Oil coming out of the Breather hose

There is oil coming out of the breather hose then it is dripping out the bottom of the air filter housing, does this mean im getting pressure in the crankcase ??? plkease help

I'm no expert on this but I think i'm learning from reading the increasingly numerous threads on this subject.
Here is my understanding of the subject:

1. The motion of the pistons must inevitably tend to pressurise the crankcase.
2. There is SUPPOSED to be air (and possibly some oil, especially on Combat models) flowing through the crankcase breather hose, to relieve that pressure.
3. This air/oil mixture is routed into the oil tank where it should not cause any trouble.
4. The oil tank in turn also has to breathe. On early models like mine it breathes into the air filter housing, where the air can be inducted into the carburettors. However, condensed oil within the tank breather pipe can tend to drip into the filter.
The tank breather was re-routed on later models, probably to overcome this problem. Oil in the filter can be a nuisance, but it doesn't necessarily indicate a major problem.
5. Overpressurisation of the crankcase usually manifests itself by oil being forced out of the crankcase joints, barrel joint, oil seals, even into the primary drive.

If you don't have symptoms of excessive crankcase pressure, try not to worry about the oil in the breather hose.

Cheers
Martin

Martin about covered the scope of it except possible ring blow by d/t gap fault or bore wear. Blow by past the push rod tunnels is not un heard of in past nor for decades to come.

I did a small test one day a couple years ago. I have an early bike with the central oil tank and a times breather, so it may not apply to your issues at all. Anyhow, I let the bike wet sump for a day or so, still plenty of oil in the tank. I removed the timed breather tube from the top of the oil tank, taped it in a large pill bottle and started the machine. There was an initial burst of oil into the pill bottle followed by some sputtering oil, followed by oil vapor. Allowing the bike to run about 4-5 minutes, I ended up with maybe a teaspoon of oil in the bottle.

I also have routed my oil tank breather into a pill bottle and after a summer of driving, I have less than an ounce of oil in the bottle, but I previously seemed to have oil all over the top of the gearbox that was dripping out of the air filter. A tiny bit of oil seems to go a long way especially when whipped around with 60mph winds.

Dave
69S

nr325996 said:

There is oil coming out of the breather hose then it is dripping out the bottom of the air filter housing, does this mean im getting pressure in the crankcase ??? plkease help

Click to expand...

It normally means you filled the tank with too much oil.

maylar said:

It normally means you filled the tank with too much oil.

Click to expand...

+1

Two things lead to overfilling the tank:

1) you checked the oil level and topped off before running the bike. Most Nortons wet-sump to some degree, and letting it sit for a couple of weeks can lead to a quart or more seeping through the gears of the oil pump into the crank case. Either drain the sump and put that oil back in the tank, or start up the bike and let it warm up before checking the oil level. The pump will drain down the case in a few minutes.

2) You filled the tank past the lower mark on the dip stick. These dip sticks were made in a couple of different lengths, apparently, and bringing the oil to the top mark on a short stick will bring the oil level too close to the breather pipe at the top of the tank, especially if the oil is splashing around a bit from bike movement. A little trial and error will tell you how full is too full, but the bottom mark on the stick is a good starting point.