I think I got my problem figgered out but don't know what to do about it. I had ask about the mag. pinion hitting the oil seal. Someone suggested to put pinion on and leave idler gear off and see if mag is binding when turned. It isn't and I think all is good. Now I definately think the rubber just in front of the lip part that seal is hitting. Not the hard OD part and that is why it doesn't bind. Here is why I think so.

I have tried to time that mag. a dozen or more times. I get everything set up and tighten the pinion, then check and the timing is way off. After a couple times I decided to set timing initially off in the opposite direction as it was ending up, thinking it would be right when it moved. I didn't think pinion was moving on shaft because I was tapping and sticking it on, but then I thought it must be. No, that didn't work! Then I decided to get everything set up, stick the pinion by tapping and not tighten it up and then recheck. Guess what, timing is off and I know pinion didn't slip on shaft because I didn't tighten or attempt to turn it. I think, what now . I check point gap and it is way too wide. Then after head scratching I remember when cleaning up the mag that I could move the shaft in and out just a tad (thrust). I now can't move it at all, no thrust. So I take pinion off once again and I have thrust and point gap is correct.

Now how to fix this? Put the pinion on and reset the points, or what? When I put pinion on it is pulling shaft therefore opening points. If I am right about this, if I had a thinner seal, then it wouldn't pull the shaft because it would never touch it. Does anyone have a seal number that could be bought local that would be thinner?

email (option): ldj1002@yahoo.com

From memory, one of the guys has commented on this problem in the past.

It could be that, over the years the mag pinion has been lapped in so often that it is now sitting too far along the shaft. Therefore, you cannot really tighten it up well enough to keep the timing in position.

Is the solution to take a few though off the back face of the pinion?

Before you do this wait for a few more replies as more and more I am becoming convinced that I should not be let loose with a spanner!

email (option): sacombsashtrees@hotmail.com

I had a similar problem as I had lapped the taper so I removed the nut that secures the fibre dynamo drive pinion and skimmed a mm or so off to ensure the magneto drive pinion seated on the taper well. So far it seems to work ok.

Note it also is worth checking the location of the magneto assembly in terms of height above the magneto "pedestal" and using shims as necessary so that the magneto drive is about concentric to the oilseal housing or you'll have difficulty fitting the drive pinion and get noisy gears.

Incidentally I've just had my mag armature rewound and a new condenser fitted and it has transformed the starting and running.

Rick

email (option): rick.howell@talktalk.net

From memory, one of the guys has commented on this problem in the past.

It could be that, over the years the mag pinion has been lapped in so often that it is now sitting too far along the shaft. Therefore, you cannot really tighten it up well enough to keep the timing in position.

Is the solution to take a few though off the back face of the pinion?

Before you do this wait for a few more replies as more and more I am becoming convinced that I should not be let loose with a spanner!

[/quote]

If I can't find a thinner seal, I like the idea of removing a little off the back face of the seal. To be sure we are on the same page, that is the part of the pinion where the lip of the seal rides. Take some off allowing the pinion to seat on the taper without touching the seal.

email (option): ldj1002@yahoo.com

I check point gap and it is way too wide. Then after head scratching I remember when cleaning up the mag that I could move the shaft in and out just a tad (thrust). I now can't move it at all, no thrust. So I take pinion off once again and I have thrust and point gap is correct.

Now how to fix this? Put the pinion on and reset the points, or what? When I put pinion on it is pulling shaft therefore opening points. If I am right about this, if I had a thinner seal, then it wouldn't pull the shaft because it would never touch it. Does anyone have a seal number that could be bought local that would be thinner?[/quote]

I hate to be the purveyor of bad news but I believe your magneto is seriously damaged. There should be no in out movement of the armature. I think the driven end mag bearings are crushed and/ or the housing damaged.
This could have been caused by tightening pinion nut up while pinion has been held off the taper by either a too thick oil seal or too large a gap between mag and back of timing chest. It will require an expert and probably a lot of money to fix plus the underlying cause will have to be investigated.

I hope i'm wrong but at least you know the worst.

I check point gap and it is way too wide. Then after head scratching I remember when cleaning up the mag that I could move the shaft in and out just a tad (thrust). I now can't move it at all, no thrust. So I take pinion off once again and I have thrust and point gap is correct.

