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oil leak - head gasket issue?

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oil leak?

I've been using the bike a little more and noticed what looks like an oil leak from the head gasket. Some oil had dropped onto the distributor. Should I be re-torquing the head bolts? The copy of the manual I have doesn't mention specific torque settings.

 

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I am assuming you have recently rebuilt or redone the top end. After my rebuild I needed to re-torque the head four times in the first 600 miles, having new bolts and freshly annealed new copper gasket

I think the Dominator Service notes have the torque settings, but since I printed them off over two years ago, my recollection maybe wrong.

Search a bit on this website and you should come across the recommended settings and, as important, the tightening sequence.

You should not just torque up, but loosen slightly each bolt before re-torquing to ensure a true reading.
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Generally it does pay to re-torque the cylinder head gasket after a recent rebuild. Alan is correct in suggesting that this might need to be done up to 4 times.
The choice of gasket material can be the cause of leaks.  Solid Copper gaskets need to be very carefully annealed or they will not seal properly. 
Similarly, a composite gasket will also allow the Black Gold to squeeze through any imperfections. 
Check out this diagram.

gasket 2

This shows what can happen if a composite head gasket is used on a Norton Twin engine. They have two weak points where crankcase pressure will push oil through the composite sandwich to the outer edge of the barrel/head joint.  The first being the push rod tunnels. Any splits in the gasket rings that seal the push rod tunnels will let oil straight past. 
The same can happen at the rear of the barrel where the oil return/drain hole passes through the gasket. For some reason, unless a solid copper gasket is used, there is no protection at all stopping oil from being pushed sideways inside the gasket in this area. It then heads for the nearest exit which happens to be the cylinder head bolt behind the spark plug.
I note in the photograph the head bolt behind the spark plug is wet with oil. Possibly agreeing with the text above.

 

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I have found the suggested tightening sequence and an alternative tightening sequence but the only number I can see for torque is 30 ft/lb - is this the same for all bolts? Is a 3/8" torque wrench more likely to access things than a 1/2" one? When I have changed head gaskets on 3.0 V6 Ford Essex engines I used Reinz gaskets and torqued to 30, 60 then 90 lbs. I appreciate that alloy motorcycle cylinder heads aren't quite as robust so I will need to take more care.

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When I had a C11g with a 300cc conversion I had problems with head gaskets - the overbore meant the piston was hitting the gasket. I swapped back to the original cylinder / piston and a new gasket and the bike worked fine - I didn't use a torque wrench on that. Am I being too cautious thinking I need to work to a specified torque figure on a 99 ?

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Some of the threads are likely to be somewhat compromised after all the years .i would use a small ring spanner about 6 inches long and just do up firmly and to the pattern. They will come loose in  50 miles anyway and need checking about 3 times till they settle . the 5/16 threads will need care and less force. I only ever strip threads when using a torque wrench !!.

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Cylinder base nuts (3/8") 06.2652 25lbs/ft

Cylinder base nuts (5/16") 60.2321 20lbs/ft

Cylinder head nuts & bolts (3/8") various 30lbs/ft

Cylinder head nuts (5/16") 06.7529 20lbs/ft

All in the Dominator Service Notes which are available on this Web Site & free to NOC members.

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It took me a little time to locate the torque settings in the service notes as I was looking for them in the cylinder head notes area.. If I try fitting a new copper head gasket from the club spares shop will it be ready annealed so I only have to worry about surface preparation?

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I had several hours to contemplate the oil leak yesterday - I displayed the bike at Bloxham Steam Rally. I the bright sun I realised that the oil leak was to at least some extent coming from the carb side rocker cover which I had disturbed a while previously when checking valve clearances.

 



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