downshifting skids :( suggestions?

[Cactus Jack]

Yeah I talked about popping after hearing that Dirtmax 150 sounding like a popcorn machine on decel on the dyno ... the fuel is exploding in the pipe so it's escaping from the cylinder unburnt ... if fuel was getting sucked in from the carb on decel it should still only burn inside the cylinder while both valves are closed and sealed ... meaning the engine would give intermittent pulls like a two stroke does on decel ... and that's bad news (poor valve seat sealing) ... Most stock engines only have their valves and seats done by machine and machining is far from perfect ... The seats distort from heat , just like the cylinder bores do so they don't seal until they are hand lapped , blue checked , and pressure tested ... Some engine shops pressure test their assembled reco'd heads after machining the valves and seats ... BUT valves rotate so they'd have to be tested at various points of rotation ... The simplest and surest way is to hand lap and blue check ... machinists are getting lazy and going for the quick buck at the customers expense these days ...