The 70-9711 o-ring (thick) seals between Amal Mk.1 carbs. and manifolds '70-on on 650's and 750's. This thick o-ring creates an anti-heat-conduction gap between the carb. and the manifold.
'76-on parts books have columns for two part numbers for the sealing o-ring: the Triumph number and a "Makers Part No.", in this case an Amal number.
The error puts Amal 622/101 in the "Makers Part No." column alongside 70-9711. This is wrong because 622/101 is a much thinner o-ring that cannot make the anti-heat-conduction gap. If used, there isn't a gap and cylinder-head heat is conducted through the manifold to the carb., causing problems such as a rich mixture caused by the hot carb. vaporising excessive amounts of fuel.
StuartMac
