Crankcase breather blowing oil

I had a similar problem with my 1972 Commando. This was diagnosed as worn bores. So I had a cylinder rebore and new pistons. The previous oiling of the rear tyre disappeared completely.

However, I still get a cupful of gunge in my 250ml catch bottle that needs to be emptied every 400 miles. This is a mix of water, oil and the white Mayo that used to coat the inside of the oil cap. It might be caused by the cheap, basic 20/50 oil I used during the bedding in process.

A more experienced owner than me has suggested that if the problem persists when using a better quality oil then a service of the oil pump might help.

I had better add here that prior to my tyre oiling days, the line to my catch bottle used to go straight back to the carb as part of an emission recirculation system.

Previously ernie_olivo wrote:

Previously phil_hannam wrote:

I had a similar problem with my 1972 Commando. This was diagnosed as worn bores. So I had a cylinder rebore and new pistons. The previous oiling of the rear tyre disappeared completely.

However, I still get a cupful of gunge in my 250ml catch bottle that needs to be emptied every 400 miles. This is a mix of water, oil and the white Mayo that used to coat the inside of the oil cap. It might be caused by the cheap, basic 20/50 oil I used during the bedding in process.

A more experienced owner than me has suggested that if the problem persists when using a better quality oil then a service of the oil pump might help.

I had better add here that prior to my tyre oiling days, the line to my catch bottle used to go straight back to the carb as part of an emission recirculation system.

Hi Phil

I've had a fresh re-bore, piston, and rings. I'm using 20/50 oil. I don't see the "mayo", just regular oil. The amount blown is somewhat more than I'd like to re-direct to the ass-end of the rear fender like the setup on my Triumph.

How many miles since the fresh rebore? Do you have any white smoke on startup or while running?

How many miles since the fresh rebore? Do you have any white smoke on startup or while running?

Have covered 800 miles since rebuild including visiting the Brixham Rally. Pistons have Chrome top rings which apparently take ages to bed in. No white smoke on start either from burning oil or condensation. Compression is far better than pre-rebore but no need to stand on kickstart to turn crank. Will change the oil for Silkolene 20/50 asap.

Previously ernie_olivo wrote:

My sincere thanks and apologies. How often do we older gits screw up?

i had reversed the crankcase vent line and the oil tank vent line where they enter the tank, so of course it was blowing oil.

A quick fix and a much longer clean-up.

humbly,

e

your problem maybe in the crankcase large filter plug been partly blocked and the pump is not scavenging right, empty your oil tank , and remove oil pipes and remove crankcase plug , and with a air line blow down the oil ways by the pump back into the crankcases then remove the oil pump and give it a clean in white spirit , the blow down the oil way from the pump end with the pump out of the way, see if there is any bits of crap in there, the this is a good time to clean out the oil tank at the same time, so once you then cleaned all the oil-ways and oil tank and oil pump , then reassemble it all and fill with fresh oil , and see if its still doing the same thing, , but it should not,

good luck with it all anyway, yours anna j

Anna, I think you will find that Ernie has already solved the problem.

Previously Gordon Johnston wrote:

Anna, I think you will find that Ernie has already solved the problem.

Well thanks for that Gordon where would we be with out you around its is what makes this club, good communication between

us Norton lovers

yours Anna J

Previously ernie_olivo wrote:

My sincere thanks and apologies. How often do we older gits screw up?

i had reversed the crankcase vent line and the oil tank vent line where they enter the tank, so of course it was blowing oil.

A quick fix and a much longer clean-up.

humbly,

e

Hi You resolved the problem before i could respond but i had the same strange loss of oil/mayo and the solution was the same. I lose very little now.

Mark.

Hi Ernie,

Enjoy the trip and send pictures.

Regards

Tony