What would cause this?

D

dunecj2a

Member

Feb 22, 2006

12

0

• Feb 2, 2009

• #1

I pulled my jug of to replace the tiny seal that goes on the end of the powervalve rod where it goes thru the cylinder. So I checked my piston and noticed the bottom ring was stuck and not moving freely. I pulled the piston off and noticed this weird wear on the grooves.
http://i357.photobucket.com/albums/oo18/tuc316613/Jan16wkend047.jpg

http://i357.photobucket.com/albums/oo18/tuc316613/Jan16wkend045.jpg

My powervalve was gummed up pretty bad and the rods on the side felt like they were stickin. Can this have been caused by that bad seal, it was pretty much apart and not doin anything.

 

T

TRexRacing

Member

Jul 23, 2002

440

0

• Feb 3, 2009

• #2

I believe that's the exhaust side of the piston?Got a photo of the dome?Is the dome pitted above the exhaust side?That piston appears pretty worn out and the play in the bore can cause rocking back and forth leading to wear at the top/bottom of the piston.What premix ratio/oil do you run?

 

D

dunecj2a

Member

Feb 22, 2006

12

0

• Feb 3, 2009

• Thread starter
• #3

The rest of the piston looks fine and there is no weird wear. It doesn't have more than 30 hours on it. I run 32:1 Yamalube.

 

whenfoxforks-ruled

Old MX Racer

~SPONSOR~

Oct 19, 2006

8,129

2

Merrillville,Indiana

• Feb 3, 2009

• #4

The ratio has nothing to do with it, at all! You need to have your bore checked. It could be out of round. Running loose tolerances will push the cylinder out of round. There is a lot of ring blow by. The wear patterns on the piston, and that dirt that got in there???

 

T

TRexRacing

Member

Jul 23, 2002

440

0

• Feb 4, 2009

• #5

The wear under the ring lands if abnormal.That portion of the piston is NOT supposed to be a thrust face.

 

J

jsantapau

Member

Nov 10, 2008

340

0

• Feb 4, 2009

• #6

where the rings catching the powervalve?

 

J

jason33

Member

Oct 21, 2006

655

0

• Feb 8, 2009

• #7

that black is oil blow by, the scuffs on the rings and piston ,are prolly from cold starts/not letting it warm up properly
check the piston to cyl clearance by the book
check ring end gap,by the book
hone it lightly-to seat new rings
get a wiseco piston ,and rings,there great products,always replace the wrist pin bearing while your in there ,its only 12 bucks i believe
break it in right and it will last!