BSA B31: Strange oil leak from Timing case

[briancairns]

Bottom right hand side? are we talking were the pressure release valve is? maybe a photo would help not sure were you mean exactly, however there is or should be a hole in the gasket for the pressure release, is this covered up

Hi, there is definitely a whole in gasket for non-return valve, it is the correct gasket and all holes are as they should be. I aslo replaced the ball bearing and spring.
I have 'scribbled' a red line on attached photo , where the oil leaks from, that is oil drips between cover and body of timing case However only leaks when engine is running.

Thanks
Brian

[briancairns]

Bottom right hand side? are we talking were the pressure release valve is? maybe a photo would help not sure were you mean exactly, however there is or should be a hole in the gasket for the pressure release, is this covered up

My timing cover was cracked next to the non return valve, probably caused by the screw being over tightened. Is there any chance that this is the cause of the problem?

I fixed it with JB Weld, after undercutting the crack.

Definitely no cracks in casing.

Thanks

Brian

[paulm]

sound quite possible

[briancairns]

Unless I have misunderstood your problem, you may be looking for a problem that doesn't exist.
Now that you have solved the quill problem, I would suggest you firstly carry out a Cylinder Leakage Test. You can find details on the Internet, although mostly USA.
Kits are available, but they are rather expensive, as you'll probably only use it once. I made up my own kit, but it ended up costing the same.
This will tell you if you have excessive crankcase pressure and more.
I had the same problem on a Vintage BSA, with sealant being pushed out of the joint by pressure (of which there will always be some). I tries all sorts of sealants, but having discovered the engine did not have excessive crankcase pressure, I used Loctite 518 and the problem was solved. I keep it in the freezer, disguised as a cucumber.
Do check the mating surfaces where it's leaking carefully with a straight edge. Perhaps you could loosely assemble the cover without gasket, and check the gap all the way round with a thin feeler gauge?

Did a compression test and got 155 psi...should I still do a leakage test? still waiting on my friend to lend me his kit.
cheers
Brian

[Steve.S]

Well, Brian, 150 lbf/sq.in. is good and would tend to indicate that you may not have too much pressure passing by the rings. It all depends on how concerned you are about excessive crankcase pressure. 'IF' your breather is blocked, then the pulsing will be more pronounced, but even if it is clear, I imagine there would be some normal pulsing as the piston descends.
My feeling is that assuming the mating surfaces are 100% and with new thickish gasket, the crankcase pressure would have to be considerable to force a leak, and I don't think it is. Are you certain it's coming from the joint? 
If so, I would try the Loctite product (leave it overnight before you start the engine). I wonder if you might fit the screws without the case, to ensure they're going in far enough to clamp the case? Someone might have fitted longer screws?
If you're convinced there's too much pressure, then try the Cylinder Leakage Test.
However, be warned that when you apply air pressure to the cylinder with the piston at TDC and both valves closed, as you further open the regulator, it will become increasingly difficult to hold the engine at TDC (Putting the bike in gear with the brake on certainly won't work.) If you get up to a high pressure and your jamming method lets go, it could be catastrophic.

[Steve.S]

I've just had another thought. Is the screw hole adjacent to the leak in communication with the timing chest? If so, you may want to fit that screw with a sealant such as Hylotite Red, with, maybe a fibre washer.

[briancairns]

I've just had another thought. Is the screw hole adjacent to the leak in communication with the timing chest? If so, you may want to fit that screw with a sealant such as Hylotite Red, with, maybe a fibre washer.

I used Granville Clear Gasket Sealant around the area which leaks, so will do a test run later. If leaks again I will look at fitting a fibre washer etc to screw adjacent to leak. Don't think I will do cylinder compression leakage test. Also I think I will blow compressed air up the oil tank breather tube to ensure there is no blockage there.
cheers
Brian

[briancairns]

I've just had another thought. Is the screw hole adjacent to the leak in communication with the timing chest? If so, you may want to fit that screw with a sealant such as Hylotite Red, with, maybe a fibre washer.

I used Granville Clear Gasket Sealant around the area which leaks, so will do a test run later. If leaks again I will look at fitting a fibre washer etc to screw adjacent to leak. Don't think I will do cylinder compression leakage test. Also I think I will blow compressed air up the oil tank breather tube to ensure there is no blockage there.
cheers
Brian

ok, I blew compressed air up the oil tank breather, heard a pop, air flowing freely. Took bike out for 10 mile test run, slight oil weep from timing case and the odd spit of oil from timing case breather. I think that's the best I'm going to get.
thanks all for the marvellous advice.
Brian

[Derek996]

Just a thought. Exactly where the leak is showing there is an alloy plug in the timing cover sealing a drilling for the oil gallery to the crank feed. There is a (very) small possibility that it is leaking from the plug.

[briancairns]

Just a thought. Exactly where the leak is showing there is an alloy plug in the timing cover sealing a drilling for the oil gallery to the crank feed. There is a (very) small possibility that it is leaking from the plug.

Is the alloy plug in the area marked with a red circle ?

[Derek996]

No, it's on the outside of the casing directly below the the oilway that runs from the small hole in the cover to the crank feed quill.

[briancairns]

Not sure my casing has what your are referring  to?

Cheers

Brian

[Ian C]

I believe Derek is refering to the alloy plug circled in red which was fitted after BSA machined the oilway to the quill.

[briancairns]

I believe Derek is refering to the alloy plug circled in red which was fitted after BSA machined the oilway to the quill.

No , My casing definitely does not have that...1954 BSA plunger

[Derek996]

I believe Derek is refering to the alloy plug circled in red which was fitted after BSA machined the oilway to the quill.

No , My casing definitely does not have that...1954 BSA plunger

They all have it Brian, even my 1948 B32. It's a necessary part of the manufacturing process but if your's is more or less invisible it's probably not the source of the leak.