Manual advance system

[AlaskaJoe]

Hello all! Thanks for adding me to the group and for helping me tap into the collective knowledge here.

I just brought home my first British bike, a 1957 Road Rocket with the a10 motor. I am so pumped as I’ve wanted a preunit BSA for a long time.

First issue I need to fix to get it running is the manual advance. I actuate the lever on the handlebar and can see the cable flex and slack, but the points plate doesn’t move (pic attached). I suspect it’s stuck from sitting and I am seeking advice on the best and least risky/intrusive way to break it free. All advice and tips are appreciated! Thanks again for the add!

[Billybream]

Hi.
Would be best to release the cable from the lever and then unscrew the housing on the mag, you will then expose the spring and engagement paul, I would then remove the points via the centre brass bolt, try some WD 40 around the cam ring to try and free it off, you will see at the bottom of the cam ring a felt oiler, the cam ring should rotate quite easily and suspect it will be corroded. With the  cable disconnected and the points off, you should be able to lever the cam ring out of the mag. Have a look on the Priory Magnetos web site page for detailed information, Andrew is a forum member here in the UK

[CheeserBeezer]

When you say the 'points plate' doesn't move, are you expecting the points to move or the cam ring? The cable is attached to the cam ring which should rotate clockwise when you move the cable to the 'tight cable' position. If the cam ring is stuck, I would expect the cable to go very loose when you move the lever to the slack position.

[AlaskaJoe]

Hi.
Would be best to release the cable from the lever and then unscrew the housing on the mag, you will then expose the spring and engagement paul, I would then remove the points via the centre brass bolt, try some WD 40 around the cam ring to try and free it off, you will see at the bottom of the cam ring a felt oiler, the cam ring should rotate quite easily and suspect it will be corroded. With the  cable disconnected and the points off, you should be able to lever the cam ring out of the mag. Have a look on the Priory Magnetos web site page for detailed information, Andrew is a forum member here in the UK

Cheers, Billybream! This all sounds quite straightforward and I’ll give it a go and report back.

[AlaskaJoe]

When you say the 'points plate' doesn't move, are you expecting the points to move or the cam ring? The cable is attached to the cam ring which should rotate clockwise when you move the cable to the 'tight cable' position. If the cam ring is stuck, I would expect the cable to go very loose when you move the lever to the slack position.

Thanks for the clarifying question, Cheeserbeezer, I’m thinking that my terminology is off. If I understand the manual advance system correctly, I’m thinking that I should see the points mechanism move clockwise or anti clockwise as I actuate the handlebar lever. Not that the points themselves move, but the entire plate rotates. Perhaps that’s called the cam ring (forgive my ignorance). The picture is the bit I’m referencing. Total BSA newbie here.

[chaterlea25]

Hi Joe,
It is only the steel cam ring that's outside the points and inside the alloy housing that moves, maybe a 1/4 inch or so

John
 

[Swarfcut]

This method of altering the timing can seem strange as in more conventional systems the whole points assembly moves in relation to the cam. Here it is the cam ring  that moves to alter the timing. The whole points assembly rotate clockwise when the engine is running.

  Moving the cam ring anticlockwise advances the timing.... Pulling the cable retards the ignition for starting and slackening the cable allows the return spring in the plunger housing to move the plunger and the cam ring back to the fully advanced position.  Referred to as "Slack Advance". Chances are the whole mechanism is seized but it's a simple clean up job. Points plate seats on a keyed taper, treat with care. The points assembly pulls off after releasing the    center bolt with "lefty-loosey" thread. The cam ring will then draw out after freeing off. To reset the timing is a whole different ball game, let's hope just a little bit of TLC  gets a runner. Static timing is set at full advance, the normal running mode. Retarding the timing by pulling the cable aids easier starting by reducing kick back.

Swarfy.

[RichardL]

Well, I'm surprised no one with more manual advance experience than I (really, zero expreience) would not have posted a picture showing the ring and direction of movement by now. The arrow from the outside points to the cam ring. Counterclockwise moverment advances the spark, as Swarfy notes.

Richard L.

[RichardL]

Oh, here's a tiny tip about a tiny tip. Looking at the retaining spring that holds the points arm in place, there's a bump out there that normally fits over a tiny tip on a tiny button that sits in the points arm. If there is even one still there (it doesn't look it), try not to lose it. I don't think it is an available part. I made myself a new one from a plastic rod on a lathe.

Richard L.

[AlaskaJoe]

Ok, progress report. I removed the cable from the handlebar mounted lever and unscrewed it from the mag housing. Then removed the brass screw and the points came right out. Lots of corrosion on the outside of the points (see pic) I suspect this shows where the manual advance plunger was stuck. So, is the remaining ring on the mag housing what is supposed to move? Also, that plunger where the cable end connects won’t go back down into the housing. Is there a trick to lining it up somehow? First things first, I need to get that ring moving. Thanks for the ongoing advice!

[Billybream]

Hi Joe.
Nearly there, pic attached will show how control plunger and cam ring work.
Suggest try some WD40 around the cam ring, then gently grip the plunger and push and pull until cam ring moves, then pull cam ring out from the housing and clean up surfaces

[Swarfcut]

The cable operated plunger lower edge engages in a slot in the cam ring, as the plunger is moved up and down the cam ring rotates in the magneto end housing...... At least that's what it should do.

There is a narrow gap behind the cam ring, just wide enough to get a pick to ease the cam ring out. As suggested WD (and maybe a heat gun) will aid removal.

BSA Service Sheet 801 provides more information about the magneto but does not include manual variant. Sod's Law indeed.

Swarfy.

[AlaskaJoe]

Thanks all for the detailed advice and pics. I’m moving really slow as I don’t want to damage anything. I reckon it’s a bit harder to find these parts of I break them.

One additional question for the group. I’ve gotten advice from a couple folks on using WD 40 to help break this ring loose. Is it ok to use like a PB blaster or kroil penetrating oil or are you all suggesting WD 40 because it’s easier on these parts? My goal is no damage, but I’ve had great luck in other bikes using those penetrating oils/sprays to break up seized bits.

[Bsareg]

I think we tend to use the term WD as a generic term for any penetrating fluid, a bit like Hoover for vacuum cleaner. Sounds like you're progressing fine. You're right to be careful, some spares can be difficult to find.

[Rex]

Regarding WD40, I reckon Kroil, Plusgas etc are far far better than WD at freeing things. WD is OK as a spray-on lube but useless as a release agent.