Thread: 2009 ktm 400xcw
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Old 11-17-2012, 01:09 PM   #9
gatorgrizz27
Gnarly Adventurer
 
Joined: Jun 2008
Location: Austin, TX
Oddometer: 131
There are very slight, as in less than 0.001" variances in machining the cylinders and pistons when they come from the factory. Basically KTM sorts the cylinders and pistons by slightly under or over specified size, and matches them. You will have to mic your bore to be sure which size it takes, the service manual should tell you the limit. Last one I did I asked a very reputable KTM mechanic that is a buddy of mine if I could just buy the larger size piston since the bore would have worn enough that either one would fit. He said no, the Nikasil really doesn't wear at all, and it is important to mic it before you order the piston. It sucks to have to tear it down and leave it apart for parts.
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