[wessex_man]

Yes if between the barrel flange and crank cases a compression ring. They are actually listed  as fitted for model 9's removed for 90's. So why not 8's. The use of softened copper ring and wellseal aids sealing on poor surfaces which blow. As you say will also lower the compression slightly.  I wouldn't use blue hylomar for this purpose either.

[iansoady]

My Model 10 had a copper head gasket - just a simple ring - so I annealed it and refitted it. I know the theory is that a ground joint is superior but the gasket seems to do the job - aided by a thin smear of Wellseal, which I also endorse. Excellent compression although I have yet to road-test the bike.

Although I didn't succeed in getting my timing cover oiltight with it - Loctite 5922 with a thin card gasket eventually did the trick. Despite looking like something you'd scrape off your shoe, this does seem to be a very effective non-setting compound. I found a tube at an autojumble years ago and this is my first use of it.

WRT the spacer, if it's between the cylinder barrel and crankcase (not sure what you mean by top & bottom halves Andy) then I'd agree with Greybeard that it's a compression plate. These were used on lots of bikes eg later Velo Venoms which had the shorter barrel from the Thruxton.

[Greybeard]

If it's fairly thick then it could have been put there to reduce the compression ratio - possibly to cope with  low octane wartime Pool petrol? Just a thought. Unless a non-standard piston has been used with a slightlyhigher crown and the spacer was there to help with increasing the clearances.

Steve

[Andy Cubin]

I also found this spacer in-between the top and bottom halves.

Anyone seen one before?
Why is it there?

Cheers

[Andy Cubin]

Thanks for the tip Steve and I have found the answer to the invisible gasket in the manual - wish I'd read it first before making an arse of myself 

[Greybeard]

I wouldn't use Hylomar or any other silicon gasket goo where solidified bits of it can get into oilways or jets and block them, Andy. I've used Wellseal for years and would recommend nothing else. Used on clean faces with or without a gasket it's marvellous stuff - a tin of it for around £20 will last you a lifetime, though a tube is cheaper 

http://www.ebay.co.uk/itm/Stag-Wellseal-Jointing-Compound-/291691331498?hash=item43ea287faa:g:71kAAOSwEK9T23M2

Steve

[Andy Cubin]

Thanks WM,  would Hylomar do the trick?

Andy

[wessex_man]

Hi not normally they should be a good fit. We normally use a liquid gasket Wellseal developed by Wellworthy for the purpose, (though it's Stag's now).

[Andy Cubin]

Help folks,

On taking my engine apart, there appears to be no gasket between head and main cylinder - should there be one?

Worried from Wiltshire!