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From: "Jonhaddock@..." <jonhaddock@...> Date: 2007/07/19 Thu PM 06:07:51 CDT To: W650riders@... Subject: Re: [W650riders] Time for tune-up *** I concur ! ...and make sure your using good gas? Music Matty * Popping on shut throttles is caused by the pilot circuit en-richening screws being set too lean. which they HAVE to be for emissions. The carbs are otherwise jetted OK up to 6000 rpm when they go rich. If that sounds confusing remember that Constant Vacuum carbs ( CV) are opened or closed by the suction effect of the engine...open the butterfly throttles and the engine sucks in air and that suction lifts the carb slide. Your throttle cables are not directly connected to the slide, unlike on conventional slide carbs. Ergo, engine revs determine how much slide lift you get and thus which jets are working. The pilot fuel/air circuit works exclusively up to 1000 rpm at which revs the slide starts to lift, adding the needles controlling influence which increases as revs rise until by 3000 rpm, the needle is the predominant metering system. At 6000rpm the needles come right out and the bike is on pure main jets. These are intentionally too big to cut down noise...correct jetting produces a snarl so the over-rich engine note is somewhat muffled. This muffled high revs note stays under the noise regs and allows the mid-range exhaust note to be more robust. You need to adjust your pilot screws out ...there's notes on this in the files section. That stops the popping. The pinging is probably mechanical...many have commented but in an air-cooled engine where you sit on top of the heads, pinking is actually MUCH louder and nothing like the distant tinkling one hears in a car. A bike has a distinct and loud CRACK when it detonates. Jon
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