new wisco piston," to drill or not to drill"

70 marlin

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#1
my stock kaw piston has lube holes on the exhaust side of the piston© I'm picking up some nice new sharp cobalt drill bits© I've haven't had to do this procedure© and atemping it blindly with no instruction, other than a old piston, I'll be doing the drilling with a drill press & the shamfering with a dreamal stone, I'll use a vernier caliper & very flexble plastic ruler graduated to 1 mm© I'll get the height with the caliper and the with's with the rule© the with, I'll do a measurement from center of the pin hole© am i missing any thing?
 

Neil Wig

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#2
Follow Wiseco's Instructions

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

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#3
I knew there was a right way !

thanks!!!!!!!!!!!!!!!!!!!
 

BRush

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#4
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.
 

WoodsRider

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#5
70 marlin - Are you replacing the piston in your '99? George replaced the piston in March of '00. Knowing George, I understand why there are holes.
 

70 marlin

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#6
now I'm really confussed?

na, it not georges bike ! it's the 96© it really did'nt one either but I had a kipps valve proplem© that I had serviced and thought while I had her a part she'd get a new piston© being the fine mechanic that I am i have no Idea what a exhaust bridge looks like? all that I know is I have a stock 220 piston with oil holes in it ? HELP OH GREAT BIKE GURU's
 
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WoodsRider

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#7
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.
 

BRush

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#8
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.
 

70 marlin

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#9
Horse in front of cart this time :<¥

Thanks guy's for the extra effort! I really put the horse in front of the cart this time:eek: stopped by my favorite dealer ship and picked up my nice new wiseco piston© that they found for me someplace in Ct© ¥wiseco was out of stock¤ and low and behold holes pre drilled in the piston DUH, I feel so stupid! the last wiseco piston I put in, was for a older kx80 no holes drilled from wiseco, and I toasted the piston© so I wanted to make sure I was totally prepared!!!!! for the assembley of spudric's bike:D again DRN has proven beyond a shadow of doubt their worth to me ! THANKS OKIE© and all that has helped©
 

EricGorr

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#10
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.:)
 

70 marlin

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#11
Thanks Mr© Gorr!

After having my pizza @ my favorite dealership! with parts in hand© I start to finish the rebuild© with surgen gloves on© doing quaily work, with total sterile technique, four hours latter she starts second kick ! it's so nice to work on newer bikes! Thanks to all©:¤