Hi Peter, If the smoke is oil related its also possible it could be comming from above,through the valve guides perhaps? especially if the oil drain from the head back down to the sump is restricted in some way.I have no knowledge of the B31 but its just an idea and may be worth a look before you replace the pump.Mick
email (option): sally_jones@btinternet.com
Hi Peter, If the oil return from the head is blocked the valve spring pocket(s) will flood and oil will be drawn down the guide(s) resulting in a lot of smoke. It is not a common problem but possible..a B33 engine I repaired for someone once had exactly this problem , the drillings in the head being completely blocked with blasting grit as it turned out.
Another possibility is that the anti drain valve in the timing cover or the one in the base plate of the oilpump are not seating correctly. If the pump gears are worn and either of these valves are not functioning it is entirely possible for a measurable amount of the oil from the tank to drop into the sump overnight.
Also if the ball in the pump base plate is stuck on its seat (the reverse problem) oil will not be scavenged from the crankcase. In either scenario the excess oil is thrown up by the crank and overwhelms the oil scraper ring..and you get smoke.
A 'spit and bubble' return at the tank is normal if everything is functioning correctly as the engine is 'dry sump' and the return side of the pump, which has a greater capacity than the feed side, will empty the cases and then not have much to pump.
Conversely though, it also wont have much to pump if there is an oil pick up or pumping problem.
If it continues to smoke, take out the crankcase drain plug. If nothing, or very little, comes out that will discount pick up, pumping or drain valve problems, all of which would produce excess oil in the crankcase. Possible blockage of the oil return from the head, or perhaps a scraper ring broken during assembly would then bear further examination..
To check the anti drain valves empty any oil from the crankcase in the evening and check again to see what you have the following day. If it is dropping oil overnight it will take more than a 'quick run up' in the shed to clear it..It is very, very rare for a BSA pump not to do the job OK..in all the years I have owned BSAs and rebuilt them for myself and others it has only occured once..Ian
email (option): ian@wright52.plus.com
Hi Eric..Both anti drain valves are 'downstream' from the oil pump..So oil comes from the oil tank to the pump and then to the timing cover anti drain valve before going on to the cams, big end etc.
This valve is there because oil can drain past the pump gears and into the crankcases via the 'feed' oilways.
There is also another route to the crankcase though..that is past the oil pump gears and down the pipe that picks up oil from the sump when the engine is running and then into the crankcase.
That is why the ball is fitted to the pick up tube. When the engine is stationary the oil that drains through the pump and the weight of the ball itself 'seat' the ball into the bottom of the tube preventing, or at least limiting leakage.
The ball in the timing cover is held in place by a spring and is lifted by the oil pressure when the engine is started and the oil pump begins to pump.(lift occurs at approx. 7 psi)
The ball in the pick up tube is not spring loaded as it is moved of its seat by pump suction, not pump pressure, which is far less effective.
The timing cover ball can be reseated into the case by removing the timing cover fitting and spring and placing a punch against the back of the (1/4" dia) ball and giving the punch a light but sharp tap with a hammer.
The ball in the pick up tube (which is part of the pump base plate) is held in place and has its total movement restricted by a very small wire 'pin' that goes through the tube just above the ball.
To inspect the ball and its seat in the tube the oil pump must be removed from the engine and the base plate and pin removed. The ball will then fall out of the tube when inverted.
A build up of dirt, corrosion or damage to the pump tube seat and/or corrosion on the ball can prevent the ball sealing correctly.
Personally I wouldn't consider fitting an aftermarket in line valve..They are not specifically manufactured for the BSA engine and rely on pump suction to lift a spring loaded ball...Pump pressure and suction (and thus the capability to lift the ball) varies from pump to pump depending on the degree of wear in the gears and housing and also a build up of contamination from the oil over time could affect the operation of the valve itself...any operational failure in the feed line is going to mean a major engine lubrication failure..and it does happen...I personally know of two engines that have failed as a direct result of the fitting of one of these anti drain valves.
No doubt there are people who haven't had problems and will be quick to report that fact...for myself I will never fit anything I think could potentially compromise the oil feed..With the fitting of inline valves (which the engine already has) it is also the case that the symptoms are being treated, not the cause..a little work on the existing valves (including the fitting of a new spring to the timing cover valve) will reduce leakage to a level where it is not problematical...Ian
email (option): ian@wright52.plus.com