AJS & Matchless Owners Club

I changed to the club copper gaskets a while ago - and have had a growing leakage problem. I changed back to the composite gaskets today and hopefully they will last

I saw in some threads that the copper gaskets are supposed to be 1.5mm thick but they are actually 0.88 - I also looked on the spares list and they now list them as 0.88 even though the picture still says 1.5. Mine measure just under .9 so are part of that batch

The question I have is would it be possible to use two gaskets on each side to make up the thickness ? I am having a hard time thinking why not but I am sure there must be a reason !

The important thing is that the cylinder spigot matches the recess in the head. Too thicker gasket may prevent the head lowering sufficiently to give a good fire wall and too thinner gasket may not allow the head to tighten down fully before the spigot fouls the head recess. I mention this only that the heads may have been skimmed at some time. Sorry if this is teaching egg sucking.
I tried the copper gaskets but also found they leaked oil. Never had any probs in thousands of miles with the coposite type. The only thing I found with the comp gaskets is that the push rod holes need widening or the gasket can foul/wear away the push rods when the gasket spreads. I believe its recommended that the copper ones need a viton 'o' ring fitted to the oilways but that didn't cure leaks either. The only advantage of copper gaskets, in my opinion, is that they are re-usable. But, how often does one need to change head gaskets. I carry spare comp types on long journies anyway, try anealing a copper one side of the road!

Thanks for the response - I may start carrying a spare set of composites as you do !

not sure about running 2 copper gaskets but i had the issue of the too thin copper gaskets 3 years ago when i bought some .
i have gone back to the composite head gasket and all is fine for me .

with those thin copper gaskets i found that the cylinder spigot was pushed up against the head and that was pretty much all that was sealing the joint between the two .

there could be the possibility of machining the spigot on top of the barrel down a bit in a lathe but youll have to measure the head recess and the spigot depth and the head gasket thickness in order to find the required amount to be removed from the spigot depth , but also at same time will need to check the piston to valve clearance to make sure they wont hit , because you may effectively have ended up dropping the head down by anything up to .040" closer to the pistons .
i think the spigot was about 2mm depth when i measured it on mine .
if you machine the spigot off and fit thinner head gaskets the compression will go up , so bear that in mind when it comes to which fuel you run the bike on and the fact you may encounter "pinking" when its got a heavy load on engine and you are on full ignition advance .

i had tried all combinations of base and head gasket , so even a thick base gasket didnt make up any difference in the wrong thickness of the copper gasket

i think the problem you will encounter if trying 2 copper gaskets stacked is that of a leak from the oil gallery feeding the cylinder heads , as that seems to be the most common area for an oil weep in the first instance .
if i were you id fit composite head gaskets and forget about the copper ones unless you can find genuinely 1.5mm thick copper ones .

you might get 1.5mm ones from amc classic spares

the composite gaskets are 1.7mm thick .

ian

I fitted some club copper head gaskets a while ago and I had a problem getting a small enough valve clearance on one of the adjusters. I ended up having to grind a little off the top of one of the valve stems.
I never even thought of checking the gasket thickness as I assumed, being club spares, that they would be right but the penny has just dropped. It is fortunate that I did not have the heads skimmed or the situation would be even worse. Almost 1mm thinner that the composite type!
The next time it comes apart it will be composites for me.
Selling unsuitable parts such as this really damages the club's reputation as most people assume that being run by experts in the marque that the parts are right for the job and do not object to paying a little more for peace of mind. Clearly not the case here!
I have not checked the club stock list but if any of these unsuitably thin gaskets are still in stock then perhaps club spares should bite the bullett and consign them to the bin. That is where mine will be going.

Jim

Hello

I'm getting some 2mm thick copper head gaskets made up by Ferriday Engineering. I returned the club ones as these were too thin (approx 0.9 mm). The barrels on my bike have liners fitted and the liner flange effectively makes the spigot higher. Mike (at Ferriday) could supply 1.5mm thick gaskets but these would give me less than 0.3mm clearance betwen the recess in the head and the top of the spigot. I supplied Mike with a spare head and barrel so I hope that the fit is spot-on. Steve Surbey can also supply copper gaskets (1.5mm) but didn't have any in stock when I asked. I will also use a copper based gasket spray (I can''t remember the name maybe Hi-Cote) and Mike suggested using a small piece of self-adhesive copper foil or "slug tape" around the rocker feed holes. The tape is 0.001" thick and used for wrapping around plant pots or screening electrical circuits. Hopefully a combination of the two will prevent any leaks.

I don't know if the club has drawings with dimensions of the head recess & cylinder spigot? Ideally I would have liked to replicate the factory fit.

Hopefully the gaskets will be ready soon and I'll let you know how it goes.

CAB