I got a 1980 jag 2000 and i recently put in the 1978 panther 500cc engine in it and i got it running good for a while with the jag carb on.. i just drilled out the jet in the carb to be the same as the 500's but the jag carb is a buttlerfly carb and the panther carb is a roundslide carb. It didnt run very well with the original carb but when i put on the jag carb it ran like new... but after i was riding it up and down the backroads and out in the fields testing it out it just died down to 5mph.. well i barely made it back and the clutch side piston had a pretty good size hole in it and the fan mag side was perfect still looked like new... Now i got a new piston and installed it on the bad side and i got it running again but i put on the original carb in fears of burning it up again. The orignal carb makes it run like crap though and i've cleaned it thoroughly and still the same thing... at first it will only go 10-15mph with now power then slowly the power will kick and get it up to about 40mph... Is there any way to adjust the roundslide carbs? how far out should the air screw be on it? Help would be apprieciated... Seasons over for me its 50 degrees outside now but i would like to have it running good for next year because old sleds are fun to beat around on.