Oil Tap; Magneto Models

[trophy]

My friend (who is not mechanically inclined) has a 1961 Model 31 CSR and he asked me to check out a heavy oil leak from his primary chain case. This brought up queries.
1) The oil level in the chain case was well above the bottom run of the chain and I assume oil would easily escape to freedom via the hole in the rear case for the alternator lead, but as the bike is fitted with a dynamo is the rear case correct??
2) Bearing in mind that the bike has no centre stand and lives on its side stand could this have any bearing on the excessive oil level, or might it be wet sumping? My friend says he does not have to top up his oil tank, which seems to rule this out.
3) Assuming it is wet sumping is there a shut off tap available that prevents starting with it shut? Remember its a magneto model.

All suggestions welcome. Thanks.

[Merlin]

I would not fit a tap, sods law will prevail and sooner or later it will be left shut.

[JimFitz]

Andrew Dove sells taps with an integral earthing switch which kills the mag when the oil tap is switched off. He advertises in trade services on the forum. If you have the ali end cap on your mag with the kill button in the middle you will need to swap it for the bakelite version with the terminal in the middle and you will need to fit an earthing kill switch on the handlebars.

I prefer this arrangement as it makes it a lot easier to reach in an emergency. It is also good practise to test it by turning the oil off at the end of a day's use with the engine running and make sure it stops the engine.

If you like the look of the ali end cap and would like to keep it, I have heard of people modifying it and turning up a nylon bush to replace the push button with a terminal.

Jim

[TrevorCSR]

Your friends bike is most certainly wet sumping.
As there is no oilseal on the crankshaft drive side, when the oil drains down into the sump, it goes through to the chaincase. There is no other way the oil level can rise! IF the sump AND chaincase are not drained before starting, that oil is forced out of the breather, making a mess. Also excess oil will affect the clutch, making it slip. The breather is in that position as normally aspirated oil can get to the rear chain. Makes no difference if alternator or generator (dynamo). Certainly worse with only a side stand. Ask again if your friend checks oil level in the main oil tank before starting.
As others have stated, a physical stop tap is VERY dangerous. There are threads here that will show how to minimise wet sumping. Completing all of these is only possible during an engine rebuild. By that I mean to fit an oilseal on the crankcase drive side, the case will have to be machined, and a hardened spacer made.
So either drain sump AND chaincase after a period inactivity BEFORE starting the engine, or risk forgetting to open tap, with all the expensive consequences that entails.

[trophy]

Many thanks all for your constructive replies and I agree with you on every account. My alternator model 31 also wet sumps (it will empty the oil tank in 4 weeks) so I have Andrew's stop tap fitted and yes, I occasionally prove it works by stopping the engine by closing the tap. This wet sumping thing is endemic with the twins, is there anyone supplying replacement pumps?
Thanks again all.

[clive]

Is he using 20/50 rather than straight 50, that will speed up wet sumping? I find that putting a block of wood under the side stand so that the bike is almost upright slows the wet sumping (not tested empirically).