The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: worntorn on 09.05. 2017 13:46
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I'm having some Cometic gaskets made up for the SR.
These are aluminium with nitrile rubber sprayed on both sides. Total gasket thickness is .043". They will handle heat up to 300 F. I'm thinking of ordering Cometic for the primary , outer and inner timing, trans , tappet covers, carb intake, and possibly cylinder base. I've used these on the Vincents and they worked wonders. Aside from the total seal of a less than perfect surface, they have the advantage of being reusable many times.
Are there some other A10 gaskets that would be good candidates for the Cometic treatment?
Glen
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A10s seem to leak all over the place, however I have had some solid copper gaskets made up for the rocker boxes, which thankfully, stop the leaks from there, I also had some much thicker ones made for M20/21 cylinder heads whichhare also sucessfull, I recently found oil on my A10 head that I thought was from the rocker box but turned out to be coming from a leaky fork seal. what a releif that was. all I need to do now is try to cure a leaky tin chain case on a Matchless G9. *smile*
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Rocker box and tappet covers would top my list.
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Would the 300 F heat limit be adequate for the rocker box gaskets?
Glen
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You don't know it, but I owe you an apology for thinking you were repeatedly misspelling "cosmetic".
Richard L.
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Glen,
I don't see the nitrile on aluminum material at 0.043" and 300F. I see 0.060" at 250F (the AFM product). What am I missing?
Richard L.
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Richard, the Cometic gaskets I have here measure at .043".
The 300f was from memory, now I'm wondering if 250f is the correct number. The bell is ringing a bit on 250.
Glen
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Glen,
I had never heard of them before your post. This is the company and page I found. http://www.cometic.com/p-35446-custom-gaskets.html
Richard L.
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You don' know it, but I owe you an apology for thinking you were repeatedly misspelling "cosmetic".
I do like an occasional 'comedic' interlude, but have to ask; Richard is that rouge you're wearing *red* ? *smile*
I have to admit though, when i first read it I fairly much thought the same thing *smile*
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Indeed, if you look at how an S7/S8 Sunbeam leaks so copiously you can see that the gaskets really are only cosmetic - and if it's someone else's bike - comedic also.
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Bum Bum!
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I found out about Cometic gaskets from the Chicago Vincent Section. They had 20 or so sets made up and offered them to club members at cost, so I tried them on my leaky Vincents.
After seeing the results of that experiment, all my bikes are going to be wearing Cometics.
I don't care if it makes them look a little trashy. Just like Confederate Railroad, I kind of go for that.
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What will be the price of these gaskets and the whole set actually? How do you arrange it with Cometic or they have the data already?
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You don't know it, but I owe you an apology for thinking you were repeatedly misspelling "cosmetic".
And me too - sorry
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I've just now sent the gaskets off for copying.
I sent them the primary, both timing,gearbox, tappet cover, mag flange,sump and a couple I've forgotten. I'm trusting them on price as they were very reasonable on the Vincent gaskets.
Will report here once I receive the Cometic gaskets and invoice.
Glen
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I was talking to a friend who said a few months Back he sliced his palm open on the edge of one of these gaskets. 6 stitches I guess.
He swears by them but says you have to be carefull, the edges are very sharp especially if they pooch out and are exposed after install.
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Makes sense, and they are also nasty to trim if needed. A razor knife and patience are required. But once fitted they sure dry the bike up.
Cometic will have profiles on all of the A10 gaskets I sent them, should other A10 owners want to give them a try.
Drew at Cometic said they already had some of the A10 info from previous orders. They also have profiles for some A65 gaskets.
The gaskets he is sending are 32 thou thickness. I don't know why my Vincent gaskets measure at 44 thou, they don't list that thickness.
Glen
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OK, I admit that I do not thrash my A10 * but my machine doesn't leak oil. I use Blue Hylomar, sometimes only on one side of the gasket. I'm pretty sure that Hylomar would seal just as well on its own. I made sure that mating surfaces were flat during rebuild. I do not use Allen screws/bolts; just slot-head screws. Surely my machine is not unique.
* I also have to remind myself that the bike was off the road for forty years so has not had the constant abuse that some of these bikes have had.
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I guess the main benefit is the Cometic's ability to seal a much less than perfect surface without any type of goop added.
There is also the ease of removal and reuse, plus these gaskets do not accidentally tear as paper gaskets do. This was a very nice feature when I had to remove my Vincent primary cover roadside, 1500 miles from home.
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I've used copper gaskets on my rocker boxes and am very pleased with the oil tight results and reusability after annealing. I think they'll stand higher temperatures than anything coated in nitrile rubber.
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Something that occurred to me while taking of my Timing cover the other day, is that some of the mating surfaces are thin (narrow) and don't mate evenly, in that they overlap each other.
The main culprit on mine is the joint between the Generator Drive chamber and the Oil Pump, which was only about 5mm wide, and mated for about half of that.
To rectify it I had a bead of weld done on the oil-pump (under)side and dressed it down.
It seems to have done the trick
I expect the Cometic gaskets would be wide enough to cater for this, but something worth keeping in mind and checking your own.
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The Cometic gaskets have been shipped so Cometic now has most 57-63 A10 gaskets on file.
I added a 1975 Commando primary gasket to the order as they already had the info for that. To be sure we were talking about the same gasket, I took a pic of a paper version I have had in storage for a few years. The paper gasket broke in two places while handling it.
The material has become very fragile even though it was stored flat and in a drawer.
This is one of the big advantages to the Cometics, they do not seem to degrade and will not break from handling, even accidental rough handling.
The total cost for the order was $141US.
Tappet cover gaskets are $7 each. The outer timing cover gasket was $28, so they are a bit spendy, but well worth it in my view.
Glen