Wet Sump Test

robs ss · Jan 17, 2023

With our recent spell of wet weather I have not ridden for over two weeks so was surprised to find today that the oil level was below the dipstick - unusual.
I have a cNw rear reed valve so wasn't overly concerned about starting with this oil in the sump but was curious.
So I drained the oil from the small plug hole to measure what I was putting back in the tank. 700ml - more that I would have expected.
I left it draining and waited for an hour or so then measured the steady-state rate of dripping. Six drips in 58 seconds.
Then pulled a plug to check crank position - pretty well near BDC. Aha!
So moved it to TDC and waited another couple of hours to stabilise and measured the drip rate. 6 drips in 156 seconds. Close to a third of the leakage!

I was already aware of this phenomenon from my single but had never applied this to the Commando.
I'll be kicking to TDC when parking from now on.
Cheers

KiwiShane · Jan 17, 2023

robs ss said:
With our recent spell of wet weather I have not ridden for over two weeks so was surprised to find today that the oil level was below the dipstick - unusual.
I have a cNw rear reed valve so wasn't overly concerned about starting with this oil in the sump but was curious.
So I drained the oil from the small plug hole to measure what I was putting back in the tank. 700ml - more that I would have expected.
I left it draining and waited for an hour or so then measured the steady-state rate of dripping. Six drips in 58 seconds.
Then pulled a plug to check crank position - pretty well near BDC. Aha!
So moved it to TDC and waited another couple of hours to stabilise and measured the drip rate. 6 drips in 156 seconds. Close to a third of the leakage!

I was already aware of this phenomenon from my single but had never applied this to the Commando.
I'll be kicking to TDC when parking from now on.
Cheers

We got rain and 30 knot winds staring again now where I live....the last month or so has been crap weather for both sides of the ditch

ashman · Jan 17, 2023

It's our wet season here, over a metre of rain up North Queensland so far and roads cut but that's normal for this time of the year, usual crys from all the climate change fools, I mean people but it's the wet season up in the tropics and also Cyclone weather, they get some of the highest rain falls up North than the rest of Australia.
Last year Australia got the wettest year in decades and our Murry and Darling River has got the best rain so far from decades of drought and was suffering, they needed a good flush out and our ground water has been replenished, long over due.

Ashley

Tornado · Jan 18, 2023

That method of putting engine to TDC was mentioned I believe on an OldBrits tech page I once read a few yrs ago.

But as you noted, you're only pushing back the time it takes to drop all the oil from the tank. My concern is not having oil in the feed line at startup. Even with a sump reed valve to return that oil quickly, you will still be running for a bit with little to no pressure until feed line fills up.

marshg246 · Jan 18, 2023

Tornado said:
That method of putting engine to TDC was mentioned I believe on an OldBrits tech page I once read a few yrs ago.

But as you noted, you're only pushing back the time it takes to drop all the oil from the tank. My concern is not having oil in the feed line at startup. Even with a sump reed valve to return that oil quickly, you will still be running for a bit with little to no pressure until feed line fills up.

Regardless of the crank position, the feed exit from the tank is above the crank so it can only drain the tank down to that level. The fed line can then empty, again regardless of the crank position. The crank cannot lose all the oil it contains no matter it's position so there is some oil for startup. Besides the reed valve, the return line will be (nearly) full so the oil tank level will come up a little quickly which will fill the feed line. So, IMHO, slowing the draining is still helpful.

texasSlick · Jan 18, 2023

Tornado said:
That method of putting engine to TDC was mentioned I believe on an OldBrits tech page I once read a few yrs ago.

But as you noted, you're only pushing back the time it takes to drop all the oil from the tank. My concern is not having oil in the feed line at startup. Even with a sump reed valve to return that oil quickly, you will still be running for a bit with little to no pressure until feed line fills up.

My strategy to deal with this, is to drain about 50% of the oil tank prior to winter layup. Then, when first starting after the winter, I replace the 50% oil, giving me about a quart in the oil tank, even if all the oil I left in the tank prior to layup, should drain to the sump.

Should I forget to replace the 50% oil before starting, I have at least 50% more somewhere in the system. That does not satisfy your concern, but it will prevent me from running dry until I realize my goof.

A further advantage of this strategy is, should the oil tank completely drain to the sump, I am dealing with only 1 liter in the sump, rather than two.

Slick

marshg246 · Jan 18, 2023

There are lots of strategies. My MK2A rider came with the terrifying one - a manual valve. Got rid of it.

Since I don't have a belt drive, and I do have a reed valve, my strategy is to simply not worry about it. If my main seal ever pops out (doubtful), it's just not a big deal - nothing destroyed and an hour or so to replace it.

EstuaryBoy · Jan 18, 2023

marshg246 said:
There are lots of strategies. My MK2A rider came with the terrifying one - a manual valve. Got rid of it.

Since I don't have a belt drive, and I do have a reed valve, my strategy is to simply not worry about it. If my main seal ever pops out (doubtful), it's just not a big deal - nothing destroyed and an hour or so to replace it.

My recently reacquired P11 came back with an in line valve.... That will be removed before I even consider starting it up. Ran it for eleven years without one, so think I can manage without one now....

marshg246 · Jan 18, 2023

EstuaryBoy said:
My recently reacquired P11 came back with an in line valve.... That will be removed before I even consider starting it up...

The 69S I recently finished had a check valve in the feed line when I bought it. It was supposedly a running bike. Fortunately, I didn't start the bike since the check valve was in backwards and had no way to open.

KiwiShane · Jan 18, 2023

If the engine has sat for a while... a few kick overs will quickly start returning oil to the tank to cover the gauze filter which inturn will fill the oil feed hose line via a Comstock Reed valve sump breather...or you drop the oil out of the cases and replenish the oil tank...the reality of gravity and a gear driven pump.

Tornado · Jan 18, 2023

My bike fully drops all oil below tank sieve within 10-14 days. My solution is a manual shut off valve with an ign cut out switch fitted. Works a treat.

KiwiShane · Jan 18, 2023

marshg246 said:
The 69S I recently finished had a check valve in the feed line when I bought it. It was supposedly a running bike. Fortunately, I didn't start the bike since the check valve was in backwards and had no way to open.

In my mind those things should be called restrictor valves even when fitted the right way around

Wet Sump Test

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