A10 oil out of breather

[limeyrob]

I thought I'd start a new thread with the correct title.
Breather now has pipe to rear plate and catch bottle and bike is going well, loads of compression and little smoke.  New rings have done about 250 miles, next job is oil change from 20-50 to straight 50.
Catch bottle means bike (and me) are now clean after a run.
Cork replaced, SRM oil pump and SRM relief valve.
BUT!!!
The 1" dia by 3" long bottle fills in about 10 miles so a 30 mile run would be about a cup full.
This afternoons job is to make a bigger catch bottle while I search for ideas.
Suggestions as to what's going on please.

[Superflash]

Surely to blow that much oil, it's over pressurising in the crank case?
I've seen examples of guys fitting a bunn type valve in the exhaust valve cover to help drop pressue. Could be worth a look?

[Ted_Flash]

I had this problem with my A10, and resorted to lots of attempted fixes including a catchpot.  Eventually I sorted it by fitting a set of IMD pistons/rings, with just a rub over with glass paper for the bore.  Although I didn't suffer smoking exhaust or oily plugs, the old rings must have been allowing the crankcase to be pressurised. A set of IMD pistons costs £125 and is a very worthwhile investment.

https://imdpistons.com/collections/bsa-pistons

[JulianS]

Similar breather discharge problem happened twice on my A10.

First was caused by a split oil seal on the SRM end feed conversion.

Second was caused by a partial obstruction in the internal return pipe in the oil tank.

[DAVE BRADY]

Hi,

I think that you mentioned that the engine is recently reassembled and not ridden much due to the oil issue.
If all is assembled properly there should be no oil coming out of the breather but perhaps some oil mist.  Whilst bedding in the rings some may escape but it should stop after a relatively low mileage.
You have a new SRM pump so any oil accumulating will be returned to the tank pretty quickly.
Check the compression to see if the rings are doing their job otherwise check everything on the timing side and in the sump again. Something must be amiss.

Dave.

[limeyrob]

Thanks, there's some good suggestions.  Its dripping oil rather than oil mist and while it does breath I don't think its excessive and compression is good but while the rings are new Hepolites I did not have bore as its plus 60 already.
That obstruction of the oil return is intersting. It has Norton style cartridge filter on the return and while there is a good return flow I do wonder if this is playing a role.
I have the Eddie Dow rocker covers and one has a boss for a breather, I could drill and tap that and see what effect it has, easy enough to put a blank in later.
What are your thoughts on SAE50?
I should add its 9:1 comp.
Thanks

[scifi]

The usual running-in process is to use straight non detergent sae50 first, Then use the friction modified 20/50 after the running-in has been done.

[DAVE BRADY]

Hi,

The filter will be fine but ideally a running in oil should be used to assist the bedding in of shells, bush and rings.  Discard this oil after 50 miles and then use what is left of 5l of the bedding in oil with a detergent 20/50.  Change again for 20/50 after another 100 to 150 miles. Change again and now use the detergent 20/50.  This oil will take all the fine particles to the filter rather than allow them to be caught in the sludge trap.
I think the filter is designed for 20/50 oil rather than a straight 50.  Whilst allowing oil through, hence a return to the tank, the thicker oil may be backing up in the sump.
20/50 oil is designed for plain bearings like bushes and shells.
What oil do you have in it and did you have the bore lightly honed for the new rings?

Dave.

[iansoady]

Although a good filter should cope with straight 50, the filter is a good thought. Why not bypass it temporarily so you can eliminate it as a possibility?

[limeyrob]

Lots to think about there.  I'll report back.