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#66083 - 08/17/06 10:37 pm Norton Commando 850 Cylinder Head Oil Leak  
Joined: Aug 2006
Posts: 36
Lloyd from Luck Offline
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Lloyd from Luck  Offline
BritBike Forum member

Joined: Aug 2006
Posts: 36
Wisconsin
My 1974 Commando 850 is leaking oil from what looks like the head gasket. I have a copper replacement and am in the process of tearing the the cylinder head off. Any suggestions or tricks for installing the new gasket? I am quite the motorcycle mechanic novice so please state both the obvious and the trade secrets.

Thanks


1967 Triumph T120R Bonneville 650
1974 Norton Commando 850
1956 Ariel Square Four
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#66084 - 08/18/06 12:43 am Re: Norton Commando 850 Cylinder Head Oil Leak  
Joined: Dec 2002
Posts: 706
beltdriveman Offline
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beltdriveman  Offline
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Joined: Dec 2002
Posts: 706
Norton produced porous heads at one time and later ones were vacuum impregnated......... I have no idea when the cure was initially applied but I suspect it was before 820 production so you should be OK.The Info could be in the NOC Commando Service Notes book. Trust your problem is the gasket but I really would suggest you buy a more modern material gasket....Mtr Hemmings would probably advise..Dont think he would want engines being returned due to leaking head gaskets.......AND dont forget to check the head face is flat BEFORE going and fitting it only to find you still have a leak. OH ANDjust as importantly... Tighten the bolts etc in the correct order to the correct torque AND Retorque after 50 or so miles..when the motor has cooled down and is cold once again!!
You should of seen the 50 or so new as cast heads in Motor Cycle Shop at one time..slung into a corner of the cellar for years.The alloy was crap.... more holes than alloy....Anyone welding fins onto them that stayed on would be a good welder!!! Not worth having them machined..25 plus years ago Uncle Ted was quoted well over 100 per head for 50 heads to be done and he still had brand, still in their boxes, RH6S heads that had cost 45 per head..well thats what I paid for mine and I bought a few at the same time.........Think a Yank bought the unmachined heads.
Oh well must get back to wondering why some manufacturers did not use std BS keys and keyways in the shafts and sprockets.......I went through why didnt they use std SAE or BS splines years ago......

#66085 - 08/18/06 2:47 am Re: Norton Commando 850 Cylinder Head Oil Leak  
Joined: Apr 2005
Posts: 242
VA Rebel Offline
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VA Rebel  Offline
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Joined: Apr 2005
Posts: 242
Northern Virginia
I've had better luck with the flame ring style head gaskets on an 850. Good idea to re-torque the head a few times after replacement. Skip the re-torques, and it will most likely leak.

Oil can creep up the 5/16" studs at the front of the head and create a leak. If the exhaust rocker boxes leak, it can appear that the head gasket leaked.

#66086 - 08/23/06 5:23 pm Re: Norton Commando 850 Cylinder Head Oil Leak  
Joined: Feb 2006
Posts: 63
freakinhungover Offline
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freakinhungover  Offline
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Joined: Feb 2006
Posts: 63
Lancaster, Ca
+1 on beltdriveman and making sure the surfaces are machined flat. also make sure the barrels flat too. also when you are taking the ehad off make sure you use your fingers to hold the pushrods as far into the head and roll it off the barrel carefully. ive heard of slipups where someone bends a puchrod then things are outta whack....

#66087 - 08/23/06 6:22 pm Re: Norton Commando 850 Cylinder Head Oil Leak  
Joined: Feb 2005
Posts: 622
Tom Sanders Offline
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Tom Sanders  Offline
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Joined: Feb 2005
Posts: 622
Winter Springs, FL
VA rebel is right on.

Use the flame ring gasket and re-torque the head 3-4 times after you put it back together. I don't know of set rule on this. I'd go about 10 miles to warm the motor well ... let in cool and re-torque. Then a run of about a 100 miles ... cool and re-torque. Then another 200 miles ... cool and re-torque. The head bolts should stop moving about the 3rd or 4th time you check them. Remember the 3 studs (pointing down when the head is on the barrel) are threaded into alloy and it is tough place (impossible) to get a torque wrench in there. Be careful when applying torque.


LONG LIVE LOCKTITE

74 Roadster 880cc
1962 Norton 650SS
75 Ducati 860GT
1968 Commando Fastback SN 126157
1975 Honda CB400f AHRMA racer #842
email addy: sargehopp@gmail.com
#66088 - 08/24/06 1:16 am Re: Norton Commando 850 Cylinder Head Oil Leak  
Joined: Aug 2006
Posts: 36
Lloyd from Luck Offline
BritBike Forum member
Lloyd from Luck  Offline
BritBike Forum member

Joined: Aug 2006
Posts: 36
Wisconsin
Thanks for the info. You guys have mentioned a flame ring style gasket. Can you point me to a web link where I could get a look at and purchase one? Thanks again.


1967 Triumph T120R Bonneville 650
1974 Norton Commando 850
1956 Ariel Square Four
#66089 - 08/24/06 6:13 pm Re: Norton Commando 850 Cylinder Head Oil Leak  
Joined: Feb 2005
Posts: 622
Tom Sanders Offline
BritBike Forum member
Tom Sanders  Offline
BritBike Forum member

Joined: Feb 2005
Posts: 622
Winter Springs, FL
old britts sells the flame ring gasket. Ask Ella to send it priority mail and you'll have it in a couple of days.


LONG LIVE LOCKTITE

74 Roadster 880cc
1962 Norton 650SS
75 Ducati 860GT
1968 Commando Fastback SN 126157
1975 Honda CB400f AHRMA racer #842
email addy: sargehopp@gmail.com
#66090 - 08/24/06 8:51 pm Re: Norton Commando 850 Cylinder Head Oil Leak  
Joined: Mar 2004
Posts: 5
norton57 Offline
BritBike Forum
norton57  Offline
BritBike Forum

Joined: Mar 2004
Posts: 5
FT pierce FL
Hello, not like me to get into these discussions,but as a long time commando owner and have several that have leaked. check the back valve cover,make sure the oil is not leaking out of there. i have had it leak there a lot more than from a head gasket. the cover gets warped from over tightning. check it on a piece of glass and make sure it's still flat. copper head gaskets may leak but they usually don't blow out like some of the others do. so thats my 2 cents worth


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