BannedCR500Riders.com

When drilling those oil holes in the piston, how far below the lower ring should the first hole be drilled, how many and the distance between them? Also what size should they be drilled out to?
Thanks.

Wiseco link below. Click on the "M-Series Piston Installation" link.

http://www.wiseco.com/InstallationManuals.aspx

The size and position of the holes isnt super critical.

Getting them centered on the bridge is...

Take you time.

AlisoBob wrote:The size and position of the holes isnt super critical.

Getting them centered on the bridge is...

Take you time.

I like to drill 'em about .100 (2.5mm).

Make sure you remove the burrs from the inside of the piston when finished.

Another thing that I like to do thats an old school procedure is take you some 320 grit paper , and lightly chamfer all the sharp edges on the piston skirt. Alot easier on the break in

Yup, listen to AJ....

I don't run the holes.

However the instructions say .300 from the bottom ring and holes to be .060-.090.

...then your exhaust port bridge is relieved. The holes lubricate the un-releived bridge, keep it cool and stop it pinching the piston. For all the wrong reasons I can confirm an unrelieved bridge plus no holes is worth about 1/2 lap of the Elsinore GP.

iggys-amsoil wrote:I don't run the holes.

However the instructions say .300 from the bottom ring and holes to be .060-.090.

Dude, if you think 90 thou is big, look at Glens pistons...

Yep... heres some pics

http://www.bannedcr500riders.com/board/ ... c&start=27

fastkart wrote:Yep... heres some pics

http://www.bannedcr500riders.com/board/ ... g&start=27

M.F.D.B. wrote:

iggys-amsoil wrote:I don't run the holes.

However the instructions say .300 from the bottom ring and holes to be .060-.090.

Dude, if you think 90 thou is big, look at Glens pistons...

I saw those, and considering the application I see why. I still think its over kill, but I'm not even going to question the man.

iggys-amsoil wrote: I still think its over kill, but I'm not even going to question the man.

Better not!!

Ok, I get the idea behind the holes for exh bridge, but in Brit's pics, what are the rest of them intended for, mainly the large one?

4Z wrote:Ok, I get the idea behind the holes for exh bridge, but in Brit's pics, what are the rest of them intended for, mainly the large one?

The small holes are for the same purpose as the one on the bridge. To get more oil to the cylinder wall.

The big one, Glen told me, is basically an extra intake hole. I see it as a way to get more oil to the small end bearing. He told me if I didn't have that hole cut on a replacement top end, I'd lose some power.

oil.......

Intake.