sludge trap clearing

[Greybeard]

I’m in Wellington Shropshire. No, not Telford, it’s near Shrewsbury!!!

On one of the BSAOC weekends, we rode to a microbrewery in a pub in Wellington. Do you know that one?

[Minto]

That will be the Pheasant in town (market street I think) Unfortunately I’d heard recently that they no longer brew there anymore.

[a10rgs]

Minto,

if you have split your chrankcase it is a good idea the remove the small grub screw of the nrv and clean it and the oilways too! Use a new ball (1/4") when refitting the screw and spring!

Cheers 

[Greybeard]

if you have split your crankcase it is a good idea the remove the small grub screw of the nrv and clean it and the oilways too! Use a new ball (1/4") when refitting the screw and spring!

Edited: This non-return valve, (nrv) is designed to stop anti wet sumping, so a good idea to service it when the cases are apart. Change the spring as well as the ball.

[BSA_54A10]

Every BSA owner should have a packet of NRV springs.
Every time the NRV is exposed during engine work, the spring should be replaced.
A spring is only a spring because of the heat treatment it gets.
Every second your engine is running, hot oil passes over the spring slowly softening it.
The older the engine, the more important this becomes
What  most fail to understand is the ball only moves a few thou and the spring has to be strong enough to make an oil tight seal ( we hope ) yet weak enough to open under the very small pressure difference caused by the pump pumping.
Every time you "seat" the ball, usually with a 10lb hammer you move the seat in a few thou so the spring force gets weaker as it is now extended a few thou further in the fully closed position .
 

[Minto]

I haven't got as far as dismantling yet, but thanks for the heads up. I am new to A10 ownership and all of the maintenance that goes with it so all advice is gratefully received.
Where about is this NRV? Like I say, new to this!!
GB, you say it's there to prevent "anti wet sumping"? Bit confused, is it an anti wet sumping valve or is it to prevent wet sumping? Sorry, could be me being not used to terminology and BSA speak.
Cheers
Jase

[Minto]

Could also be one too many glasses of rum at early o'clock!!!

[terryg]

The 'nrv' (ball and spring) is in the timing side crankcase half, directly behind the oil pump in the feed line. So it is only accessible by splitting the crankcases in the A7/A10 design.
Wet sumping is the result of a poorly sealing 'nrv' and gravity working to relocate the oil in the high tank to the low sump by leakage through the oil pump.
You'll find many forum threads discussing owner modifications to overcome the need to separate the crankcases to maintain the 'nrv'. You'll also find mention of 'anti wet sumping valves', which are non-standard additional ball and spring assemblies fitted in the oil feed line where it enters the crankcase. In this case the ball must be sucked off its seat by the oil pump action, in contrast to the standard 'nrv'. I would not recommend this approach as its reliability is questionable and, even when working as intended, the oil flow is reduced.

[Swarfcut]

Minto.  Years ago we all went by the book and observed the BSA recommendation to leave that ball valve well alone. In normal regular daily use the small amount of oil draining down overnight was easily cleared on start up. The problem comes with standing unused for longer periods.  Oil accumulates in the engine crankcase, this is termed "wet sumping". The oil pump is really two pumps, side by side. The scavenge side has greater capacity , so returns oil to the tank to leave a "dry sump".

 Terryg is right, the external aftermarket valves to prevent this wet sumping always have a degree of uncertainty about them.

 So, if and when the time comes, it is worth checking that all is well. It's just a ball on a spring, but probably a bit gummed up.

 The valve is in the oilway between the oil pump output and the timing bush. When the pump is taken off, you can feel the ball with a matchstick deep in the oilway. It should move easily and return to its seat. The spring has to hold the ball valve closed at rest, but open under oil pressure to allow oil flow to the bush and the rest of the engine. In a way it impedes flow, so some people remove it and put an external tap or valve in the feed to the pump, again fraught if you forget to turn on the tap or the external valve sticks, as outlined above.

 So, your options are to  just clean it with a good blast of carb cleaner, or dismantle and replace ball and spring. The only access is from inside the crankcase, carefully drill away the locking dimples and unscrew the grub screw, spring and ball will lift out. The grub screw is under full oil pressure, with the engine running, so ensure an oil tight seal on replacement, a good dose of Loctite is usually used, pessimists also reinstate the locking dimples.

 This also explains the popularity of nice sump plates with a drain plug...very convenient and a lot less hassle.

 Save some cash at Stafford, the Forum has its own rather stylish and exclusive T Shirt......

 Swarfy.

[Greybeard]

GB, you say it's there to prevent "anti wet sumping"? Bit confused, is it an anti wet sumping valve or is it to prevent wet sumping?

Soz, I've just edited my post to make more sense