Looks like one of those Mitaka pistons. 

Haha, that'll stir thing up.

RE: RT325's comment on DT360 piston BS
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 Yes, I'd say he's B.S.ing
First of all, that's not a 72~ 74 RT or DT360 reed piston that was destroyed, as they all had a Dykes style top ring.
I'm curious what piston it is though . . . might be a RT1 piston that someone drilled holes in .... that would make more sense to me .... and would likely break, as they didn't have reinforcement cast into their design. 

If Yamaha put "more" silicon in their racing pistons, that's news to me.  As far as I know, the reason for higher silicon content is mostly to reduce the rate of expansion ... if anything, higher silicon content makes a piston more brittle. 
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Thanks for commenting Enduronut. I knew you'd be 'onto it'.
Now i go back & look i can't find where it said 'that', so maybe someone said it on here on another post, not the facebook blown motor page.
So looks like it's me talking rubbish again.

Useless trivia alert...  Back in the 1970's when these bikes were new, I read a book or an article that said the "big four" in Japan (Yamaha, Kawasaki, etc) were using pistons in their standard production machines with silicon content levels that were considered "race only" in the rest of the world.  They marveled at the effort since apparently doing so wears out the cutting tools used to machine the pistons very quickly.

Here are Enduronut's "failed cheap piston pics".  I will try to get them to show up back in post #11

Thanks MarkT that shows you should use quality pistons

Found the facebook--answers--in relation to the blown 360 piston.
I'll direct this to Enduronut with refference to what i said earlier--silicone content "which i said wrong".
Looks like the comment was higher Alloy Content not silicone--so is the opposite to what i said.
Comment down the right side there.
Just interested to hear your knowledgable take on it all. Cheers.

www.facebook.com/photo.php?fbid=70171307...7130718306197&type=3

I have fitted many DT175MX pistons to TY175 motors, and they work perfectly. Numerous eBay sellers, also list them to fit TY175.

Hyper-eutectic alloys are commonly used in almost all present day pistons, which means that a modern forged piston, can have a bore clearance which is tighter than earlier pistons.

A bespoke piston manufacturer I know in the UK, who makes forged pistons, buys his forgings from a company in the US, that also manufactures forgings for Wiseco, using custom tooling he made himself.

Very clever guy, is able to make pistons from billet aluminium, and has even made some special application race pistons, from magnesium.

His pistons are works of art, and he is probably one of the few people in the world, who can still make one offs, and small batches of custom parts.

I will see if I can find a pic of one..................