Oil leak from head gasket

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May 4, 2005
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I have an annoying leak that seams to be coming from the head gasket area. The engine has been rebuilt recently and ever since it seems to consistantly leak oil, as soon as the engine is warm and the rpms are brought up above 3500. We have tried 3 different gaskets including a copper one with no significant change. I have visually inspected the areas around the studs, all seems ok. The leak seems to be coming from the front left side, the valve covers were checked and they are dry, so I don;t believe they are the cause. Also the exhaust threads were redone at the same time. Any ideas of what may be causing this, one upside of all this is my boots are now completely waterproof, and if I ever run out of oil, I could just squeeze a pint or two out of them.
This often comes from the intake chest drain hole. It then runs around the cylinder and drips off the front fins.

I prefer the flame ring gaskets, but always use a small amount of gasket sealer around the pushrod holes and the drain back hole.
If the leak is at the front of the head and its not running there from other places you can bet its the two studs that break in to the pushrod tunnels. The oil comes up the threads, degrease them and Loctite them in. I always use the Norvil fibre type gasket by Reinz (I think you spell it like that) and fit it dry. Never failed me yet.
Thanks for the tips I will be taking the head off once again this weekend and will look at both your solutions. Will let you know how it goes.
you may have covered this already but have a very good look at the rear rocker cover. If it leaks from cover or round nyt, oil runs down through head & comes out at front & looks like head gasket
My 850 leaked around one of the studs that break into the pushrod tunnels after the last rebuild. I used some copper hi-temp RTV around the studs and a flamering headgasket and the problem went away.
There was a pooling of oil around both front studs on the cylinder side, the studs did have loctite already. While the head was off I took a straight edge to the head, and I observed some low spots, especially around the front studs, looks like I will take the head in this winter to get the head planed flat.

I switched back to the copper gasket and added the gasket sealer on both the cylinder face and the head face. Torqued the head as per manual

Took the bike for a run and although it did leak a bit, it was a marked improuvement from what it was before, I could live with it for the rest of the riding season. It even seemed to cure a bit of smoking I used to get in the left cylinder before the engine was completely warmed up.

Thanks again for all your advice.
I had a similar annoying problem on my 850, specially when the bike got hot on a long run, fine splatters of oil on the barrels and timing cover, but with wind force you can never tell where its coming from.

So, one day on investigating the breathing system, a new mod was made to overcome excess blowby...this involved tapping a air line connector into the top of the inlet rocker cover and running a1/4 hose down to the drive chain in front of the rear sproket....and the pressure relief actually eliminated all of the oil leaking. Yes, this is a dry Commando under all circumstances and I am happy!

According to la ong time expert on Nortons, the heads and barrels can be porous, and crankcase pressure will force small quantities of oil out. Replacing head gaskets simply doesn't cover that.

thanks for the info Mick, I will try that breather on the intake cover and let you know what happens.
Installed the breather on the intake cover, took the bike out for a 200 mile run and wow the bike was dry she didn't even mark her spot when I stopped.

What a difference, I have not seen the bike this dry in the 5 years I have owned her. Thanks to all for their advice.
I think a lot of the oil leaking issues are due to crankcase pressure. I know from experience that once I installed a reed valve breather
http://www.mikesxs.net/mikesxs-fuel_system.php?category_id=4.7, Part #15-0677, I eliminated just about all oil leaks. I still have a small leak somewhere in the head. It too, is a lot less since the new breather valve has been installed. Drill and tap the outlet for 1/4 npt 3/8 " barb and bolt it to the back of the air filter plate and you're all set.

I am unclear on how you mounted the XS650 Yamaha reed valve. The picture on the websites appears to have a flange mount to the crankcase. Could you post a picture or two?
I'll post this for ya JimC.....
The flange end is the outlet. You can see I have a brass barb in the outlet. You'll need to drill and tap for a 1/4 " NPT. Use a 90 degree elbow 1/4 x 3/8 barb and the hose to the tank will slip on tightly and easily route to the tank. The input is 1/2", same as the hose from the crankcase, so you will have a perfect fit there too.
Oil leak from head gasket

here's the actual part
Oil leak from head gasket
Thanks Gavin.

Unfortunately, I still don't know how to post a picture. I see the Img tab on the Post a reply, but I assume the photo must first be on a website. Kind of a catch-22. Don't know how to get my pic on a website to get my pic on a website. Kind of like shutting down the computer with Windows. First, click start!
The (Photobucket) information I gave in that link is now a little out of date, -as Photobucket have made it easier to use since then.

So this is the (slightly edited) more up-to-date version that I gave recently:


You will need to open an account with a photo album hosting website (I like Photobucket: http://photobucket.com/ it is free for the basic service and easy to use) and then upload your photos to your new album.

To insert photos directly into a message from your Photobucket album.

Select a photo by clicking on the individual photo 'Img Code' line (it will highlight and say = 'Copied'), then use paste (right click>paste) to place it into your message, there's no need to add the 'Img /Img' tabs as they are already included.

Repeat for each photo using the photo's own Img Code.

Finally...use the 'Preview' button to check the photos show correctly before posting.

Don't worry if you get it wrong though, as we can generally figure out where the problem is.

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