item 270609576884 on Ebay

[A10Boy]

Stu
I have a couple of good re-con A/R units if you are stuck.