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

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.

 

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.

 

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

 

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.

 

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...

 

Still search piston for this engine... I don`t found yet. or something similar.Anybody has an ideea what shoud i do ?

 

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..

 

Hi IONUTFG,
Did you resolve your piston problem? If not please let me know - I may be able to help.