Cylinder head bolt oil leak

I am not sure that everybody above is singing using the same carol sheet.John is talking about his front barrel studs and Chris the cylinder head. Though both can have oil leak issues due to porosity, cracks or duff threads.

I had an Atlas cylinder head and barrel which both dripped oil from well-known weak ares when pushed hard. The cylinder head leaked from the rear right bolt hole, just behind the plug, due to the thiness of the casting. The barrel problem was due to some bright spark enlarging the two front 5/16" studs up to 3/8".....causing them to break through the pushrod tunnel and so giving the crankcase vapour an alternative exit to the almost useless camshaft breather.

Having visited the Triumph Factory and seen their vacuum resin impregnated cylinder heads I tried the ACME DIY version to try and sort my problems. Strangely it worked for a year and then I sold the bike.

On the cylinder head I de-greased and then heated up the offending area, with a gas torch, until water dripped on it sizzed. I then mixed up some Araldite goo and spread it over the suspect area. The hot metal makes the goo go very runny and then soak into the surface.

The barrels were given a simlar cleansing and heat treatment but this time I spread the goo over the stud threads and inside the barrel stud holes before winding the studs into place. The barrels were laid on their backs so that any excess goo pushed out by the studs stayed near their ends. Any excess was trimmed and wire-brushed away after the barrels had cooled. When the time came for re-fitting the head in place, I used a thin layer of High Temperature Silicon around both sides of the gasket in the pushrod tunnel area and also around the base of the two front studs.

John wrote.........................

'The stud in question breaks into the pushrod tunnel and I'm told oil makes its way up the thread and comes out 3 fins above the head gasket.'

Studs breaking into the pushrod tunnels must surely be the two at the front of the barrel. The two front cylinder head studs will only affect the exhaust ports in the head and the other ends are too far away from the pushrod tunnels in the barrel. The rear cylinder head stud is under the inlet valve area and nowhere near the pushrod tunnels.

The oil john mentions is inside the pushrod tunnels. It is passing though the damaged walls of the pushrod tunnels where the bottom ends of the front barrel studs have broken through. It is then leaking upwards past the body of studs until it reaches the nuts. Which are both sitting next to the third fin, top front of his cylinder head.

The attachments may help or you could try reading the DSNs.

IPreviously Phil Hannam wrote:

John wrote.........................

'The stud in question breaks into the pushrod tunnel and I'm told oil makes its way up the thread and comes out 3 fins above the head gasket.'

Studs breaking into the pushrod tunnels must surely be the two at the front of the barrel. The two front cylinder head studs will only affect the exhaust ports in the head and the other ends are too far away from the pushrod tunnels in the barrel. The rear cylinder head stud is under the inlet valve area and nowhere near the pushrod tunnels.

The oil john mentions is inside the pushrod tunnels. It is passing though the damaged walls of the pushrod tunnels where the bottom ends of the front barrel studs have broken through. It is then leaking upwards past the body of studs until it reaches the nuts. Which are both sitting next to the third fin, top front of his cylinder head.

The attachments may help or you could try reading the DSNs.

I to have this problem with the two 5/16 studs breaking into the pushrod tunnels in a 750 Commando engine. I wish my barrels looked as good as the ones in the picture. Mine are on the edge of the pushrod tunnels and the threads break into it.

I have built quite a few Norton twins some for racing and some for the road, the only time I have experienced leaks is with this engine I have with the studs breaking through.

I have Araldited the hole and inside the tunnel. I have also machined the two faces on the cylinder head where the studs come out and made special nuts with big flanges and used alloy washers which has just about sorted the problem.

As the barrels are on std bore I don't want to scrap them. Just crap machinig I suppose at the works.

Happy 2015 riding. Tony

The problem with Norton barrels started to get worse when the SS versions of the engine arrived. The SS cylinder heads needed the fatter SS pushrods to cope with the beefier valve springs and these pushrods, in turn, needed bigger tunnels to operate in. This might not have been a problem if the tunnels had been more precisely machined. It is almost impossible to find any two similar barrels (same year & size) that have near identical maching. The quiz picture in the November Roadholder illustrates this point quite well. You tend to feel that Stevie Wonder would have done a far better job if asked.

Apart from Aralditing the studs in place I have seen another desperate repair that seem to have worked. This was cutting the bottom few threads off the studs and then brazing them in place inside the respective tunnels. There is an arc welding rod available for disimilar metals which could probably be used in a similar way. They are very good at joining most other metals to barrel castings. Cleaning up the weld might be a bit time consuming.

