I just bought an old 1980 SX250 Twin. I thought I got myself an ok bike. I took it for a quick test ride and apart from it idle being too high and the handlebars being a bit bent it seemed ok. Let me say I am not a mechanic, not even close, apart from an oil change and few other minor things that is about the extent of my knowledge. After buying the bike and taking if for a longer ride I noticed heaps of smoke started coming out of the tailpipe. The smoke only comes out of one pipe. Also I noticed the idle is really strange it revs very high at times. I tried adjusting the idle screw but that didn't fix the problem it seems to stall and then when given a rev it idles too high, I thought the throttle cable may be getting stuck but when looking at it and spraying some wd40 here and there all looks good but the problem remains. The bike goes good and has heaps of power for a 250. Apart from the smoke & idle problem it is an ok bike, it does drop a bit of oil but not too much. Can someone tell me what is wrong with the bike from my description? Is the motor stuffed? Thanks for your help.