BSA B31: Strange oil leak from Timing case

[Derek996]

In view of the quill being loose, I'd investigate why this has occurred. Is it a case of there not being enough concentric clearance between quill and crank?
To Brian, Have you tried placing the quill into the end of the crank and turning it?

Might be an idea to check the truth of the crankshaft as this could a reason why the quill has come loose.

[briancairns]

In view of the quill being loose, I'd investigate why this has occurred. Is it a case of there not being enough concentric clearance between quill and crank?
To Brian, Have you tried placing the quill into the end of the crank and turning it?

Might be an idea to check the truth of the crankshaft as this could a reason why the quill has come loose.

To be honest I have no idea to check the truth of the crankshaft?

Thanks
Brian

[Derek996]

A quick method to get an idea is to use one of the timing cover screw holes to attach a pointer. Line it up so it is a fraction of a millimetre from touching the crank at the side of the tip where the quill fits. When you rotate the crank and eyeball the gap the distance should remain the same, if not there is a bend on the shaft.
To get a more accurate measure you would need to do the same with a dial guage with the tip of the guage just touching the shaft. Any run out will show by the variation on the needle. Maybe up to about .002" to .004" is probably acceptable.

[briancairns]

A quick method to get an idea is to use one of the timing cover screw holes to attach a pointer. Line it up so it is a fraction of a millimetre from touching the crank at the side of the tip where the quill fits. When you rotate the crank and eyeball the gap the distance should remain the same, if not there is a bend on the shaft.
To get a more accurate measure you would need to do the same with a dial guage with the tip of the guage just touching the shaft. Any run out will show by the variation on the needle. Maybe up to about .002" to .004" is probably acceptable.

Great and thanks
Brian

[neil1964]

Intrigued to know if this has been resolved?

[briancairns]

Intrigued to know if this has been resolved?

Got the parts on Wednesday evening then was away a few days motorcycling, only back last night, I aim to get job done tomorrow and will let you know.
cheers
Brian

[briancairns]

Intrigued to know if this has been resolved?

Got the parts on Wednesday evening then was away a few days motorcycling, only back last night, I aim to get job done tomorrow and will let you know.
cheers
Brian

Hi
I am afraid after test run oil is still leaking from bottom right hand corner of timing case cover and now also a bit from the breather:

work done:

Cleaned breather valve
cleaned casing cover and screw holes thoroughly
New casing cover bolts
New big end oil feedquill ( which still wasn't overly tight) and used locktite 648 to lock quill in appropriate position
new camshaft oil seals
Checked trueness of crankshaft ( as best I could)
Tested oil flow back to oil tank and also feeding the head
New gasket using WellSeal jointing compound.

I only went 2 miles and stopped to check but oil started to drip out of timing case and a few drops from breather.

Think I will now seal bottom right hand corner of timing cover and gasket with CT1 sealant or black instant gasket........all out of ideas

Thanks all

Brian

[neil1964]

I presume that you know it is not wet sumping and the breather disc is moving freely?
Oil from the breather sounds like excess crankcase pressure being part of the issue?

[briancairns]

I presume that you know it is not wet sumping and the breather disc is moving freely?
Oil from the breather sounds like excess crankcase pressure being part of the issue?

Definitely not wet sumping as I also took sump plate off to clean filter all ok. Yes breather is moving freely after I cleaned it. I have no idea why there seems to be excess crankcase pressure. Bike was going fine until I took magneto off to get a bearing changed. Put it together, set timing, starts 1st kick every time . I ended putting granville clear sealant around gasket etc and will test ride again tomorrow but concerned that there definitely seems to be excess crankcase pressure.
Thanks
Brian

[paulm]

checking the breather with a air line is to powerful the breather works on low pressure, a airline need to be turned right down to do this, i tend to blow and suck, now if there is crankcase pressure there are only two small drain holes from the timing cover chamber to the main crank case were it scavenges , if pressure builds up in the timing cover chamber it will raise its oil level as it will not drain quick enough and come out the breather, this level can be raised for numerous reasons worn bores, guides air leaks quill leaking excessively, the issue is caused by the timing case filling up, you need to find out why, i find these engine run well till you disturb them and this happens, try a compression check for starters, these breathers are useless and take very little not to work so start there and move on

[briancairns]

checking the breather with a air line is to powerful the breather works on low pressure, a airline need to be turned right down to do this, i tend to blow and suck, now if there is crankcase pressure there are only two small drain holes from the timing cover chamber to the main crank case were it scavenges , if pressure builds up in the timing cover chamber it will raise its oil level as it will not drain quick enough and come out the breather, this level can be raised for numerous reasons worn bores, guides air leaks quill leaking excessively, the issue is caused by the timing case filling up, you need to find out why, i find these engine run well till you disturb them and this happens, try a compression check for starters, these breathers are useless and take very little not to work so start there and move on

I also took breather of the casing cleaned in petrol, disc flapping no problem, did the blow and suck thing, no problems. I replaced quill as one in bike was far to loose and spinning, the new quill although tighter , could still be spun by hand so used loctite 648 to fix in correct position ( this loctite is used to keep bearings in place etc). Will try compression test . I blew compressed air through all passages in timing case cover, no issues.The breather only blew out a very small amount of oil, the main leak was from bottom right hand side of cover.
cheers
Brian

[Steve.S]

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?

[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?

Thanks for your advice, a friend has a cylinder leakage test kit ( I think!) so hopefully will be able to check soon. Tried the straight edge across mating services but didn't detect any troughs etc but will try the feeler gauge technique.
cheers
Brian

[paulm]

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

[Rog1]

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.