Amal Carburetor Concerns in a 1970 Triumph Bonneville

Reader Contribution by Keith Fellenstein
Published on December 1, 2011
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1970 Triumph Bonneville Amal Carburetor Concerns

Q: My cousin gave me a 1970 Triumph Bonneville that was bordering on junk a number of years back. I restored it and it runs fine, however there is one ongoing problem. After it sits for a period of time, the carburetor idle jet stops up on the left side. After I take out the idle adjustment screw and open the orifice up with a .017 drill bit, then tickle the carb, the bike starts the first or second kick. The right side idle jet stops up, but not as often. The carbs are Amal Concentrics. The left side carb’s slow-speed jet is in the side behind the slow-speed adjusting screw. The slow-speed jet in the right side carb is screwed into the carb body, which means the float bowl must be removed to clean the jet. I am quite certain that the 10 percent ethanol is why the jets are clogging. My question is, why does the left side slow-speed jet (which is in the side behind the slow-speed adjuster screw) clog roughly four times more often than the slow speed jet in the right side carb, which screws into the carb body inside the float bowl? By the way, I use fuel stabilizer. – George W. Miller, Jr./via email

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