Why is my engine popping and banging?
After 35,000 problem-free miles my Yamaha TDM900 has started to pop and bang on the overrun. The are no obvious airleaks and the exhaust valve clearances are all within limits. Alex Abercrombie, Southsea
Answered by Stuart Gaines, Yamaha technician As you say the clearances are OK, the culprit could be a device called the ‘coasting enricher.’ These bikes normally run very lean and if you shut the throttle off rapidly the twincylinder can cut out, so there’s a little spring-loaded valve that cuts the air off to keep it rich enough. It’s mounted on the left side of the left-hand carb under a screwed-on alloy cover. Pull it out and give it a good clean.