What damage can over filling with oil do?

[Big Lee]

I only ask cos I boobed & checked my oil level about 5 mins after I started & knocked off the bike. There was no oil in the sight glass so I thought I`d top it up As soon as I realised hoped I`d just filled it to the top of the sight glass but no, I couldn`t see the top of the oil
I drained out about 150ml ish & was wondering how much damage could that or more/less do to the engine?
Good job it`s easy to drop it out

 

[Deleted account 211025001]

In theory it shouldn't do any damage as excess oil should get blown out of the breather.

In reality it is possible to blow a seal due to increased crankcase pressure (particuarly true of big singles/twins where crankcase breathing can be marginal at the best of times). This happened to me once on an old Guzzi of mine.

Andres

 

[John Armstrong]

In theory it shouldn't do any damage as excess oil should get blown out of the breather.

In reality it is possible to blow a seal due to increased crankcase pressure (particuarly true of big singles/twins where crankcase breathing can be marginal at the best of times). This happened to me once on an old Guzzi of mine.

Andres

Williams had a 1200 RT that had been over filled by 100% The person wasn't aware of how to check the oil level, just added it like they would on a car

IIRC they didn't mention it being blown out of the breather, though they did say the engine didn't sound too happy. As you say, probably very easy to get a hydraulic lock somewhere in the engine

 

[cookie]

to blow a crank seal, wouldn't the cranckase pressure have to exceed the oil pressure at the main bearings?

often wondered about that.

 

[Deleted account 211025001]

to blow a crank seal, wouldn't the cranckase pressure have to exceed the oil pressure at the main bearings?

often wondered about that.

Mmmmmm........... I guess, in theory that's probably the case but the oil pressure would have to be uniform across the area of the seal and said seal would have to be perfect, no weak/damaged areas - actually, TBH, I haven't a clue what I'm talking about

On my old Lemon I put 1000cc pots and high comp pistons in. I blew two seals on that (correct oil level). It was cured by putting a sump extension on which I'm assuming reduced the crankcase pressure.

Andres

 

[nud1e]

Crankshaft oil seal

The rear crankshaft oil seal would leak if the boxer engine was overfilled with oil. On an airhead, you would note the oil weeping in the joint between the engine and gearbox, before the clutch started slipping. A rebuild would require a new seal and clutch.
Experience is a wonderful teacher.

 

[cookie]

Mmmmmm........... I guess, in theory that's probably the case but the oil pressure would have to be uniform across the area of the seal and said seal would have to be perfect, no weak/damaged areas - actually, TBH, I haven't a clue what I'm talking about

On my old Lemon I put 1000cc pots and high comp pistons in. I blew two seals on that (correct oil level). It was cured by putting a sump extension on which I'm assuming reduced the crankcase pressure.

Andres

god knows, well nud1e does anyway

and on a guzzi, the pressure should be more or less constant as the pistons don't move in and out together like a boxer, the worst offender in this regard.

sump extensions lower the pressure + allow the crank to spin out of the sump oil. critical performance enhancement for an old ditch pump

 

[davegs]

Over fill

Sell it quick I've got £20.00. waiting!.
(The bike not the oil)

 

[mandon]

the same thing happened to me....
i called our local autorrad and he said its not bad.....