Dynamo Oil seal

RogerJ · Post by **RogerJ** » Mon Jun 27, 2005 10:04 am

I note from looking at earlier topics that there can be problems with geting a good oil seal between teh dynamo and the crank case. Having removed mine (on a 1960 31) to investigate a rather prodigious leak I noticed that the seat on the crank where the cork seal is supposed to go is not particularly smooth - is this normal? It looks as though the case may have been repaired in this area at some time. Is there any "easy" way to make the seat flat without resorting to a total strip or will teh cork accomodate the unevenness?

Thanks, Roger

lawrence · Post by **lawrence** » Mon Jun 27, 2005 6:16 pm

Hi Roger
The roughness should not be a problem. Use silicon sealant (ordinary sort for sealing shower trays etc) generously on the cork and it should remain oiltight (for a few weeks at least) [:)]

Lawrence [}:)]

Biscuit · Post by **Biscuit** » Tue Jun 28, 2005 12:20 am

There is no easy way to make the seating flat. Whether or not the cork will seal on the uneven face depends on how uneven it is, unless you can quantify this, the answer must be - Who knows?.

RogerJ · Post by **RogerJ** » Wed Jun 29, 2005 9:17 am

Thanks for the comments.

There are a couple of raised points that would appear to correspond to "joins" (were the casing halfs cast in one piece or were bits "added" ?). The height is deceptive but possibly around a 1mm or so. I'll try your approach Lawrence and see what happens.

lawrence · Post by **lawrence** » Wed Jun 29, 2005 10:42 pm

Pretty sure the case halves were cast as one piece castings. the dynamo loop always looks fragile to me though so it could have broken off and been rewelded on. Siliocon should seal it. Finding out is one of the joys of classic biking[:(!]

Lawrence [}:)]

Charles · Post by **Charles** » Thu Jun 30, 2005 8:48 pm

I had a similar sealing issue but with my Alton alternator so it is essentially the same fitting and seal to be made in the same place. I drilled out the crankcase and timing cover to 1/4" and tapped the alternator end to 1/4" 26tpi as well. I made up a stud and you can get a lot more pull on it than you dare with the standard 2BA stud. A little silicone around the cork and that leak was cured. This is on 1 1960 31CSR

Charles

Biscuit · Post by **Biscuit** » Thu Jun 30, 2005 9:32 pm

Surely the seating face would have been machined, any lumps or bumps must be due to a welded repair.

RogerJ · Post by **RogerJ** » Tue Jul 05, 2005 5:21 pm

Charles - you indicated that the standard stud was 2BA. Excuse my ignorance but what does that equate to in terms of thickness and tpi? (it looks like 3/16"). I'm not sure there is enough meat to enlarge the hole to 1/4" as you suggested (or am reluctant to drill what looks like a repair anyway).

RogerJ · Post by **RogerJ** » Tue Jul 05, 2005 7:56 pm

Excuse me being a bit thick! 2BA sorted!

Here's to not getting an oil soaked leg when my first attempt at putting it to back together at teh weekend didn't work too well!!