Just sitting here, watching the rain, and got to thinking about my B40 (what occupied my mind before I took up this hobby?!) Anyway, having been talking oily things on this forum recently, I got to wondering how people check their engine oil level, and how important - or not - is it to have just the correct amount of oil in the bike. I know some tanks have a level line painted on the outside, but that can obviously only serve as a rough guide for peering down the hole. I guess a peep like that is good enough. Some bikes might have a dipstick as part of the filler cap. What I did was, when I had changed the oil, so I knew the right amount was in, I slid a steel rule down the filler hole, the lip of which is at an angle rather than vertical, until I could see it just touched the surface, took a reading at the lip, and made a note if it. But I had already primed the sump with 1/4, or was it 1/2, a pint. How much will be in the sump after a run, I'm not sure. Another factor of course is some bikes will wet sump, so if the bike is stood for a while before the oil is checked then the reading could be a long way off - it might appear to be low on oil when really it had just drained down into the sump. You could in that case start the bike and run it to get the oil out of the sump before measuring again, but if the low reading were true then that might not be a good idea?Anyway, easy ways to check the oil level? I guess you could make a dipstick of some kind, maybe with a top which fitted snugly on the (angled) lip. There might be some blindingly obvious way of doing this which hasn't dawned on me, and when somebody patiently points it out will make me feel a proper chump. Any thoughts? Phil
The best time to check the engine oil level is after a reasonable run out. Not only is the oil at its largest volume (fully expanded with the heat) but the sump should be empty of oil.
Hi Phil,
This might help:
Best wishes...
Quote from: AWJDThumper on 08 Jul, 2020, 10:00
The best time to check the engine oil level is after a reasonable run out. Not only is the oil at its largest volume (fully expanded with the heat) but the sump should be empty of oil.
So if, after a run, there is no oil in the sump, as you say, AWJDThumper, and if there is no wet-sumping, then that suggests the sump can be empty when we next start the bike. If that is true, then why do we prime the sump when we change the oil? I have a tap to prevent wet-sumping, but when I change the oil I remove the sump plate and there is oil in there - I guess about half a cupful or maybe a cupful. Phil
Oil will drain into the sump from the rocker box and engine internal surfaces.
If I drain my A10 sump after a run about 100cc of oil eventualy comes out. That is not wet sumping because no mre comes out if sump cover left off over night.
The thing to realise is that, when the engine is running, there is always oil distributed around the engine on components and surfaces that is trying to drain back to the sump. As Julian says, this is about 100 cc on a BSA single. This is not a problem provided you have left enough room in the oil tank for it to return when the engine is started next time.
However, where there is a slight issue is that the amount of oil on its way back to the sump when the engine is running depends on its viscosity which in turn depends on its temperature. Hence the advice to check the oil level with the oil at its full operating temperature which will minimise this amount of oil.
This is actually not a big problem for BSA singles but it can be a huge problem for more modern singles that use the same oil for the engine and gearbox. With my more modern singles, the oil tank will practically drain of oil when you start the engine and will only display the correct level after a long run when the oil is hot. For these bikes, it is all too easy to over fill the oil tank!