BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: cee-b on 14 November, 2017, 19:38:17

Title: C15T crankcase breather oil leak - but only some times!
Post by: cee-b on 14 November, 2017, 19:38:17
I know that the subject of oil leaks has been covered countless times and apologise for raising it again. However, I can't find a previous answer for this particular set of circumstances.

When I leave the bike parked, it leaks oil from the RH side of the engine (nothing unusual about that, I know).

Removing the outer timing cover shows oil pooling and weeping out through the join; it actually drips from the rear RH stud of the sump, but this is only because it tracked to that low point.

The oil is entering that cover through the small breather hole low down in the gearbox inner cover - presumably this is the timed crankcase breather?

On some occasions this leak is barely more than a drip, on others however, it makes a fairly massive puddle. I can only surmise that the difference is due to whether the breather is timed open or not.

So, I have a two-part request.

1. Can anyone suggest a method of curing the leak?
2. If not, is there a method of determining whether the breather is open or closed without waiting for the puddle to form?

Any insights will be gratefully received.

 
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: om15 on 15 November, 2017, 11:50:07
I have a (relatively) oil tight engine, however occasionally the engine used to wet sump and dump the contents of the system over the floor when parked up.
As in general the engine did not leak I was loath to strip it, I saw that many AJS and Matchless bikes had a tap in the oil feed line from the tank, so I fitted a small tap (gas tap with 3/16" internal bore). When the bike is parked up for long periods I simply switch it off, - then remember to switch it on.
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: JulianS on 15 November, 2017, 12:43:50
The timed breather is on the camshaft not low down.
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: JulianS on 15 November, 2017, 14:36:02
The breather outlet is either a half moon cutout at rear of outer timing cover or a tube adjacent ro the external clutch lever, depanding on the year of your engine.

If oil is coming out of the outlet you may have  excess oil in the sump due to wet sumping and/or there is wear in bore and/or rings and or valve stems and/or valve guides.
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: cee-b on 15 November, 2017, 21:58:50
I have a (relatively) oil tight engine, however occasionally the engine used to wet sump and dump the contents of the system over the floor when parked up.
As in general the engine did not leak I was loath to strip it, I saw that many AJS and Matchless bikes had a tap in the oil feed line from the tank, so I fitted a small tap (gas tap with 3/16" internal bore). When the bike is parked up for long periods I simply switch it off, - then remember to switch it on.

Thanks, but I am reluctant to put anything in the system that could lead to oil starvation. I only have to think of the number of times I've forgotten to turn fuel on or off to know that would not end well.
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: cee-b on 15 November, 2017, 22:08:32
The breather outlet is either a half moon cutout at rear of outer timing cover or a tube adjacent ro the external clutch lever, depanding on the year of your engine.

If oil is coming out of the outlet you may have  excess oil in the sump due to wet sumping and/or there is wear in bore and/or rings and or valve stems and/or valve guides.


Thanks for your response Julian; good information as always. I'll see if I can find the crankcase breather outlet in the locations you mentioned

I think you are almost certainly correct that it is excess oil in the sump. I'm now wondering what the small 'pin hole' through the gearbox inner cover is? That is where it is leaking from.

I'll take a pic tomorrow and post it on here.
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: JulianS on 15 November, 2017, 22:13:09
The theory is that oil mist which condensates and accumulates in the oter timing case drains back into the crankcase via that tiny hole.

If you remove the outer cover you will seee the breather port by the cam bush.
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: cee-b on 16 November, 2017, 12:14:02
OK, that makes sense - thanks.

The real problem, then, is wet sumping causing oil to come out of the oil mist (inward) drain.

The difference in how much oil comes out is most likely due to slight differences in the angle it is parked at and length of time it is left.

