I have a 1943 M20 that I have been in the process of rebuilding. I have ordered 2 oil seals 65-2316 for the Magdyno pinion, from two different suppliers, but neither seem to fit properly. They do not fit snugly in the engine side of the timing case where there is a raised ring. I have rebuilt a number of BSA and Triumph engines and with those the oil seals are always a press fit. With my M20 it is lose. Am I getting the wrong size seal or is something else amiss.

Thanks

Hi Andy
I am in the process of rebuilding my 1942 M20 magdyno too (long slow process in my case!!) I have a standard oilseal 20 38 7 mm which fits the crankcase and gear ok it replaces a fibre thing which was in there. Somebody here posted the size some time ago. I have the mag sparking again but have lots to do on the gene before I refit - it has been pretty well wrecked and has never worked while I've had the bike. Had lots of trouble getting the drive end bearing for the mag - they come in 2 sizes and mine is the big one. (Anybody got a spare E3HM gene they want to sell?)
Seasons Greetings to all
Doug W

email (option): watsond @ xnet.co.nz

I've got a spare E3HM-LO dated 1946, it's for rebuild, but it dosen't look too bad, the commutator looks in pretty good condition, it has the gear on the end and the band to cover the brushes, but not the bakelite end cover, if you want it please PM me

email (option): davmax@ntlworld.com

It appears that my thread has gotten off-topic. I am not rebuilding my Magdyno but I am in the process finish my engine rebuild and putting the bike together. I am looking for information about the oil seal for the Magdyno pinion.

Thank you

Hi Andy..If these bikes are run with the magneto straps loose as well as wearing the mag mounting platform and slots in the crankcase as the mag moves about, they will frequently wear the magdynamo seal housing as well. Once worn they are usually oversize and 'out of round'
You need to measure the housing diameter to determine if that has happened...and it sounds like it has.
I remachine the seal housing oversize and fit an aluminium sleeve to restore it to the standard size...However, that requires a total engine strip. The REME solution was even more radical..they machined a large hole that removed the entire seal housing and fitted a machined brass housing that had the seal housing machined into it. The brass housing was held to the crankcases by three screws. This mod is frequently found on ex WD cases so it wasn't an uncommon problem.
If you clean the housing thoroughly with thinners you can glue the seal in with Araldite/Liquid Metal or similar, taking care to ensure it is positioned centrally in relation to the mag armature. This will work OK and provide a temporary fix until you have the engine apart next time...
It is something that is easily overlooked in the early stages of an engine rebuild but causes a real headache once the engine is assembled... ...Ian

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

Ian, thank you for the response. I too also thought about gluing the seal but wondered about the longevity of such a repair. Upon further investigation the seal retaining area is worn unevenly, which would explain why the seal does not fit properly. Unfortunately, I did not notice that during the rebuild.

Hi Andy..Easily overlooked...I got caught many years back and learnt to check this at stripdown. I always look on the positive side with these things..it's another small piece of M20 knowledge gained...Ian

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

Hi Andy

You may be able to use an inch and a half od seal which is 38.1mm od.

Drop me an email if you struggle and I will help you out


Darren

Also Doug.

If you need the bearing, let me know what it is, or dimensions and I should be able to source one for you.

email (option): dwrudd@lineone.net

Hi Darren
Thanks for the offer - I found one in Australia ok it is a N3048 15x37x8 cup and cone and a bugger to fit with the insulation.
Regards to all
Doug W

email (option): watsond @ xnet.co.nz

The original type seal with its shape that goes nicely into the back of the pinion is nicest to use.
so on a machine i temporarily fixed recently, i used that super strong modern windscreen bonding system, the rubbery stuff goes on after a (very important) special primer is painted to the cleaned metal.
Effectively bonding the seal in.
I'm confident that stuff is oil proof & was a bit concerned that using harder glues might be a higher risk if any of it came adrift & went through the timing gears.