How can I tell if my piston is cast or forged?

[pitbulloncrack]

Took the top end apart to inspect it today and I need some verification on a couple things.

First - How can I tell if this piston is an OEM cast piston or a forged aftermarket?

Second - The number on the top is 50. Can someone verify the bore size?

Thanks in advance!

 

[xJust_Causex]

Im gonna guess it is forged, and the 50 means that it is .50" over stock bore.

 

[pitbulloncrack]

Im gonna guess it is forged, and the 50 means that it is .50" over stock bore.

So does that equate to a 66.5 bore? Is there a way to tell for certain if its cast or forged? I'm asking because I'm gonna throw some new rings in and I don't want to buy these here, if I need to buy these here?

 

[pitbulloncrack]

Bump for a definitive answer on this, thanks!

 

[brandoz28]

a cast piston will have a much rougher finish on the top and underneath usually. but it can be hard to judge if its coming out of a motor that's eaten itself alive

 

[Jay]

your piston you have now is 66.50 that is what the .50 on the top of the piston means.For the piston as Brandoz28 said it maybe cast stock over bore.

 

[98blaster+4]

if you post up the other numbers someone will chime in, wildcard helped me to find out that mine was a wsm piston, he knows his chit man.

 

[pitbulloncrack]

I couldn't find any other numbers on it, that is why I was confused. I have only run Wiseco in my KX and other bikes so I am familiar with those. I guess what I need to know is what is the difference between This says "DOES NOT FIT Wiseco Or Other Forged Pistons" and this. Will the Wiseco work with any piston? When I tore the top end apart, the piston and cylinder looked really good so I just want to replace the rings to get me through the first part of the summer. I plan on doing a complete rebuild at the end of the season.

 

[stephen12091985]

just post up a pic of the piston

 

[hotrodaj_2]

The cylinder clearence for a forged piston is more than a cast piston. Forged is a better piston but it swells a little bit more. If forged swells more it must change the ring groove a little bit more also imo. I'm not sure but maybe that is the difference in the rings.

 

[royalt67]

Wiseco puts the entire part # on top of the piston. They also use a differently shaped ring that doesn't typically fit other pistons.

So, it sounds like you have a non-wiseco, probably cast piston. (Not many manufacturers make forged for blasters, wiseco and JE being the only I can think of offhand) Get the rings for a "stock-type" piston, like the Namuras you had a link to.

 

[royalt67]

...and like Jay said, you prob have a .50mm over piston, but it would be worth your time to have your bore and/or piston measured to be sure. Any decent shop should do this for free if you don't have the tools.

 

[125pb]

hay sorry to but in on this post but i have a similer question. my piston says 4275 on the top and then 573m06650 in the middle just above the little arrow. what does this mean?? can you tell what brand it is by the part#??

 

[hotrodaj_2]

Just to answer one thing on this thread, Wossner brand pistons are also forged. I' m learning that they are the only BB piston that is forged anymore. Not sure if they make standard bore sizes.

 

[BustedassYZ]

Dose it say ART on it anywhere? That would mean its a PROX or an OEM If it dose