Breather pipes from crank and oil tank

Hi Peter,

I can suggest two possible solutions (one of which will appal the Green lobby!) :-

1. Run a pipe to a small tin, or plastic, container tucked away out of sight.

2. Route the breather pipe onto the rear chain (as per early Nortons). No more expensive chain lube!

On my 99 the crankcase breather had a copper pipe pointed straight at the gearbox sprocket in the hope that oil mist would lubricate the rear chain. It did on long, hot summer runs (over 150 miles). Not much use on shorter cold runs though. The oil tank overflow/breather should produce almost nothing, but you can route it to a drilling in the top of the chain guard, again to help lube the chain. It only really works if you accidentally overfill the oil tank then you find that within a mile or so you have oiled your chain, swinging arm and rear tyre...

Later models with an oil separator tower in the oil tank routed the crankcase breather to the oil tank and then the oil tank breather to the chain guard. This is quite good if you get occasional wet sumping as you pump oil from the crankcase to the oil tank rather than over the garage floor. Yes, I know I should drain the oil from the crankcase before starting but sometimes I really cannot be bothered, especially if I am in a hurry. Not that my 99 wet sumps, perish the thought!

On my 1963 88 I take the breather pipe from the crankcase to the oil separator tower on the tank as seems to be expected, then an outlet from the rear of the separator tower down the frame behind the gearbox. This avoids having to drill the mudguard to run a pipe to the back of the bike and seems to work, but if oil rather than fumes were to escape from the tank it would be a good way of lubricating the rear tyre! I notice there's a hole in the top of the chainguard near the front, which I now realize from Gordon Johnston's reply must have been for the breather. As I seem to get more water vapour than oil mist coming out of the breather, this would be a good way of making the chain rusty.

I do get mayonnaise on the oil filler cap and globules of water in the bottom of the tank when I drain the oil, so a catch pot might be a good idea between the breather outlet and the tank, if I had room for one, but I've got an air filter in the space between the battery box and the oil tank.

Hi Rob, I'm a bit surprised you suffer from mayonnaise and water in your oil - not a common Dominator problem. It's usually associated with short journeys. Up here in in the wilds of Scotland, we don't suffer from an excess of warmth or sunshine but I don't have any condensation in the oil - when the chain gets rusty it's because of masses of salt spread on the roads locally. At this time of year the chain has to be oiled at the start and end of every journey. Norton chainguards are nothing like as good as BSA ones for keeping road spray off the chain...

Gordon.