My 73 850 had the oil leak from the 3rd fin up. Over the years I have bought 4 cylinder heads to to try to get one that didn't leak. I also tried welding, resin impregnation and just about anything to stop it, but nothing seemed to work. Only on my 4th head did I find one without the crack, and now I just get a bit of mist around the front studs and the tappet cover studs after a lot of miles.

The amount of oil that comes out of the 3rd fin crack is out of all proportion to the size of the crack- it really gushes out as the revs get up, leaving the bike plastered after a 50 mile ride, which makes me think that crankcase positive pressure is blowing it out.

So I intend to fit a PCV, probably the Yamaha XS650 to stop my misting aroud the the stud holes.

I wish I had tried a PCV before I spent a lot of time and money on cylinder heads as I feel pretty sure that would have stopped the 3rd fin up leak by geting a negative pressure inside tha engine.

On various forums most people have obtained good results with the Yamy XS650 one, but has anybody got an opinion on the one Norville sell? ( although it pains me to buy anything from Norville)

I use the Norvil one on my B44 but I did not buy it from them as its just a plumbers non return valve and cheaper from a plumbers merchant .

You will need 2 pipe connectors plus this (just an example)

http://www.amazon.co.uk/MISOL-BRASS-RETURN-VALVE-Vertical/dp/B00OIWAOT8/ref=sr_1_9?ie=UTF8&qid=1420712615&sr=8-9&keywords=water+non+return+valve

another example

http://www.amazon.co.uk/BRASS-CHECK-VALVES-NON-RETURN-FEMALE/dp/B007JX2NY2/ref=sr_1_16?ie=UTF8&qid=1420712615&sr=8-16&keywords=water+non+return+valve

I have the Yamaha one fitted to the timing chest on my 1970 750 fastback. I have it routed into small catch bottle resting between the engine plates below the carbs. it does collect some oil, more the faster you go. but the breather from the oil tank now passes nothing and the condensation from the engine does not now go back into the oil tank. I think the timing cover stores oil when the bike is being driven hard, leading to the oil travelling through the Yamaha reed valve. Jim Comstock in the States drills a 1/4" hole from the timing chest back to the crankcases just below and to the left of the oil pump to drain this oil back into the system.

Previously david_evans wrote:

I have the Yamaha one fitted to the timing chest on my 1970 750 fastback. I have it routed into small catch bottle resting between the engine plates below the carbs. it does collect some oil, more the faster you go. but the breather from the oil tank now passes nothing and the condensation from the engine does not now go back into the oil tank. I think the timing cover stores oil when the bike is being driven hard, leading to the oil travelling through the Yamaha reed valve. Jim Comstock in the States drills a 1/4" hole from the timing chest back to the crankcases just below and to the left of the oil pump to drain this oil back into the system.

I have two PCV valves fitted to my Commando F/bed both as close as possible to the crank case. These do help the leaks and breathing. I have all my bikes fitted with these and have used them for years, a good mod guys.

Tony

Previously john_holmes wrote:

I use the Norvil one on my B44 but I did not buy it from them as its just a plumbers non return valve and cheaper from a plumbers merchant .

You will need 2 pipe connectors plus this (just an example)

http://www.amazon.co.uk/MISOL-BRASS-RETURN-VALVE-Vertical/dp/B00OIWAOT8/ref=sr_1_9?ie=UTF8&qid=1420712615&sr=8-9&keywords=water+non+return+valve

another example

http://www.amazon.co.uk/BRASS-CHECK-VALVES-NON-RETURN-FEMALE/dp/B007JX2NY2/ref=sr_1_16?ie=UTF8&qid=1420712615&sr=8-16&keywords=water+non+return+valve

I am about to fit a one way valve to try to stop a cylinder head oil leak, in which breather pipe is it best to fit it to ? The engine to the oil tank or the breather pipe from the oil tank to the atmosphere ? Please can you advise.Thank you Alf

Hi - has anyone found a way of stopping oil leaking from the front right cylinder head stud. I've owned a couple of Mk2 commandos (850) and have never found a way of fixing this problem. The stud in question breaks into the pushrod tunnel and I'm told oil makes its way up the thread and comes out 3 fins above the head gasket. I've got an old police fairing and the oil spreads itself down the inside on the right. I've tried most things (bunging up the hole where it breaks through, using thread-seal. I've even made a special nut with groove for an o-ring) - no success. Any suggestions?

Cheers - John