Replacing ES2 drive side oil seal

Just two drive side main bearings. The seal is on the twins and can be replaced easy enough with the primary off. No oil seal on the ES2, Mod 50 or 19S.

I can send a photo of an ES2 engine I am building, if that helps.

Yes Richard, there is an oil seal on the drive side mainshaft.  I replaced mine on my 1961 ES2 a number of years ago.

It is only accessed by removing the drive side crankcase as the seal is fitted from the inside unlike the twins. Seems a strange arrangement.

The seal seems to have been added sometime early on in the 1959 production run, I have a very early M50 alternator  engine with shop No.C30 which does not have the recess for it but other later 1959 ones do.

The seal itself is not the same one as on the twins and is a peculiar thickness which can be difficult to get, my bearing factor found me some but it took a while.

Thank you, I have just learned something new .When I read about the oil seal I thought no  there is no seal fitted there now I know different

Hi

I too have a 1961 ES2. The last time I replaced the drive side oil seal, no replacements were available from the usual suppliers. From memory, I think the seal should be 4mm wide. Only 5mm wide ones were available. I bought one of those that had a rubber 'sheath' arount the seal 'outer body'. With a stanley knife I peeled/scraped off the rubber on the back of the seal and off the very edge of the front. The modified seal was now only a few thou too wide. I have been running with this for about 12 thousand miles with no ill effects.

Re. the 3 o'clock screw, from memory I think that those holes should all be blind ended, make sure that your screw for the stator carrier is a good fit, a bit of Pipeseal might be an idea, just in case the oil is coming that way.

Another thing that you might try is to put some STP oil treatment in your engine oil, I don't know whether any of the claims made for it are true, but in my experience one thing that it does do is soften up old neoprene oil seals and very often stops them passing, if the seal you bought has been on the shelf a long time it might have gone a bit stiff, certainly worth a try before you pull your bike to bits, it takes a while to work, though so give it time.

......stands corrected:

There is much less pressure involved  with the singles  than the twins because basically  the oil pump is pumping  into an open end, volume of oil is the object,  not pressure.

So use whatever you  like, so long as it seals well enough that oil is spraying out of the big-end,  it will be OK.

... a Commando oil seal there. Seems to work OK.