Should I Reuse Piston in Rebuild

SouthCarolina1

Petty Officer 2nd Class
Joined
Jun 17, 2013
Messages
165
I have a 1989 115hp 2-stroke Yamaha that I am rebuilding. One cylinder had 50 psi and the other three were at 128-130 psi. The block and camshaft are at a shop being cleaned and inspected. I am prepping the other parts for re-assembly and I ran into a snag. One of the piston heads that had good compression, has two batches of light scoring but none on the sleeve. Would you just clean it up and reuse the piston OR should I get another one (would buy another used one off of ebay). Assuming cylinder doesnt need to be bored. See pictures
 

Attachments

  • photo265744.JPG
    photo265744.JPG
    29.9 KB · Views: 0
  • photo265745.JPG
    photo265745.JPG
    24.8 KB · Views: 0
  • photo265746.JPG
    photo265746.JPG
    24.5 KB · Views: 0
  • photo265747.JPG
    photo265747.JPG
    27.8 KB · Views: 0
  • photo265748.JPG
    photo265748.JPG
    29.5 KB · Views: 0
  • photo265749.JPG
    photo265749.JPG
    32.8 KB · Views: 0
  • photo265750.JPG
    photo265750.JPG
    33.2 KB · Views: 0
  • photo265751.JPG
    photo265751.JPG
    32 KB · Views: 0

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Looks pretty darn good to me...maybe a Scothbrite pad to remove those scuff marks and re-use it, as long as it measures O.K. for clearance with cylinder.....There should be a clearance specification in your book in thousands of an inch between piston outside diameter and cylinder inside diameter.
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
Camshafts? This is a 2 cycle isn't it. Did you mean crankshaft? :noidea:

I also don't see any need for new pistons. But that really depends on the bore. If the bore is okay, new rings and gaskets and reassembly it. JMHO
 

SouthCarolina1

Petty Officer 2nd Class
Joined
Jun 17, 2013
Messages
165
GM280 thanks for correcting me. I meant to say crankshaft. I have the Yamaha service manual for the motor and I'm waiting on the tool for measuring the outside diameter to arrive. Ill let yal know the results.
 

SouthCarolina1

Petty Officer 2nd Class
Joined
Jun 17, 2013
Messages
165
Piston sleeves miked within tolerance but two of the four piston heads were below tolerance. It was the two pistons with scoring. One was right on the line and one was .001 under tolderance. So I am replacing both.
 
Top