The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: stanwhite on 11.06. 2018 16:17

Title: Magneto oil seal failure
Post by: stanwhite on 11.06. 2018 16:17
Hi,

   I have an oil leak that appears to come from the timing case end of the magneto. (1961 A10 SA GF).

This could be the gasket, and I am preparing to remove the mag to replace the gasket, but then it dawned on me that there is an oil seal in the magneto.

Would I be correct in thinking that if the drive end oil seal fails, I will get a mag swimming in oil, or is there a drain hole at the bottom of the mag, where this oil could be coming from?

I guess the question is, "what are the symptoms of a failed mag oil seal"? I have not had the contact breaker end off the mag yet either, but that end of the mag is dry.

Please help...  It is my LAST oil leak!!!!!!!!!!!!!!! For now!  *sarcastic*

 Bike starts and runs really well.... (Bet it don't after I put it back together again!).  *grins*

 Cheers,

 Stan.

P.S. If its the gasket, then I am in the right part of the forum?  If not, sorry, should be in the electrical part? I do try... *smiley4*
Title: Re: Magneto oil seal failure
Post by: JulianS on 11.06. 2018 17:33
There are 2 holes in the bottom of a standard K2F magneto as photo.

If a non BSA mag is fitted - without the chamfered edge to clear the crankcase - it will not seat against the rear of timing cover and you will get a leak.

Oil in the mag can usually be found by removing a pickup and checking slip ring with your finger.
Title: Re: Magneto oil seal failure
Post by: groily on 11.06. 2018 18:19
In theory, any oil should EXIT by the hole(s) in the bottom along with unwanted moisture, rather than get sucked in through it/them - but anything is possible I suppose.
However, gasket failure = leak to outside world rather than straight into mag; oil seal failure = leak into mag and only to outside world when the mag  gets filled up! So the former isn't so likely I don't think if the mag's all slimey.
The chamfer point Julian makes shouldn't affect the fit of the flange joint at the rear of the timing chest, but it makes locating the long 'nut' easier on the engine side low down. I've run my A  with several mags over the years, with and without a chamfered bottom edge, and there's no prob with the fit at the flange (swing-arm bike) - not sure if things are tighter on bolt-up 'box versions though. About 65% of mags I see off As are 'correct', the rest are 'whatever', given that all the basics are the same.
If the oil seal has died, there'll be oil inside. Probably won't stop the thing working, but not good all the same. The main earth brush will be a very oily indicator of trouble, being that end, but the cb area may stay dry or dryish for ages. A slightly awkward fix as it requires extraction of the drive end bearing's outer race to replace, which can be a swine to get out sometimes.
Title: Re: Magneto oil seal failure
Post by: stanwhite on 11.06. 2018 20:22
Thanks guys,

                 Couple of real good pointers there. Tomorrow, (I am retired!), I am going to take a look. Brush out, leads out, end off...  Check for oil inside. It is "quite an oil leak" from that area...

If the seal has failed, I will get it rebuilt, I don't know it's provenance...  Get a capacitor upgrade at the same time.

 If not, then the gasket will be replaced, and the mag back on, as the bike runs/starts so well. (First kick!). I already made a "timing pin" that fits in the plug 'ole....

 Thanks again,

 Stan.
Title: Re: Magneto oil seal failure
Post by: chaterlea25 on 11.06. 2018 21:09
Hi Stan,
If the breather cork has compressed a bit, crankcase pressure can and will "make" oil leaks
including forcing oil into the magneto
When you remove the timing cover, see if you can feel any play in and out on the rotating breather
it should rotate a touch on its driving peg
I like to set them so you can rotate the breather easily by gripping the end of the sleeve with pliers but not with my fingers
Even a little play on the breather will cause problems

John
Title: Re: Magneto oil seal failure
Post by: duTch on 11.06. 2018 22:24

 Stan, due to the fact that I'm lazy and like to shortcut things, I wouldn't go too berserk pulling anything apart just yet, apart from the earth brush beside the flange as groily suggested, but just give the flange gasket area a good clean and see if it persists there... then when satisfied you'll have a better idea...
Title: Re: Magneto oil seal failure
Post by: stanwhite on 11.06. 2018 22:54
More ideas for me to mull over, and many thanks, guys.

I'll have a "simple" investigation tomorrow, and if it looks like the mag itself is leaking, that will be a project for next winter. The leak is not that bad, and from what I gather, a mag rebuild can "take a while". I want to ride it this summer! I have now got to the point where I ride the GF with little concern, and get "my feet in a mess" on my japanese bike!!! *conf2*  Happy dayz!  *loveit*

I have a full gasket set, so can replace the breather cork if need be. (Thanks John).

