Explain dry-sump to me - does the sump auto level itself?

[PrivatePilot]

Hey all - I have a new motorcycle with a dry sump system, the first with this setup - all my previous bikes have been traditional pans.

It has a very specific refill procedure after an oil change with a certain amount of oil be added to the crankcase, and the remainder of the required volume being added to the reservoir.

However, there seems to be a great deal of debate amongst the owners of these specific bikes about how to maintain oil levels - some state that if you find the dipstick (in the reservoir tank) low (meaning the engine has used some oil, or it just needs some more added after an oil change and the first run) that you should "add some to the crankcase and then add some to the tank in equal amounts".

It's my understanding that a dry sump system more or less auto-levels the sump, is that not correct? So if the crankcase side of things was shorted (say, for example) 250ml of oil during the refill, that "missing" 250ml would be made up automatically from the reservoir after the engine has been run for a few minutes, and then you'd just refill *solely* the reservoir, not needing to worry about the crankcase level manually?

Is my understanding correct?

Is this "after draining and an oil change add X number of litres of oil to the crankcase directly" not just to ensure there's no oil starvation during the first start (not relying on the reservoir suddenly being forced to feed the entire oil demand post oil change) more-so than "leveling" the system from crankcase to reservoir in some way?

Thanks for the advice!

 

[ctechbob]

It sounds like that is exactly what they are doing when they tell you to add some to the sump. So the scavenge section of the oil pump doesn't run dry. After the bike runs for a bit of time, there shouldn't be anything left in the sump except for whatever the scavenge pump can't get. Everything should be in the holding tank.

That's typically how a dry-sump system would work.

 

[ZeeOSix]

What does the manual say regarding an oil change and adding oil to the reservoir tank? If there's only an oil level dipstick in the reservoir, then that's the the level to go by per the manual level checking procedure.

 

[barryh]

It's my understanding that a dry sump system more or less auto-levels the sump, is that not correct? So if the crankcase side of things was shorted (say, for example) 250ml of oil during the refill, that "missing" 250ml would be made up automatically from the reservoir after the engine has been run for a few minutes, and then you'd just refill *solely* the reservoir, not needing to worry about the crankcase level manually?

Is my understanding correct?

That's correct , just keep the oil reservoir topped up.

You don't mention the bike but with old dry sumped Brits, the problem was not too little oil in the sump but too much, as oil migrated down when the bike had been stood for a while. In those circumstances you wouldn't want to add more oil so best to do oil top ups immediately after the engine has been run to ensure any excess oil has been scavenged from the sump.

 

[Pete in PA]

Telling us what the bike is helps. I had a Honda XR650L that was dry sump. They are a real pain. If I remember right, start the engine, let it idle without touching the throttle for 5 min., shut it off, wait a couple min. then check. All while upright. (no centerstand)

Give me wet sump anytime.

 

[thastinger]

A true dry sump will have the oil dipstick in the oil tank. It will drain back to the sump over time, which is why you have to start it up first and let it idle for a few minutes before you check the oil level.
Most will have a 2 sided oil pump, half of the pump moves oil from the sump to the tank and the other side pumps oil throughout the engine. The crankcase is never empty of oil but the level is low enough that the crank doesn't spin through the oil.

 

[PrivatePilot]

Thanks everyone.

A true dry sump will have the oil dipstick in the oil tank. It will drain back to the sump over time, which is why you have to start it up first and let it idle for a few minutes before you check the oil level.

This pretty much echoes the owners manual for this bike - start engine, let run for a few minutes, shut down, and check dipstick with bike level. Which is a bit difficult since it's a 1000# bike and all that, but yeah, manufacturers seem to think we can perfectly balance a bike and remove, wipe, replace, remove, and read a dipstick while holding that 1000# bike level and upright lol.

Telling us what the bike is helps.

2018 Yamaha Star Venture transcontinental. It's a very uncommon bike.

 

[bonjo]

dry sump system stores most of the oil in a reservoire higher up like the frame (in my case). There is still some oil in the crankcase pan. One benefit is that it provides a higher ground clearance.
If the bike is left standing, then some oil can leak from the reservoir into the pan therefore giving you a false level reading.
You can either follow Pete in pa's suggestion or like me check the oil after within a couple of minutes after the bike has been ridden.
The oil change procedure is also different

 

[Kira]

If the bike is left standing, then some oil can leak from the reservoir into the pan

Leak or just drain? just askin'.

 

[KrisZ]

I would not sweat a dry sump oil level check that much. The oil is in the reservoir so no risk of the oil foaming when overfilled.
The only issue with gross overfill would be the oil overflow from the tank once the oil starts pumping and there is no room for the return.

The engine will always get the proper amount of oil as long as there is enough in the reservoir and no air is sucked in. So being a little bit over or under is not really that crucial for normal riding.

Now if you redline the engine a lot or use very high RPM often, then I would want to be as close to the max line as possible, otherwise as long as the level is somewhere between the min and max, it will be fine.

 

[Malo83]

 

[bonjo]

Leak or just drain? just askin'.

I used the term leak because the oil should stay in the reservoir. Looking at Malos's picture, could be the pressure relief valve staying slightly open.
You can check the oil level as per owner's manual and again after a day or two without running the engine to see if the level has dropped. This will give you a baselien reference

 

[DriveHard]

Thanks everyone.



This pretty much echoes the owners manual for this bike - start engine, let run for a few minutes, shut down, and check dipstick with bike level. Which is a bit difficult since it's a 1000# bike and all that, but yeah, manufacturers seem to think we can perfectly balance a bike and remove, wipe, replace, remove, and read a dipstick while holding that 1000# bike level and upright lol.



2018 Yamaha Star Venture transcontinental. It's a very uncommon bike.

Make a small block of wood to put under the side stand that gets it very nearly to vertical without going too far. A slight lean (just enough to keep it stable on its own) won't change your reading, and give you both hands to check the dipstick.

That along with a stick to stick under the right rear axle nut to just lift the rear tire off the ground so I can oil the chain by tripoding the bike up on the front wheel and side stand work great as simple carry along tools for a road trip.

 

[dumkid]

Just keep oil in the reservoir and you should be good.

My grandpa's ktm 990 adventure bike has a dry sump. One of the relief valves failed, over pressuring the resivour and and pushing oil out. His solution (he was on a road trip) was to remove the little valve, which let the oil drain from the reservoir to the sump after sitting, so with thick oil and it all in the sump starting it was extra fun. Once it got running the oil would pump back into the reservoir