Oil remains in the sump

[John Martorano]

Hi all,

As the title says, oil accumulates in my Airone sump and then drips out a very small hole behind the flywheel.  From running it for about two minutes, about a half pint dripped out. Does anyone have an idea what the issue is?

Thanks,

John

[PATRICK HAYES]

I'm flying. Reply more tomorrow. 

Look down inside the oil filler neck. Should see the scavenge return line tube. Does oil squirt out while running engine? If not you have a scavenge problem and need more testing. How much oil is in the reservoir tank. Should level at just the bottom of filler tube. Report. 

 

Patrick Hayes

Fremont CA

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[Miles Carnahan]

Behind the flywheel is the clutch service hole. It sounds like the screw that would hold the oil in the case is no longer in place.

For normal maintenance, you would remove that screw and let the oil drain from the clutch area of the cases then "wash" the clutch with mineral spirits or gas added via the access hole on the top of the case while working the clutch and using the kickstarter to turn the clutch plates (engine in gear).

But still a half pint of oil is too much and what Patrick is outlining is *why* do you have that much oil in the clutch area of the cases? So, make sure you have oil flow as Patrick describes.

Miles

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[John Martorano]

Hi Miles,

That screw is in place.  Here’s a photo of the hole directly below the flywheel/crankshaft with an oil drip.

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[Mike Peavey]

Out of curiosity? do you have an oil shutoff on the line coming out of the tank?

Mike Peavey

Sent from my iPhone

On May 16, 2026, at 18:06, John Martorano <johntma...@gmail.com> wrote:



Hi Miles,

That screw is in place.  Here’s a photo of the hole directly below the flywheel/crankshaft with an oil drip.

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[Alan Comfort]

If you do not have an oil shut off or if the oil shut off is left in the open position for more than a few days, then the oil in the tank will drain into the sump. Not a big problem, but can get quite messy (and smokey) when the engine is started. It takes a while for the oil pump to move the excess oil back into to the tank and while that is happening the excess oil can migrate into the clutch case and cause the clutch to slip. The subject hole is there to drain the excess oil. The "clutch rinse" will return the clutch to normal operation. make sure that the appropriate size screw with a crush washer is fitted in this hole before operating the motorcycle.

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[John Martorano]

Yep 

On Sat, May 16, 2026 at 4:38 PM 'Mike Peavey' via Guzzi Singles <guzzi-...@googlegroups.com> wrote:

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[vanuss...@gmail.com]

Take the one way valve that sits on the oil pump apart and clean  the inside. Will stop most dry sumping.

Op zondag 17 mei 2026 om 18:41:32 UTC+2 schreef John Martorano:

[Patrick Hayes]

On 5/18/26 02:42, vanuss...@gmail.com wrote:
> Take the one way valve that sits on the oil pump apart and clean  the
> inside. Will stop most dry sumping.

Yes, but be VERY careful with the internal control spring. The strength
of that spring is critical to allow the valve to open when the engine is
running but close securely when stopped. I have never seen a
replacement spring or the specifications for length and compression.

This auto valve resides under the raw aluminum cup screwed onto the
outside of the bronze oil pump.


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Patrick Hayes
Fremont CA
Falcone-NT and SuperAlce
www.motohayes.com

[jerry atric]

I consider myself a competent engineer/mechanic but I would leave the pump alone and fit a shut-off valve, you get used to them and the engine will gently remind you to open it after a mile or two. I put a 1/4inch domestic gas (heating gas) valve from a plumber's merchant in the feed line on mine; unobtrusive and 100% reliable

[John Martorano]

Thanks guys! All the oil is drained, all two quarters. So I’m on it today.

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