In 2004 Triumph deleted the security covers from the Carburettor’s slow idle mixture adjuster screw and changed the slotted screw to a “D” shaped security headed screw. Adjusting both types of screws is a fiddle: many tried using “Thumb Screws” developed for Keihin CVK Carburettors used on other types of motorcycles, but they found that the needle profile was not quite the same.
Brent Smith of New Bonneville LLC in the USA developed a very special Idle Mixture Thumbscrew. Unlike other thumbscrews on the market, they are EXACT replicas of the stock screw’s needle taper and length. This allows the years of knowledge gained from the Triumph Bonneville community to apply directly to these screws. What does this mean? 3 turns out on the stock screws equals 3 turns out with our Thumb Screws.
The knurled head is scored at 180 degrees for a clear, easy to see indicator. The heads are machined out to reduce weight and vibration susceptibility.
The “New Bonneville” Thumb Screws fits all new Bonneville, T100, Thruxton, Scrambler, America and Speedmaster models from 2001 to 2007. They are supplied in pairs.
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