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hi guys-i have good my first duke a 6/83 600sl panther slowly doing it up but after a couple of short rides the back cylinder is dropping out and the spark plugs are black as-bike been seating for last 7 years-need to find someone very good with carbys in brisbane an on the northside.:cool:
 

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Just a guess.. it's running a bit rich.

Dropping a cylinder can be a flooding carb. It's certainly not the only possible cause but it's happened to me and on this model bike. The flooding is usually due to a faulty needle valve/seat.

The carb float levels should first be checked and if all is good (17.5/18.5mm on PHF36's) then you need to check the inlet needle/seat. Now.... how to do that properly I'm not sure, but here is how I did it.

Clear/translucent fuel line.. if you don't have it, get some for this test.

Connect the carb to a couple of feet of line.. connect the other end to the tank and fill the carb/line till full. Disconnect the line from the tank* and see how long the fuel stays in the line.. if the needle/seat is leaking it won't hang around long.. maybe up to 15 mins. The valve should be able to hold fuel there for quite a while, even overnight. That's not enough to flood the carb, true, but when the vibrations of a running motor are added... well, as I said, it's what happened to me.

The needle and seat were replaced, a couple of runs to bed things in.. she hasn't dropped a pot since.

* You can leave it connected too, just turning off the tank tap, but, having a leaky tap as well would nullify the test.

Best of luck..
 
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