Got a 99 with about 5350 miles on it.
Got it about 2 weeks ago now. Have not been able to get alot of use out of it yet.
Hubby said last week the gasket between pipe and head was fine. Well I took it apart today and put in a new one just to be sure. Took it for a ride and it still backfires. Had a real loud one when I let off in 4th to shift to a lower gear then to also put on the bake. Maybe it needs some sealant? What kind to get and do I put it between the gasket and the pipe or between gasket and head?
Does not have a specific time it likes to backfire. It does so on both low and high end of gears. So it has been hard to determine. Does not do it all the time as before but of course have not been able to ride for any great distance other than about 5 miles or so at a time.
I have installed a  #150 jet, new air filter, new float on order (other had a crack..hubby did a temp fix until Tuesday when other comes in) Goes in on Wed to have the plug drilled out for the adjustment screw. (I am scared to do it myself also they have to check the pilot jet as the stock one I think is stripped) New battery
Any ideas?

ELIZABETH THE CARBY ON THE 86 HAS A DIAPHRAM ON THE TOP OF THE PISTON VALVE IN THE TOP OF THE CARBY AND ALSO IN THE TRANSIENT ENRICHMENT VALVE ON THE RIGHT HAND SIDE IT MAY BE WORTH CHECKING FOR ANY HOLES THIS MAY CAUSE BACKFIRING BUT USALLY UNDER LOAD OR WHEN TWISTING THE THROTLE I THINK THE LATER CARB ARE THE SAME GOOD LUCK