Now how to fix this? Put the pinion on and reset the points, or what? When I put pinion on it is pulling shaft therefore opening points. If I am right about this, if I had a thinner seal, then it wouldn't pull the shaft because it would never touch it. Does anyone have a seal number that could be bought local that would be thinner?[/quote]

I hate to be the purveyor of bad news but I believe your magneto is seriously damaged. There should be no in out movement of the armature. I think the driven end mag bearings are crushed and/ or the housing damaged.
This could have been caused by tightening pinion nut up while pinion has been held off the taper by either a too thick oil seal or too large a gap between mag and back of timing chest. It will require an expert and probably a lot of money to fix plus the underlying cause will have to be investigated.

I hope i'm wrong but at least you know the worst.
[/quote]

Keith,
That had crossed my mind. However when I turn the shaft it is smooth and I grab the shaft and try to move up and down there is no movement. In the shop manual there is a exploded view of the magneto. Manual tells very little about the mag. It does show a shim. No where it tells how to set thrust or how much there should be if any. Where the pinion fits, I can put the nut there and pull and can pull slack out. I turn loose and it goes right back like it is spring loaded. I don't see a spring that holds it forward. What keeps it forward??? I'm thinking maybe the magnetic field.

Edit--update: I did more digging on internet and found more about the magneto. There isn't to be any thrust and you adjust by adding or removing shims. I still wonder what makes the armature return forward? Anyway I going to remove shim and get that end play out. I am still going to get a thinner seal if possible.

email (option): ldj1002@yahoo.com

If the taper on the mag pinion is now too loose to fit the taper on the shaft, then you wont be able to tighten the mag pinion bolt tightly enough to prevent the pinion from moving on the shaft.

My understanding is that you take some metal off the inside face of the mag pinion itself. Having said this I haven't had my pinion machined.

I have always found it easier to do the timing with two people. One holds the points still, whilst the other gives the mag pinion a careful tap with a mallet and then tighten the mag pinion bolt.

email (option): sacombsashtrees@hotmail.com

The mag armature should be shimmed within the body of the mag to have minimal end float...If this is not correct the mag should be stripped and the problem addressed...

Once this has been done and you are happy the magneto is set up correctly check the fit of the drive gear...

As far as the mag drive gear and the taper are concerned, fit the drive gear to the mag (off the bike) and look to see whether the rear face of the gear is touching the front face of the clutch locknut..This nut has a shoulder on it which you will see as the mag drive end cover doesn't cover it...

If there is contact between these two pieces the taper will not seat correctly...

In that case you can machine/grind a little material of the rear face of the drive gear until there is visible clearance between the two components...

When you have that, then lap the drive gear to the armature taper with some fine grinding paste to ensure you have a good 'seat' between the two parts...

email (option): ian@wright52.plus.com

Took the mag off and took point assembly off, then took the end plate off. There was 2 shims there and both surfaces were corroded. I removed the shims and still had too much end play. I removed it again and used wire brush and l cleaned up the mag. surface. I Then used a file on the end plate. It was really corroded and warped. it was high at the 4 bolt holes. I worked it down, then tried and still had a little end play. Took back off and worked it more. The file took quite a bit off around the bolt holes and was barely touching between the holes. I put back together and very little if any end play and there is no drag, so not too tight. I suppose through the years corrosion formed between the end plate and seal and pushed it away from mag and warped the end plate. That took care of end play.

Now for my worries about the seal:
With mag. off I measured distance from back face of sealing surface of pinion to cover on mag. Then with mag installed and and pinion off I measured distance from face of seal to cover no mag. I couldn't get to it to measure really good but I think that pinion is barely touching the face of the seal. I think I located a seal local that is 1/4" thick instead of 3/8". That seal will for sure clear. I think I should get the thin seal.

email (option): ldj1002@yahoo.com

...... It was really corroded and warped. it was high at the 4 bolt holes. .......I suppose through the years corrosion formed between the end plate and seal and pushed it away from mag and warped the end plate........[/quote]

Unless I'm mistaken, that sounds very much like the damage caused by people who use a hammer on the shaft to break the taper which is a complete no no. I wouldn't do that "tapping it onto the taper" thing you mentioned either.
I've always put a spring washer under the nut to stop the timing going out as I tighten it, then once fully tight & the taper is holding I just undo the nut & remove the spring washer & replace the nut.

If you look in a postwar BSA parts list (49-58 for example) a spring washer is specified for fitment under the magneto drive gear retaining nut...

I haven't looked at a wartime list yet to see if that is the case there also...

Despite that I never fit one myself and I haven't found omitting it to be problematic....Ian

email (option): ian@wright52.plus.com