markmad said:
IMO you are actually bedding your rings into the sleeve and not the piston, and a KDX does not really rev that high to warrant a forged piston.
Im not saying don't buy forged but don't be sold on peoples hype because at the end of the day no one has taken the time to analize the material differences in the 3 different pistons.
Maybe no one has gone through all the testing for this particular application, but it has been proven many times that forged pistons are lighter / stronger and just plain better than cast. Casting is a cheap way to get a decent product. Forging is much more expensive but gives much better dimensional and surface finish control, as well as control of the material's grain structure. Cast parts will always be heavier and weaker than a properly forged part.
There's also the whole quality thing. Look at a stock 220 piston next to anything and you can see it is crap. I'll have to take some pics of mine some day. The casting is very poor, especially for a part as critical as a piston. Mine was FREE and I won't run it, as I can envision one of the skirts breaking off as I kick the engine over.
As the the whole "doesn't rev high enough to warrent it", well, depends on the mods. My bike revs out pretty good, although I don't know the exact rpm. But lets say this. Stone stock, reved completly out in 6th I went 71.9 mph. After all my mods I went up 2 teeth on the rear sprocket, which should drop top speed. I pulled off something around 83 mph. It revs now, and I definitly would not want the low quality stock piston in there waiting to ruin my day.
On many bikes the stocker is just fine, and some racers even perfer them over aftermarket pistons. But the KDX220's piston is a well known weakness. After studying a new one up close and personal I would recommend everyone change it out for something better!
By the way, there is only 2 different pistons, stock, and Wiseco. Pro X only makes pistons for the 200. You could use one, but it might fit a little on the loose side. :rotfl: