[hortoncode3]

Has anyone ever fixed this issue? The side of my engine looks like Niagara Falls which was cute and nostalgic on the old olive drab bike but now it’s worse and a terrible mess. I looked around Hitchcocks catalogue but I’m not super sure what I’m supposed to be looking for parts wise. I imagine the head will need to come off so I’m certain there must be other stuff to service/maintain while I’m at it.
 

[stinkwheel]

So leaking round the head gasket where the pushrods go through?

It's a balance of clearances in there. The head itself seals against a raised spigot on the barrel. The head gasket seals round the edge to catch any blowpast and seal round the pushrod tunnels. The thickness of the gasket needs to be such that the head makes good contact on the spigot at the same time as the gasket is sufficiently compressed. Tolerances being what they are, this doesn't always happen. There are a few ways to sort this out.

One is to measure the clearance between the head and barrel when the head is against the spigot with plastigauge or a similar compressable material. Armed with this clearance, you either select a head gasket which is just a little thicker or have a little machined off the spigot or inside of the head to match a gasket thickness. Mr H sells copper head gaskets of varying thicknesses.

Another is to just use one size thicker gasket and hope it seals...

Another way is to use a fairly thick gasket which is quite compressable. Mr H does a thoroughly modern cometic composite gasket which is mostly fibre coated in ?graphite? sealant with a fire ring to ensure a good seal round the combustion chamber and which has built in sealant round the pushrod tunnels. I have these on both my 350 and 612 bullets and they seal well. Perversely, my 612 leaks a little oil on the left side of the head with oil going down the stud from the head then creeping under the gasket. I keep meaning to have the head nuts grooved for an o-ring but it's not enough oil to really make much of a mess, just a very light amount occasionally.

Another I've seen is to get someone to mill grooves round the pushrod tunnels and open out the holes in the head gasket wider than the grooves then fit it with o-rings in the grooves.

[Paul W]

I had to refurbish the top end of my year 2004 350 iron engine because of a failed exhaust valve seat and burned valve. The bike had just over 3,100 miles from new. It came fitted with a composite gasket but as I’d read varying reports on their longevity I decided to change to a copper one, which I was more familiar with. I used a little sealant around the pushrod aperture as recommended.

All went well for a few thousand miles then one night when out with a couple of other RE riders, it suddenly sprang an oil leak - from around the pushrod area. I checked everything over and re-torqued the head fixing nuts but couldn’t find any particular reason for it.

I changed back to a composite gasket and later did the same again when I fitted a domed Meteor Minor domed piston, which increased the CR by quite a margin.

Despite the extra stress on the gasket, it’s been fine ever since. The bikes done another 20,000 miles and no sign of any leaks.

[AzCal Retred]

The standard composite head gasket leaves a gap between cylinder spigot and head. Actual cylinder sealing occurs at the base of the spigot. This creates as a hard carbon trap around the outside of the spigot and cylinder head, often impeding subsequent removal.

The "spigot" of the cylinder has often been used to create a gasketless head/cylinder seal. Some here have cut grooves around the pushrod tube passages and fitted O-rings to good effect when sealing directly on the spigot top. I believe one could simply use appropriate composite cork gasketing, carefully fitted to seal the pushrod passages too. Maybe a dab of grey "Moto-Seal" on the cork around the passages as well for cheap insurance.

[Adrian II]

Gasket-less + O rings for my Not A Fury and 350, but they both have alloy barrels which are easier to machine for the O-ring slots.

A.