oil leak from cylinder head

Joined
Jun 1, 2007
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49
Hi Guys ,

many thanks to those who assisted with my front end issues a month back and all is well after replacing the incorrect spings ...

anyways ... bike is now running sweet and a real eye opener to a tripler like my self ... i am well impressed in how the commando handles and the lovely low down grunt .... a lovely bike to ride ..

problem i have is my pet hate other than smoking ... is oil leaks ...

I am getting oil leaking on top of the fins , one fin up from where the head meets the barrels in the front of the motor .... looks like but can't be sure coming from around the nuts (I believe they are nuts and not bolts ) that slot down into the cavity in the head at the front ... I hope that gives the picture as well as i can describe it ....

I am struggling to see how oil can get up the stud with the way the head gasket is and if it did would not look to be under pressure but just gravity from the push rod tubes ... any ideas would be helpfull

thanks

steve

apart from that a lovely bike to ride until parking and leaving oil all over the shop .... and my jeans which are now waterproof :)
 

L.A.B.

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snibor said:
I am getting oil leaking on top of the fins , one fin up from where the head meets the barrels in the front of the motor ....

I am struggling to see how oil can get up the stud with the way the head gasket is and if it did would not look to be under pressure but just gravity from the push rod tubes ...

There was a thread concerning these barrel studs recently: http://accessnorton.com/norton_commando1989.html as it is possible for oil to find it's way up the studs in certain cases (crankcase pressure?) especially if the stud drillings have broken into the pushrod tunnels (or the tunnels have been opened out too far by a PO?) so it may be necessary to use either a stud thread locking compound, others (INOA Tech Digest) recommend using gasket sealant on the threads?
The oil could just be leaking across the gasket face from the pushrod tunnel/s as they are quite close to the studs?

The composite type flame ring head gaskets normally seal better than the copper type, although I still put a thin smear of gasket sealant around the area of the pushrod tunnels on both sides of the gasket.
 
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May 13, 2007
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Oil seepage around the front 2 head studs is common. The threaded holes for the studs break into the pushrod tunnels. The cure for that is to goop some copper hi-temp RTV around the studs in the cylinders during assembly. I also use a light spray of copper coat on both sides of the gasket.

This always brings up the debate of copper vs flame ring head gaskets. Copper ones are more prone to oil leaks, flame rings tend to blow out.

YMMV
 

ML

Joined
Jul 30, 2007
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Oil leak from head

G'day,

This topic plagued me for sometime too. Turns out that Commando heads and barrels can be porous castings, when hot or under high revs can lead to pressurisation forcing minute amounts of oil out from the head or barrel and the wind force hitting the front of the motor tends to blow it all over the place making the source hard to determine.

I fitted a 1/4' breather to the upper part of the inlet rocker cover and it bloody well cured it. Principal cause is excess piston blow by overloads the standard breather arrangement. Got a nice dry bike no worries.

PS - read other related topics in back posts.

Mick
 
Joined
May 22, 2004
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522
ML /Mick

I agree wholeheartedly on your comments in regard to the pressure build up ~ and I just completed a lengthy post related to this very issue.

I also said personally to Snibor that I had this head oil problem after the engine was rebuilt in my 850 but it "took up" so I was of little help to Steve.

But I fitted a PCV to the breather line from the engine to the oil tank and my theory is essentially as you explain.

With the PVC valve my theory is that as it is a one way valve it minimises the intake of air on the up stroke but allows a maximum 'air expellation' (?) on the down stroke ~ additionally minimising the air pressure ~

This works for me ~ and most notably is the much cleaner crankcases little or no oil misting which was common on the rebuilt engine ~

Additionally I beleive this breathing mod reduces the pressure applied to such issues as the crankcase to primary seal ~

I like your thoughts and certainly be worth a try for Steve ~ rather than ripping the top end apart.
 
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