1998 yamaha royal star backfires especially when decelerating

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HELP Just bought Yahmaha Royal Star Deluxe 1998 and now it wont start

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Yamaha XVZ 1300 Royal Star 1998

Hi, Cleavell33
COUGHING is usually caused by an air leak in the intake system and will generally have the same telltale signs, a wet or damp buildup of oil/gas seepage at the intake manifold to cylinder head or carburetor to intake manifold connection and in rare instances a worn throttle plate shaft and or seals.
POPPING or backfiring on deceleration is usually caused by a lean fuel condition or an air leak in the exhaust system and is generally located where black carbon soot is seen as a flashing build up from any joint connection. This condition can easily be remedied by removing and cleaning both joint pieces and reassembling with high temp silicone and torquing the exhaust clamp to the proper spec.
SPITTING is usually caused by a faulty accelerator pump and or nozzle, or the float bowl needle and seat leaking and overflowing through the main jet mixing well nozzle, or the air-fuel mixture screw is adjusted too lean.
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The primary cause for backfiring on deceleration is an air leak - if the baffles have been removed or modified or if the gaskets in the exhaust tract are not sealing properly, fresh air can be introduced into the exhaust stream causing a pop or backfire. Check your exhaust system - especially if you have recently had an oil change, since the pipe has to be removed to change the oil filter on this model.

Shaft drive vehicles do make whining sounds you do not hear in a chain or belt drive models. Some whining sounds(also speed related) deal with the brand, mileage,and pressure of the tires. This bike also has two 90 degree turns in the drive line. One at the motor and one at the final drive. This takes more energy for acceleration and causes quicker deceleration when you let off on the gas, even without using the brakes.

Usally nothing to worry about. Some after market mufflers will cause it to do this. I had a Triumph 900 that back fired and crackled when i decelerate, i had staintune mufflers on it.
Check the color of your spark plugs for signs of running rich or lean.

is it a straight thru exhaust, or is it just a head pipe with nothing attached? If it's just a head pipe, you need to get some sort of muffler on it or you'll burn your valves out from a lean condition. The backfire is due to the vaccum fed carbs that yamaha runs. They work wonderfully, but under heavy deceleration, the vaccum still feeds the bowl, and it builds up excess fuel, which eventually burns off as a backfire. If it were fuel injected, you could have the fuel map adjusted to lean it out under deceleration.