ET: Engine (Twin) Engine Oil Leaking Into Primary Case

[Martin Conachey]

Its. All very interesting. The engine is a 49 Rapide in a 51 C Frame. Rebuilt 9000 miles ago by Bob Culver. I’ve always run it on Silkoline Chatsworth 40. Very difficult to get now in Ireland, Last oil change had to use Motul 20/50 motorcycle oil.
I’ve always known my bikes have feelings, so maybe she is just making a protest.
i have 2 engine breathers fitted , never any leaks.

To fit the seal appears to be a job, not for mere mortals like me

 

[Bill Thomas]

Unless you wanted Belt Drive,
I would not use an Oil Seal.
Just my thoughts.
Cheers Bill.

 

[Bill Thomas]

Are you sure it's engine oil ?, Some Gearboxes have been known let oil out into the chain case ?.
All ways check all oil levels often !.

 

[Bill Thomas]

Just a thought, If it's done this after being left a long time ie Winter and you have "wet sumped ",
This can happen , But after draining the sump , I have found it does not do it again during the Summer .

 

[Cyborg]

Unless you wanted Belt Drive,
I would not use an Oil Seal.
Just my thoughts.
Cheers Bill.

Bill,
How often do you have to drain oil from your primary case…. if ever? I put a fair number of miles on my C twin and don’t recall it ever being an issue.
With the current bike I want to run a breather with a reed valve in hopes of getting a slight negative pressure in the crankcase, so thinking it’s best to have a crank seal. Probably a mute point given how much it will be ridden.

 

[Martin Conachey]

Thank you all for your comments,.. I will just follow the advice of EMG Steven’s and drain periodically

 

[Bill Thomas]

Bill,
How often do you have to drain oil from your primary case…. if ever? I put a fair number of miles on my C twin and don’t recall it ever being an issue.
With the current bike I want to run a breather with a reed valve in hopes of getting a slight negative pressure in the crankcase, so thinking it’s best to have a crank seal. Probably a mute point given how much it will be ridden.

Over 55 years of ownership , Same Bikes , 2 Twins and a Comet, Many Many times, It does not bother me,
I use it as an oil change !,
I don't ride much in cold / Bad weather.

Vibrac told us some years ago, With a Comet, Roll it back on Compression at the end of Summer,
If I remember !! ,
Which puts the flywheels in a certain position,
That has worked well for me, But I don't know the position for a Twin.
The Comet Bottom end has never been down since I rebuilt it in 1977, I have raced it and used on the road.
Now Worried SICK !, Hope I can take it off the road , If I build a BIG Comet ?.

I have tried a reed valve , Didn't work for me, But my engines are race spec', 10 thou Piston clearance !.

 

[Cyborg]

On a twin, either piston close to TDC would do. That puts the pin above the timing side mainshaft. I’m not convinced it makes a whole lot of difference. Oil can still find its way past the pump. The ports in the pump are only ( both) closed for a few degrees and that is where the pump gets most of the wear so over time it gets easier for the oil to get past. With the pin higher than the mainshaft, you don’t get the siphon effect of oil draining through the timing side shaft and down though the pin. I reasonably sure the oil scroll in most bikes isn’t that tight, so oil will still find its way into the sump eventually. If all is well, crank position may buy you more time. All just my opinion….

 

[Bill Thomas]

My problem is I keep thinking , One more ride before Winter,
And keep putting off the idea of no more rides,
I hate Christmas and all that Rubbish.
As the song says," just get me through Christmas " ?.

Bit like disconnecting the battery, I just buy new ones , They are very cheap.

You are right , Some years there is hardly any wet sumping,
Just dug the Special Twin out, After a few years , And is OK !!.
Strange things these bikes, No 2 the same ?.

But for the first time ever, One of the Dellortos Flooded,
I had run the bike up a few times in a few days, Sorted dirty points etc,
Got all my riding gear on, And there is petrol all over the place !,
Sorted that and a few days later ,
Went out and the rear Norton Disc was hanging on, Bugger !,
Only got to the petrol station, Had to come home,
Found another Caliper under the bench for 40 plus years !, Cleaned it up and it seems OK !.
The Gods are against me ?.

 

[Bill Thomas]

Thank you all for your comments,.. I will just follow the advice of EMG Steven’s and drain periodically

You don't have to drain it, Just take the level plug out ?.