Hello, I've go an 86 savage I bought in spring of last year.  It has about 19,000 miles on it.  When I bought it the bike had been sitting for years in a garage.  The bike fired up and ran fine just needed a battery and some fresh gas.  I got the bike home changed some filters, fluids, and cleaned it up.  Drove the bike for months with no problem.  One day I left for a ride, got a block down the road and realized i forgot my safety glasses.  Went back home hopped off the bike and ran inside to grab them.  I heard the bike die from inside the house.  Came back outside and the bike would just crank but wouldn't fire.  I noticed there seamed to be some fuel in the line going from vacuum side of the petcock to the intake tube.  After doing some research on here I decided to order a raptor petcock.  After installing the petcock the engine still wouldn't fire.  So I decided to replace the spark plug just in case.  The motor finally fired up and idled normally, however I soon discovered a new problem.  When I get the bike up to 55 mph it will cruise just fine, but if I try to go any faster the bike will completely cut out, and backfire all while slowing down until I back off the throttle.  After playing around with it I found that there is a certain point I can twist the throttle with no problems but past that point the bike will not run.  Back off the throttle and the bike returns to normal cruising speed.  This also happens if I accelerate to hard at any speed.  The other thing I noticed is that the bike backfires differently than it used to.  It now pops rapidly when you let off the throttle.  Also the bike used to back fire when I turned off the key and it was a strong loud POP.  Now when I shut the bike off, if it backfires at all, its a soft plop sound.  So far all I've tried is taking the carb apart and cleaning it, and adjusting the mixture screw.  I also changed the spark plug again and double checked the gap.  To be honest the carb didn't look all that bad.  The previous owner had messed with the screw before as it is stripped out a little.  I can adjust it from one extreme to another and I hardly notice a difference.  Are there any tests I can perform to narrow this problem down.  It almost seams like its a problem with the compression, since its backfiring a lot weaker but I have no clue.  Any help is greatly appreciated.