Anssi said:A riding buddy had 2mm taken off his -05 YZ250 and that bike is running great.
I don't know about Kawi parts, but Honda heads are only about $55. I can have my head milled locally for $20. So even after milling, I can go back to stock for a total $80 investment. 2 mm seems like a huge amount to mill off a head. I measured my stock squish clearance at 0.060" and it went to 0.070" after a new Wiseco piston. So I had my shop take 0.020" (0.5 mm) to get down to 0.050" squish clearance. I haven't gotten the jetting sorted out, but it feels really good so far. Part of my reason for taking at least a small amount off the head is that I'm at 5,300 ft elevation.Anssi said:I'm approaching the first top-end change and was thinking about having the head machined for a bit more compression because I would like more grunt. I hear the stock heads have pretty low compression to take into account the crap fuel people put in the bikes.
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The real question is, how much to shave off the head? A riding buddy had 2mm taken off his -05 YZ250 and that bike is running great. Obviously I would rather not take too much and have the bike ping itself to death.
In my experience, yes. It seems that the minimum recommended clearance I've found is 0.035" and I suspect that's the minimum to avoid mechanical issues (someone else chime in here). You should be mechanically safe down to 0.040". Don't know where you'll run into detonation issues.Anssi said:If I confirm that 0.067", could I maybe have 0.4 mm taken off the head to get the squish to 0.05" and increase compression a bit?
Sounds like a good result :cool: .Anssi said:Also, the engine now runs as it should. Very cleanly, and has the bark that it should have. I was able to retard the ignition timing back to stock. There was not a hint of detonation with even the advanced timing, though.
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