Friend purchased a WR400 in pretty good condition, needed a few very minor things but for the most part, everythings there and working well Everything except the air filter.... it's not the very first thing I checked and the bike has been ridden by myself and some other prospecting buyers. The filter had disintegrated and most of it sucked into the engine by the time I got the seat off to check it. The inside of the carby was stained slightly yellow, cleaned it up as best I could. Jets and passages are fine, starts easier now and runs just perfectly. But who knows how much dirt and fine particles got through the engine I live in Australia where we have some very harsh dust particles. As of right now the bike is running fine, nice and strong with no visible smoke (yet). It was however ridden home (about 30km of tarmac) and thus sucked a lot of unfiltered air. I'm about to do a compression test to see where it currently stands, but as for standing it'll still happily hold my entire weight on the kickstarter (90-95kg) for at least 5 seconds without using the decomp. Disconnect carby, get it on intake stroke and blast through spark plug hole with compressed air? Run upper engine cleaner through it? Pull the head? (it is only a cheap buy so really...) Just ride it and not care?