BSA wet sumping

I have it in my notes from way back that the BSA wet sumps if left for 2 months or more.
Now that I will be riding the bike quite a bit that should be a non issue.
BSA twins have a ball and spring affair to help prevent wet sumping. It's not a perfect arrangement from what I have read. It can be ineffective at preventing wetsumping and, very infrequently, it can stop the flow of oil back to the tank.
This one seems to be working well.
As a test I drained the sump for 1 day then put a clean empty container under the open sump drain for 4 days.
Total accumulation in 4 days is about 6 or 8 drops of oil!

The other thing that I like about this bike is the enclosed chain. The gearbox seal weeps a tiny bit and that ends up on the chain. Because the chain is auto lubed and is not exposed to grit, it looks like it will last a very long time.
Also, there is no lube flinging onto the wheel rim and other places.

I once observed an acquaintance with a BSA Spitfire start it up after some time standing. He was about to head off for a ride when I shputed and pointed to ground under the bike where latte-esque puddle of oil was rapidly collecting. Puzzled by this he handed me the workshop manual and he buggered off on an urgent errand. Flipping through the pages haphazardly I came to a section about the anti wet sump spring valve and how if not operating coorectly oil will be forced out of the engine. Cannot recall the details, but fix had to do with removing the valve and cleaning etc.

Although its a ball and spring type, it is a much more socially acceptable valve than any of the external ones.
It is on the pressure side, nonetheless it can jam.
BSA put it there so it must be OK!
I'm glad this one is working so well, at least for the anti-wetsump effect.
According to my reading, if you do need to replace the ball or spring then the cases must be split, not exactly a user friendly arrangement!

Glen

worntorn said:

Although its a ball and spring type, it is a much more socially acceptable valve than any of the external ones.
It is on the pressure side, nonetheless it can jam.
BSA put it there so it must be OK!
I'm glad this one is working so well, at least for the anti-wetsump effect.
According to my reading, if you do need to replace the ball or spring then the cases must be split, not exactly a user friendly arrangement!

Glen

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The spitfire book deswcribed how to clear it up, which we proceeded to do without a lot of effort in his driveway...some must be a different setup in that bike. He let me ride it up/down the lane....I got a little freaked out though...had never had a bike with a steering damper adjuster and it must have been pretty tight...could barely steer the infernal contraption.

Yes, the A65 valve is different from the the A7/A10 type. Some A10/A7 owners convert their machines to the A65 type anti drain arrangement.

Glen

Tornado said:

The spitfire book deswcribed how to clear it up, which we proceeded to do without a lot of effort in his driveway...some must be a different setup in that bike. He let me ride it up/down the lane....I got a little freaked out though...had never had a bike with a steering damper adjuster and it must have been pretty tight...could barely steer the infernal contraption.

Click to expand...

I'd never condone it now but when you are young and stupid the temptation to screw your mates steering damper down really tight when he's not looking was quite overwhelming!
A friction steering damper had no place on an a65 except if you were lugging a sidecar

worntorn said:

BSA twins have a ball and spring affair to help prevent wet sumping. It's not a perfect arrangement from what I have read. It can be ineffective at preventing wetsumping and, very infrequently, it can stop the flow of oil back to the tank.

Click to expand...

It’s not the spring loaded ball valve downstream of the pump that stops the scavenge flow.

There’s a captive loose ball in the end of the scavenge pipe in the bottom of the crankcase.

It’s notorious for sticking shut when well-meaning owners fit a magnetic drain plug. Or it can sometimes stick for no great reason.

That makes sense.
I have read of the occasional problem with the spring and ball as well. Most often the problem is that it stops working as an anti wet sump valve. In one case though it did impede oil flow to bearings etc. and wrecked an engine. In that case it was decided that an incorrect spring had been fitted.

This SR lubrication system seems to be working well, as near as I can tell. There is a strong flow back to the tank and the built in anti wet sump feature is working very well. Hopefully there is adequate lube making its way through the engine, especially to that timing side bush that can be problematic.
I have considered adding a Norton type spin on oil filter as many have done with A7s & A10s. That might be a project for next winter. For now I'll just change the oil fairly often.
I'm planning to ride the bike quite a bit this year, likely on local rides that are 100 miles or less and 60 mph or less.
From recall it started to get buzzy at 65 mph or so, but was quite smooth up to 60mph.

Glen