Piston for Yamaha 5bs 661 5hp 2 stroke 1970 ?

Discussion in 'Outboards' started by ionutfg, Mar 20, 2020.

  1. ionutfg
    Joined: Mar 2020
    Posts: 4
    Likes: 0, Points: 1
    Location: Romania

    ionutfg New Member

    Hi ! I purchased recently an yamaha 5bs 661 5 horsepower 2 stroke from i don`t know maybe 1976 year? When i disasambly to reconditioning the engine i found an cracked piston with a missing part between piston rings...Inside the piston it`s marked YAMAHA IZUMI 5 and on top it`s 510 K 97..Can somebody help me with the factory piston code ?? I found on internet some pistons look identical but i don`t know.
     

    Attached Files:

  2. kapnD
    Joined: Jan 2003
    Posts: 623
    Likes: 69, Points: 28, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    You need to verify that the cylinder is within specs to accept a new piston.
    If not the cylinder will need to be bored, and an oversized piston fitted.
     
  3. ionutfg
    Joined: Mar 2020
    Posts: 4
    Likes: 0, Points: 1
    Location: Romania

    ionutfg New Member

    the cylinder is ok.Probably was changed and when found cracked piston he put all toghether and sell the engine... I will atach more photos
     
  4. gonzo
    Joined: Aug 2002
    Posts: 14,150
    Likes: 540, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    I would look inside the crankcase very carefully for the missing piece. It is possible to break a ring landing by improperly installing the piston.
     
  5. ionutfg
    Joined: Mar 2020
    Posts: 4
    Likes: 0, Points: 1
    Location: Romania

    ionutfg New Member

    I`ve checked inside the crankcase and the missing piece of piston it doesn`t exist.I called the last owner and he sayd he changed the cylinder and the head.So now i had an engine with good crankshaft,good cylinder and head but with the broken piston.Practicaly he put the broken piston inside the engine only to start and sell the engine...
     
  6. ionutfg
    Joined: Mar 2020
    Posts: 4
    Likes: 0, Points: 1
    Location: Romania

    ionutfg New Member

    Still search piston for this engine... I don`t found yet. or something similar.Anybody has an ideea what shoud i do ?
     
  7. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,385
    Likes: 454, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    You could always attempt a "bodgie" repair by taking it to a machine shop, and welding some new metal on, and turning it down on a lathe, but it may not take properly, on the cast alloy. Only one way to find out, other than that, you need to order another one, and if not available new, try outboard wreckers online..
     

  8. ian73
    Joined: Apr 2020
    Posts: 1
    Likes: 0, Points: 1
    Location: uk

    ian73 New Member

    Hi IONUTFG,
    Did you resolve your piston problem? If not please let me know - I may be able to help.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.