Which Jet?

[Pecon]

Hi all

   I recently fitted my reconditioned 276 to my '55 GF plunger after an engine rebuild and while the bike is starting and running well it seems rich as the plugs are black and the exhaust smells rich. I foolishly forgot to check the jet sizes before refitting it but I did check the needle which was down to the last notch. I had thought about investing in some smaller jets to see if this might help but wondered if I should be looking at the main or needle jets first.

  The strange thing is that the concentric which was on the bike when I bought it also resulted in black plugs which is part of the reason I decided to go back to the original.

Peter

[iansoady]

Remember that main jet only really has an effect over about 3/4 open throttle so I would be looking elsewhere to start with - worn needle jet / needle?

[Triton Thrasher]

Is it true there's an Amal tuning procedure in the workshop manual (and service sheets)?

[Goldy]

According to the Amal ref book 55 A10 with 276 carb has 4/042-170 main jet and 4/061-107 needle jet. There is a lot of info on service sheet 708.     http://www.britishonly.com/pdf/bsa/sectionX_BSAservicesheetno708.pdf

[Pecon]

Ian I think that the needle jet will be my first port of call as looking at the figures Goldy gives mine seems to be one size larger as I found a 108 jet in the pieces which were returned so I am assuming that it was replaced with the same size. I will have to pull it off and check the jets before ordering a replacement. I suppose I could be barking up the wrong tree as while I had the bottom end rebuilt all I did with the head was to grind in the valves and just did a visual check on the guides although there is only a little light smoke on startup from cold which clears when warmed up. A friend who rode behind me did not notice anything unusual.

Peter