M/C2 Sq4 SU jet adjusting tool
Posted: Fri Jul 22, 2022 11:54 am
A friend purchased a 1956 SQ4 some time ago and has been slowly fettering various things to produce a very fine machine that has no oil leaks (thanks to the pizza dish mod) and runs like a dream. Being a retired tool maker/fitter and with many years experience restoring vintage bikes he passed this tip across to me to post as he is not keen on social media and didn’t want to post it himself.
The tip relates to adjusting the jet position on a SU M/C 2, with this tool he made up you can adjust the jet position without removing split pins etc that you need to do with a standard spanner, you can even adjust while the engine is running. I haven’t seen this type of thing before but it may have been forgotten in the mists of time. He made his up from a old 5/8” or 16mm 12 point socket and a cheap a shock adjusting tool.
The socket is cut down to remove the bit for the square drive so only the 12 point part of the socket remains. This is then welded (silver soldered) to the shock adjusting tool and finally the socket is cut down the middle to leave the two half socket bits concentric to each other.
Photo below shows the 1) finished tool 2) tool going around the linkage 3) adjusting the jet up or down to centre it properly so it doesn’t bind. Procedure outlined in the manual is followed verbatim and would probably be needed if cork gaskets were replaced or carby dissembled. His bike ran well before but after tweeking acceleration is smooth as, Thanks Greg for passing this on!
The tip relates to adjusting the jet position on a SU M/C 2, with this tool he made up you can adjust the jet position without removing split pins etc that you need to do with a standard spanner, you can even adjust while the engine is running. I haven’t seen this type of thing before but it may have been forgotten in the mists of time. He made his up from a old 5/8” or 16mm 12 point socket and a cheap a shock adjusting tool.
The socket is cut down to remove the bit for the square drive so only the 12 point part of the socket remains. This is then welded (silver soldered) to the shock adjusting tool and finally the socket is cut down the middle to leave the two half socket bits concentric to each other.
Photo below shows the 1) finished tool 2) tool going around the linkage 3) adjusting the jet up or down to centre it properly so it doesn’t bind. Procedure outlined in the manual is followed verbatim and would probably be needed if cork gaskets were replaced or carby dissembled. His bike ran well before but after tweeking acceleration is smooth as, Thanks Greg for passing this on!