Amal Concentric Mk1 carb on '54 18S
Posted: Wed Oct 03, 2018 11:30 am
Hi All, I have an early model 30mm Burlen Amal Concentric Mk1 fitted to my '54 18S. I bought the carb from a fellow club member a few years ago; he had bought it new a few years before but never used it. It works very well, giving good performance and tick over, but bangs and pops on the overrun. This forum and Surrey Cycles at Kempton reckoned weak mixture caused by too small a pilot jet was the issue. Surrey Cycles recommended drilling it out to 19 thou (no 76 drill is 20 thou, 77 is 18). Where is the jet? The early Concentrics did not have a replaceable pilot jet like later ones but had a pressed in drilled plug, probably located under a pressed in metal cap in the base of the main body. A copper wire can be passed right through the hole behind the pilot adjuster, and the 2 very small holes in the Venturi are larger than 19 thou, so wherever the jet/plug is, it is not easily accessible. Any ideas how I can access the offending part without causing damage, or should I richen the mixture using the pilot screw as best I can and live with any subsequent popping? Andy