To locate the holes correctly:
1. Install the piston without rings.
2. Install the cylider. No gaskets required.
3. Reach in through the exhaut port, and scribe a line on both sides of the exhaust bridge.
4. Remove the cylinder
5. Remove the piston
6. Use the scribed lines to center the lube holes on the exhaust bridge (radially)
7. Use your ruler to locate the lube holes as specified in the Wiseco instructions (axially)
8. Drill and debur the holes
9. Assemble top end.
70 Marlin, I’m assuming that this is some other bike than your KDX’s? Reason I ask is that it that you don’t need to drill the Wiseco piston for a KDX. Drilling is required if there’s an exhaust port bridge which the KDX (mine, at least!) does not have.
An exhaust bridge is a ridge of material running vertically through the exhaust port that would divide it into two separate windows. I've never seen a '95 to '01 KDX with an exhaust bridge.
70 marlin, I have a '96 KDX. This last winter I installed a 225cc Eric Gorr big bore kit. The stock 96 does not have an exhaust port bridge. You mentioned that the bike already has a 220 kit in it, so if you have something weird - like a sleeved cylinder with an exh bridge (if such a thing exists) then I don't know. The EGorr kit uses a +0.040" overbore 220 Wiseco piston (750P4). I can understand someone drilling holes by mistake because there's this little yellow sheet of paper that comes with the piston which seems to indicate drilling is warranted, but a close reading will see that they are talking about cylinders with an exhaust bridge. I was uncertain enough to give Eric a call to be sure. His answer: "No drilling, now quit bugging me" (Just kidding :) actually he was polite and helpful ) .
Sounds like the first thing is to confirm whether you have a bridge or not.
Hi Pat,
Just to let you know, Wiseco now adjusts the shape of the piston to accomodate expansion. You can't see it but if you were to measure the piston with a micrometer that has a fine point, you'd see that the piston is smaller in diameter directly in line with the exhaust bridge. On your KDX, it has 2 bridges, one on each side of the main exhaust, separating the sub exhaust ports.:)