Oil holes in the dynamo chain case

[shabashow]

While investigating an oil leak out of the dynamo cork seal area I came across a modification to the section of the inner timing case. Sometime in my bike's past (1952 A10 plunger) someone has drilled two holes in the inner timing case, where the dynamo chain runs. One is in the middle of the chamber, the other is below the large chain sprocket. I can only assume that oil get's splashed from the timing gears into the hole in the middle and drains out the hole in the bottom.
Looking at photos and gleaning information from the haynes manual, owners handbook and the original BSA workshop manuals, the dynamo chain should be greased on rebuild, as there is no other form of lubrication. That's why there's a cork seal placed behind the driving sprocket. During my rebuild. I didn't notice these holes, and was rewarded with lots of oil dripping down onto the right exhaust pipe. At first I thought it was because I forgot to put the little cork seal in, but the source of oil would appear to be from there holes.
Has anyone else seen this type of modification, and would they recommend keeping it? I think I'll get the holes sealed up permanently. There was evidence of lots of hermatite in the area, and I am assuming that the herematite was a previous attempt the seal the chamber from the engine oil.

[LJ.]

Firstly welcome to the A7 & A10 forum Shabashow!

Hmmm this does not sound too good, there is no telling what interference there is to the engine lublication system and besides that, the mess must be horrific  I think I'll echo Dpaddocks wise advice from the gearbox/clutch thread...

It's not always wise to re-engineer the designers' decisions.

So probably what you suggest... Block up those holes! Makes you wonder what ever else previous owners have done. 

[Brian]

A previous owner thought he had come up with an ingenious way to keep the dynamo chain lubricated and it would have done that. Unfortunately it would also have provided a anti rust coating for the outside of the motor as well, ie. oil everywhere! You need to block the holes up and give the chain a good lubrication before you put it in. There are a few different ways of doing this, soak it in chain lube, pack grease around it or cook it [tin full of grease that you heat up]in a chain grease which is what I do. I have often thought about drilling and tapping a small hole underneath that you could take a screw out and squirt some chain lube in occasionaly. The other alternative is to go to a belt drive conversion. Welcome to the forum and enjoy your bike, the plunger models are great.    Brian.

[groily]

Yup, holes need filling, preferably with something better than gasket goo. I'm assuming they're pretty small holes . .
If it was me, I'd get the inner cover off, drill em out to nearest size for tapping for sensible threaded plugs with very small heads on so they couldn't work themselves right through and get into the gear train or worse. Dab of high-strength loctite too. Ali rivets could work too, carefully done.
If you're really brave, you could have a go with Lumiweld or similar - I've just repaired another alloy casting with it (crankcase thread-lugs), and it's good - but you need some decent heat (for the whole casting), and just the right amount of it. The stuff melts at 382 degrees C, ali at 660C, so theoretically there's loads of safety, but ali doesn't tell the inexperienced (me!) that it's about to melt until it's too late. I was nervous, and I still would be if I had to do it again.
Last and best option is to get a decent welder to do the job if you know one.

Can't recommend belt drive too highly - no more noises, no adjustment hassle, no more ali shavings in there from when the chain goes slack, and a step-up in gearing for the dyn is available depending on the system chosen. Best simple  mod I have done (in tandem with upgrading to a modern regulator).

[shabashow]

Thanks for the confirmation, will get the holes welded up asap. Took the case to an local engineering firm that has the capability to do alloy welding, but it's a bank holiday, and he's shut. Will need to wait till tomorrow.
I've replaced my old regulator with a state of the art solid state one, belt drive upgrade is on my wish list, maybe next year.

[RichardL]

Oh, so it is a holiday there! Any relation to our "Memorial Day"? I will add (for the sake of forum conformity) "on which anyone with a working A7 or A10 would be out enjoyng the weather and having a great ride where people drop their jaws because they have never seen that make of bike before and they can't believe that something that shiney was originally made in 1955 and, then, they can't believe that you are actually older than the bike and then they ask themselves "what kind of person am I?" having just walked into a dealer and bought a one-of-thousands bike that anyone could have and then they ask themselves, do those old brakes actualy work and you want to tell them "mostly" and then..."

[bsa-bill]

Well it's confession time folks !!
I drilled holes in the same place but  not to let oil in rather to let it out until I  fathomed out what was going on.
I fitted a SRM belt drive ( can recommend ) at the same time renewed all the bushes in the timing case, the penny dropped when I was looking at my mates bike that was in pieces, I had got the bushes for the intermediate gear mixed up and the bush behind the large belt pulley was scrolling oil through into the dynamo drive cavity to such an extent that it eventually came out at the dynamo, in all this the belt still was driving the dynamo just fine.
I changed the bushes around, plugged the holes with that metal putty stuff and it has been fine ever since

All the best - Bill

[shabashow]

Thanks for all your useful advice and confirmation of my suspicions, folks,
holes now professionally filled by alloy welding and fitted back onto the bike. Only need to time my magneto, which has been fitted with a new armature and condenser and get the headlamp fitting back on and I can try and start her up for her second trip to the MOT station (I hope to get there this time!). I've a problem with the speedo cable, but I'll post another topic for that one.
John