Q Why won’t my R6 tickover?
My 1999 Yamaha R6 has started cutting out on tickover if I leave it standing for a minute or so. If I get rolling immediately it runs just fine; clean pick-up, no misfires, all good. But come to a halt and it just fades away, although it restarts easily. Robert Murray, email
Answered by Lee Towner, Moto Works After 17 years, parts of the carburation system will be getting pretty worn, while a tickover problem indicates it’s in the pilot circuit. Before you pull the bank of carbs off, lift the air filter out and have a look down through the carb venturis with the engine running. The needle valve design incorporates a rubber cone which works like a toilet cistern to seal off the fuel when it gets to the right level in the float bowls. As that rubber ages, it allows the fuel to bypass the needle valve, which allows far too much fuel through at tickover so it ‘floods’ the engine. If you can see droplets of fuel coming past the needle valve that will be the problem. If there’s none of that you’ll need to get the carbs off and give them a thorough service, maybe using an ultrasonic bath to break up any gooey deposits in the narrow passageways.