Hey, What are the typical causes of a badly smoking two stroke? (Bring on the two stroke jokes you bastards :grin: ) It started a while ago though the bike was idling badly so I thought it was just carb related. Since then I've had the carb cleaned and tuned and it idles perfectly. Next suspect was some of the oil; I've been caught on longer rides and had to buy a small bottle of mineral based oil (yes, two stroke). Since then I've flushed that through with the semi-synthetic stuff I was using before without any problems. Same goes for the air filter, I did clean and re-oil it with the mineral stuff (might as well use it if I've got it) but since then I've cleaned and re-oiled with the semi-synthetic so that's out. Finally I thought it was the rings so after calling a few Yamaha dealers (the best response I got was "hmm... you'd be looking at... ohh let's say... 80PSI") I ran the compression test and got perfectly consistent 90s. For an engine that runs a compression ratio of 6.7 : 1 that sounds about rightish and is kind of backed up by the ever-so-helpful Yamaha team. So I've got no idea what else it could be? Ideas? What else should I be checking? Cheers.