Mercury single carburettor, gaskets and manifold

An excellent move. I have paper gaskets between the head and the manifold and a thick tufnol insulation one between the carb and the manifold.

Previously jonathan_clinkard wrote:

I have a Mercury first registered in 1970 and want to scrap the twin carburettors and set it up with a single 930 concentric. I have a manifold but would like to know if there would have been a thick gasket between the

carburettor and manifold to dissipate the heat or just a thin paper one.

hope someone can help, Joff Clinkard.

Hello The Mercury Never had twin carburettors, they where built as a Singel Carburettor model from day one, someone else has fitted twin carbs, a Mk1 concentirc 930 should do the trick and run better but use bosch W7DTC spark plugs you find the bike will start better and run more evenly and a nicer ride too, good luck with it all Yours Anna J

Previously jonathan_clinkard wrote:

Previously anna jeannette Dixon wrote:

Previously jonathan_clinkard wrote:

I have a Mercury first registered in 1970 and want to scrap the twin carburettors and set it up with a single 930 concentric. I have a manifold but would like to know if there would have been a thick gasket between the

carburettor and manifold to dissipate the heat or just a thin paper one.

hope someone can help, Joff Clinkard.

Hello The Mercury Never had twin carburettors, they where built as a Singel Carburettor model from day one, someone else has fitted twin carbs, a Mk1 concentirc 930 should do the trick and run better but use bosch W7DTC spark plugs you find the bike will start better and run more evenly and a nicer ride too, good luck with it all Yours Anna J

Hello settings L930/18 main jet 250 .pilot jet 25 . cutway side valve size 3.1/2 needle pos 3 needle 106. yours anna j

Hi Joff, I'm actually running a monobloc. Iwould start with the needle on the middle groove on the concentric and see how it goes. It's such a long time since I ran a concentric I really can't remember the needle setting. Have fun, the Mercury is a great bike.Probably the very best of the 650s.

Previously jonathan_clinkard wrote:

Gordon, thank you for the reply, that makes sense to me. Can I be cheeky and ask you, the needle position you would expect on a Mercury with a single carburettor? It would be good to have an idea of the setting expected? Many thanks, Joff Clinkard.

Hello Joff, according to the Norton publication P106/P the carb data is :-

Concentric 930 Main jet280 Throttle valve 3 Needle jet .106

Needle position central notch Pilot jet25

Just to be different.....I have put two insulated gaskets between the head and the manifold. The original Mercury decoke gasket sets just had paper washers.

Adding a bit to the carburretor settings saga. I have just purchased a new Premier Concentric for my Mercury and the recommended main jet is 240 to 250 depending on the air filter or not. This was a surprise to me as I had asked for a 270 jet but was informed that the smaller jet would be fine. Something to do with better manufacturing of the carburretor. I guess a plug check once I get it running will be fine.

Attached is the original Mercury sales brochure with settings as Ronald has noted. Plus the original manxman 650 had a 107 needle jet.

So did the last of the 650SS machines with 930 Concentrics. No wonder they drank fuel.

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Previously Phil Hannam wrote:

Just to be different.....I have put two insulated gaskets between the head and the manifold. The original Mercury decoke gasket sets just had paper washers.

Adding a bit to the carburretor settings saga. I have just purchased a new Premier Concentric for my Mercury and the recommended main jet is 240 to 250 depending on the air filter or not. This was a surprise to me as I had asked for a 270 jet but was informed that the smaller jet would be fine. Something to do with better manufacturing of the carburretor. I guess a plug check once I get it running will be fine.

Attached is the original Mercury sales brochure with settings as Ronald has noted. Plus the original manxman 650 had a 107 needle jet.

So did the last of the 650SS machines with 930 Concentrics. No wonder they drank fuel.

well in my parts manual for the Norton Manxman dated january 1961, the needle valve is noted has 106. centre notch, on amal 376/246.and 376/247 chopped monobloc and spark plugs KLG FE80 3 point plugs now very rare

So we gone for Bosch W7DTC witch are the same , I been runing on these for three years with no isuses there very good spark plugs, and they make for easy starting , and good running and 60 mpg at over 60 mph yours Anna J

I am running a single 32mm concentric on my Mercury with good results.