<VV> Spyder backfire problem

[kevin nash]

 If you have points and condensor, and begins "randomly" backfiring once in a while, always be suspicious that its the points and condensor
That needs replacing. If you have an electronic ignition, it might be failing slowly... kind of weird but it is one of the ways they can die.
Since you have black clouds coming out the exhaust during a blip of the throttle after prolonged idling, it does sound like you might have
A too rich of an idle mixture screw setting. Maybe try turning that screw in ¼ turn and see if it helps with the condition. If not, put it back the
Way it was.
Kevin Nash