Thanks again Julian 
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: cee-b on 16 November, 2017, 12:17:27
Just a quick thought:

As the oil mist drain is currently creating more of a problem than it is solving; is there any reason not to temporarily block that drain hole until I can solve the wet sumping problem??
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: JulianS on 17 November, 2017, 11:20:41
I dont think that little hole is the problem, excess oil in the sump will either pass the rings and burn giving a smoking exhaust or will be pushed out of the breather - photo is how BSA describe the breather
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: cee-b on 17 November, 2017, 16:47:02
I dont think that little hole is the problem, excess oil in the sump will either pass the rings and burn giving a smoking exhaust or will be pushed out of the breather - photo is how BSA describe the breather

Thanks Julian, I had located the breather from your previous post. I'm afraid it was a red herring that I had introduced in error.

The oil is definitely coming from the small 'pin hole' drain near the bottom of the cover - I can watch it weeping out and dripping down the casing to the low point (sump bolt, RH rear).

It is only a small drip but, over time, it makes quite a big puddle.

I have taken a pic but it is too many KBs to be accepted as an attachment; I'll try and find some other way of posting it.
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: JulianS on 17 November, 2017, 16:50:25
If you have windows 10 you should have the program "Paint" which will resize a photo.

If you drain the sump do you get much oil? I did ot think the hole was low enough to allow a leak.If it drips from such a small hole there must be a lot of oil in there.
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: cee-b on 17 November, 2017, 17:05:21
Trying as a PDF

That seems to work. I haven't drained the sump since identifying the leak; I'll give it a go now
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: cee-b on 17 November, 2017, 17:25:51
It was holding 200ml. Not the driest of dry sumps!
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: Mike Farmer on 18 November, 2017, 13:57:47
Hi.

I had a wet sumping problem on my A50. I put in any anti wet sumping valve. 35 ish and a fairly easy job.  No more wet sumping.

I was against the idea to start with, but when I mentioned it here, several guys gave me positive results so I went for it.

It easy to see that it is working by watching the return pipe in the tank.

Worth a thought???

Mike
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: JulianS on 18 November, 2017, 14:36:49
That is a lot for a dry sump engine. My A10 drains about 100 ml after standing overnight.

I always suspect the oil pump to crankcase joint and the condition of the pump. If it is worn then no hope of stopping it without soe external valve.

In the past I have used a valve like Mike to good effect. You just need to make sure the oil pipe both sides is charged with oil and there is no airlock in the feed side, which will stop oil feed.

Dot like taps too much risk of forgetting to turn them back on and the risk of an airlock in the system .
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: cee-b on 18 November, 2017, 16:57:19
The oil pump is a recently replaced recon item so I can't really get improvement there.

I have noticed that the level in the scavenge pipe (I have clear pipes) drops by around 5"over the course of a couple of days, so it is certainly leaking back through the scavenge side of the pump.

I'll put an NRV in the scavenge line to prevent that, but am not convinced that putting any restriction in the supply line is a great idea. I'll just buy Mrs B a replacement for the baking tray I've just nicked out of her range to park under the sump - problem solved (ish)  ::)

Thanks for all the help & advice guys.
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: JulianS on 18 November, 2017, 18:57:32
That will not solve your problem. The oil in the return is aerated and will settle and that pipe cannot draw oil from the tank.

Wet sumping is either a poor scavenge side of pump/blockage in return  and/or leaking down the feed side either through the pump joints or gears or the non return ball valve in the system - theball and spring reatined by the grub screw you se by the main bearing bush inside thecrankcase..

Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: cee-b on 18 November, 2017, 21:11:03
Yes I think you're right Julian. The ball and spring could well do with looking at/renewing, but that is going to have to wait until next time I have the engine apart; I'm not going to go into it just for that.
Title: Re: C15T crankcase breather oil leak - but only some times!
Post by: ANDY HIGHAM on 18 November, 2017, 21:34:11
Hi.

I had a wet sumping problem on my A50. I put in any anti wet sumping valve. 35 ish and a fairly easy job.  No more wet sumping.

I was against the idea to start with, but when I mentioned it here, several guys gave me positive results so I went for it.

It easy to see that it is working by watching the return pipe in the tank.

Worth a thought???

The A50 and A65 have an anti wet sumping valve from the factory. It is the ball and spring behind the oil pump. The valves that fit between the tank and the engine could cause oil starvation, pumps do not like to suck

Mike