Cheers,

 Stan.

Title: Re: Magneto oil seal failure
Post by: beezermacc on 11.06. 2018 22:56
Magnetos are often full of oil because the oil seal has lifted off its seat so the oil is getting in around the edge of the seal rather than between the seal and the armature shaft. The latter is actually quite rare unless the magneto is very old and has a seal which has gone hard with age and heat. The reason the seal lifts off its seat is because the paper insulation cup has lost its grip or wasn't fitted very well in the first instance; this allows the bearing to spin in its housing which, in turn, loses its pressure on the oil seal's outer edge. This is usually associated with some up/down play in the armature shaft.
Title: Re: Magneto oil seal failure
Post by: stanwhite on 12.06. 2018 01:33
Thanks, beezermac....  More for me to check then!

 Cheers,

 Stan.
Title: Re: Magneto oil seal failure
Post by: duTch on 12.06. 2018 08:47

 Regarding the breather cork, I can't remember if I did it but think I did actually pack it with appropriate thickness gasket paper *behind* the cork (betwixt the cork and tophat) dunno how kosher that is, but I couldn't see anything wrong with the idea, but open to argument  *fight*....

 (part of the reason being; I wasn't going to spend hours searching for the right thickness, then wait 400 years for it to arrive from who-knows-where for a $1 part + $ 4 bags of gold postage)
Title: Re: Magneto oil seal failure
Post by: muskrat on 12.06. 2018 08:54
G'day duTch. Your not alone. I've done that. Between the cork and pinion. I don't condone it but when you have to go, you have to go.
Cheers
Title: Re: Magneto oil seal failure
Post by: duTch on 12.06. 2018 09:39

 
Quote
G'day duTch. Your not alone. I've done that. Between the cork and pinion. I don't condone it but when you have to go, you have to go.

 Bewdy- sometimes the Blues and the Ramoones can work together for the good of mankind.... *smile*




     sometimes
Title: Re: Magneto oil seal failure
Post by: stanwhite on 13.06. 2018 16:48
Happy dayz!!!  *clap*

No oil in the mag, and as the bike starts and runs very well, I am guessing it is the mag to inner timing case gasket. And I have one of those  *smiley4*

The earthing brush was dry, and about half inch long, so I guess that will last a while, as the current through it must be very small.

Have breather cork disk, and gasket material of various thicknesses, should I need to ensure that the breather is not a loose fit...

Have learnt a lot from you guys, thanks...  Ready for the next "bit of hassle...!"

Cheers,

 Stan.
Title: Re: Magneto oil seal failure
Post by: duTch on 13.06. 2018 17:11

 
Quote
......Have breather cork disk, and gasket material of various thicknesses, should I need to ensure that the breather is not a loose fit.......

 Yes, definitely not loose or any end play; maybe *just* able to rock it on the locating peg after button up, but I'm sure someone knowing better will confirm....
Title: Re: Magneto oil seal failure
Post by: Greybeard on 13.06. 2018 17:27
When you remove the timing cover, see if you can feel any play in and out on the rotating breather it should rotate a touch on its driving peg
Surely the peg on the breather pinion more or less fits the hole in the top-hat piece
Title: Re: Magneto oil seal failure
Post by: muskrat on 13.06. 2018 21:26
G'day Stan.
The correct cork thickness will give about 0.010" crush when the inner timing cover is put on. You can trial fit the cover without any cork and test the in out movement of the breather. That will give you a thickness of cork.
Cheers
Title: Re: Magneto oil seal failure
Post by: chaterlea25 on 13.06. 2018 21:32
Hi GB,
The peg is not a tight fit in the breather sleeve, so its possible to move it back and forwards a little

John
Title: Re: Magneto oil seal failure
Post by: stanwhite on 13.06. 2018 22:21
Thanks guys, more great info...

Muskrat, you answered another query, in that the inner timing cover needs to be removed to fit a cork. (I have an inner gasket, no great shakes...).

I'll dry fit the inner gasket as well to gain the measurement?

I do have the Haynes manual. It is useful. Don't think it is great though...

 Thanks,

 Stan.
Title: Re: Magneto oil seal failure
Post by: duTch on 13.06. 2018 23:15
 
Quote
....I do have the Haynes manual. It is useful. Don't think it is great though........

  *whistle*

 I knew I could count on the others to finish that for me.... ..(more)*whistle*