650SS head gasket and pistons

hillbone

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Hi. I need to replace the head gasket on the Dunstall 650ss with high compression pistons. Which gasket would suit the best? I see theres a spigot and non spigot. I'm clueless on the difference.
Can anyone identify the pistons please?
Im hoping theyre the correct Dunstall 10.5.
I Can see that the piston on the left has some poor timing damage.
cheers Hillbone.
 

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You have a spigotless (flat) barrel.

Andover Norton offers a composite gasket only for this model.
andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk

A copper gasket is available from Norvil:

The Norvil Motorcycle Company supply spares, accessories and parts for Norton and Norvil bikes

Online secure shopping by the Largest Exporter of Genuine Norton and Norvil motorcycle spares, accessories, components and replacement parts in the World
www.norvilmotorcycle.co.uk
(look up "search our site", select "gaskets")

I am not sure which gasket Dunstall prescribed - my guess is the copper head gasket. Look up discussions on head gaskets at the NOC club site for recommendations and installation tips.

- Knut
 
Knut: Perhaps it is the lighting, but those cylinder liners appear to be proud of the cylinders, making these spigotted cylinders. The spigots are the liners that stand proud of the cylinders by about 0.010 inch.

The domed pistons appear to be consistent with 10.5 CR .I cannot identify as Dunstall, but could be.

Solid or composition gaskets are a matter of choice ...... I have had leaks on both. Currently, I am running Solid using Jim Schmidt's 0.005 copper wire technique on the under side. No leaks so far..

Do a search on head gaskets by author jseng1 for the wire technique. I am hesitant to use the wire on the upper side of the gasket as I am concerned the copper wire may indent the aluminum head. See https://www.accessnorton.com/Norton...s-a-head-gasket-2015.20190/page-2#post-388162

Check the head for flatness before refitting.

Slick
 
Last edited:
Example of "spigoted" barrels (Atlas). Deleted from engine number 114870 (10/65).

Atlas Barrel - rebore to +0.060, hone or ditch?

Hello guys May I ask for your advice concerning the barrel for my Atlas project bike? The engine was seized when I got the bike and I managed to remove the piston that was stuck. The barrel is in good condition but one of the bores is pretty rusty and I was thinking of getting it bored to the...
www.accessnorton.com www.accessnorton.com
 
L.A.B. said:
Example of "spigoted" barrels (Atlas). Deleted from engine number 114870 (10/65).

Atlas Barrel - rebore to +0.060, hone or ditch?

Hello guys May I ask for your advice concerning the barrel for my Atlas project bike? The engine was seized when I got the bike and I managed to remove the piston that was stuck. The barrel is in good condition but one of the bores is pretty rusty and I was thinking of getting it bored to the...
www.accessnorton.com www.accessnorton.com
Click to expand...

Good picture..... nothing ambiguous about those spigots,
 
texasSlick said:
Knut: Perhaps it is the lighting, but those cylinder liners appear to be proud of the cylinders, making these spigotted cylinders. The spigots are the liners that stand proud of the cylinders by about 0.010 inch.

The domed pistons appear to be consistent with 10.5 CR .I cannot identify as Dunstall, but could be.

Solid or composition gaskets are a matter of choice ...... I have had leaks on both. Currently, I am running Solid using Jim Schmidt's 0.005 copper wire technique on the under side. No leaks so far..

Do a search on head gaskets by author jseng1 for the wire technique. I am hesitant to use the wire on the upper side of the gasket as I am concerned the copper wire may indent the aluminum head. See https://www.accessnorton.com/Norton...s-a-head-gasket-2015.20190/page-2#post-388162

Check the head for flatness before refitting.

Slick
Click to expand...
Thanks Slick. Always reliable feed back. Gettin there slowly on this bike.
 
I had read on the NOC site that the composite (fiber/copper combo) was preferred. I personally have had better luck with the composite on my 600. I have a spigot cylinder.
 
kernel65 said:
I had read on the NOC site that the composite (fiber/copper combo) was preferred. I personally have had better luck with the composite on my 600. I have a spigot cylinder.
Click to expand...

I have read that also, and that is the opinion of Comnoz too.. I think the flatness of the head may be more important. I think Jim Schmidt's wire trick will work with either type..
Also, retorqing several times after fitting a head, may be an important factor.

Slick
 
Be careful, I am aware of several occasions where replacement pistons [mine were GPM] needed relieving as the skirts hit the flywheel.
 
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