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#73773 - 03/05/08 3:53 am What do they mean regarding a porous head on an 850  
Joined: Dec 2006
Posts: 536
yellow_cad Offline
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yellow_cad  Offline
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Joined: Dec 2006
Posts: 536
Folsom, CA
In the Norton Commando article in December 2006 Classic Bike magazine on page 73, Roger Meyers states, that porous cylinder heads are not unusual on 850s. He goes on to say that oil will weep from the front of the casting above the gasket. Has anyone experienced this and is there any fix? When my oil tank was at the full mark, I had lots of oil in this area. I am watching this now so I am greatly interested in just exactly what Roger is referring to.


Jim

1970 Triumph Bonneville
1973 Commando Interstate
1971 OSSA MAR
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#73774 - 03/05/08 8:26 am Re: What do they mean regarding a porous head on an 850  
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douglas Offline
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douglas  Offline
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australia
I imagine the oil tank level isn't relevant, unless you mean something else?? Douglas

#73775 - 03/05/08 5:21 pm Re: What do they mean regarding a porous head on an 850  
Joined: Aug 2001
Posts: 1,253
Dave Comeau Offline
Crew Chief
Dave Comeau  Offline

Crew Chief

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Hamilton, Mass. USA
Yes the article is just repeating an incredibly old fact that the castings were typically porous.
Some processes called for something like a rosin dip that sealed similar casting done.
This was also the case with old Lotus twincam aluminum heads (british castings in the 60's-70's)...porous and rosin treated.

In addition all commando heads and cases were painted to possibly to seal them up.
I learned about this in the late 80's when I was stripping gasket goo off the gearbox outer cover with methylene chloride type stripper and found it was also eating the "paint/coating" off the inside of the cover. This must have been how they coated polished covers...by painting the inside...
Later I found the heads and cases were all painted also.
Once you clean in a dip solution or bead blast them you remove this coating. Some heads may not have been fully treated from new if they leak.
Stripping the head is obviously only half the process if the sealer coating is not replaced. .
2c


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
#73776 - 03/05/08 11:27 pm Re: What do they mean regarding a porous head on an 850  
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yellow_cad Offline
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yellow_cad  Offline
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Folsom, CA
In addition all commando heads and cases were painted to possibly to seal them up.

Is there a paint or coating of some sort that can be painted on to the exterior of the head and basically baked on by the engine heat?


Jim

1970 Triumph Bonneville
1973 Commando Interstate
1971 OSSA MAR
#73777 - 03/05/08 11:51 pm Re: What do they mean regarding a porous head on an 850  
Joined: Aug 2001
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Dave Comeau Offline
Crew Chief
Dave Comeau  Offline

Crew Chief

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Hamilton, Mass. USA
It is pretty much up to what you want it to look like...
I have have had people send me "clean' heads for exhaust port repair that was slathered with spray can gray/silver. that would work but eventually will change color a bit and it doesn't look natural.

I use (all aproximate) 1 part hardware store radiator silver/aluminum paint, with 1 part acrylic enamel silver, with 5-10 parts thinner and a touch of isocyinate hardener. When this is sprayed on, it is almost not noticeable that it is there. Which is what I want.....a clean aluminum finish that doesn't corrode and turn dark.
The dark is what I refer to when you clean a head and see texture and color differences.
This is from spots where the paint has come off and the aluminum corroded a bit and changed color compared to the protected areas.
I will be mixing up a batch to spray my hubs for my dunstall atlas and dunstall commando, that I am now relacing their Boranni rims with new SS spokes. Hope to have them both ready for the INOA rally this july.

Just strip a case with stripper and you will..well see what I mean. those darker stained spots.... mad


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
#73778 - 03/07/08 12:24 am Re: What do they mean regarding a porous head on an 850  
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yellow_cad Offline
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yellow_cad  Offline
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Posts: 536
Folsom, CA
When doing a rebuild, does anyone ever powder coat thses heads in order to seal them up good?


Jim

1970 Triumph Bonneville
1973 Commando Interstate
1971 OSSA MAR
#73779 - 03/07/08 12:43 am Re: What do they mean regarding a porous head on an 850  
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norbsa48503 Offline
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Flint,Mich
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norbsa
1960 TR6
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#73780 - 03/07/08 1:57 am Re: What do they mean regarding a porous head on an 850  
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Kommandokenny Offline
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Kommandokenny  Offline
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McKellar,Ontario
Quote:
Originally posted by yellow_cad:
When doing a rebuild, does anyone ever powder coat thses heads in order to seal them up good?
I thought about this also, but I wonder if powder coating the head would impede the dissipation of heat from the head???? confused


If Norton made an airplane,would you fly in it?
#73781 - 03/07/08 10:01 am Re: What do they mean regarding a porous head on an 850  
Joined: May 2006
Posts: 49
Seeley Offline
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Seeley  Offline
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Joined: May 2006
Posts: 49
England
In the UK there is a company called ultraseal who can sort this out, they've successfully done a few heads for me in the past, and also on my friends 150 rocker boxes etc, to the extent that we now have all castings done before building the motors! i notice they have a US office too, so it might be worth a try!!

http://www.ultraseal.co.uk/index.html

#73782 - 03/07/08 12:26 pm Re: What do they mean regarding a porous head on an 850  
Joined: Aug 2001
Posts: 1,253
Dave Comeau Offline
Crew Chief
Dave Comeau  Offline

Crew Chief

Joined: Aug 2001
Posts: 1,253
Hamilton, Mass. USA
Quote:
Originally posted by yellow_cad:
When doing a rebuild, does anyone ever powder coat thses heads in order to seal them up good?
Yes I guess some might.
2c
To me...well this is like putting on a scuba diving wet suit before sex instead of a condom laughing laughing

The vacuum impregnation which we do here at work would result in an almost undetectable coating. Actually it primarily is intended to go where there are cracks and little pits and caverns. Where the cavern completely goes through are the ones of prime interest.


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
#73783 - 03/07/08 1:26 pm Re: What do they mean regarding a porous head on an 850  
Joined: Dec 2006
Posts: 76
mitchp Offline
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mitchp  Offline
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Joined: Dec 2006
Posts: 76
UK
Quote:
Originally posted by yellow_cad:
In the Norton Commando article in December 2006 Classic Bike magazine on page 73, Roger Meyers states, that porous cylinder heads are not unusual on 850s. He goes on to say that oil will weep from the front of the casting above the gasket. Has anyone experienced this and is there any fix? When my oil tank was at the full mark, I had lots of oil in this area. I am watching this now so I am greatly interested in just exactly what Roger is referring to.
My '74 850 has a porous head - oil seeps out through a pinhole in the casting behind the right hand exhaust rocker box. It was "Ultrasealed" by the PO about 5 years ago, but the leak came back. Fortunately the pinhole is just accessible and a blob of clear silicone sealant has done the trick.

BUT...oil at the front of the head is far more likely to be coming from the inlet rocker cover or oil feed banjos. Oil leaking from just about anywhere on a Commando head will appear between the exhaust ports on top of the third fin. For proof, pour a little water on the inlet rocker cover and see where it comes out....

Mitch


Minds are like parachutes - they only work when they are open.

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