Quick question for the forum... Im putting a fully fresh motor back together for my 1974 DT100a restoration project. I hadn't touched any of the motor parts for several months, this weekend I built up the bottom end. Moving on to top end I see the Wiseco piston the machine shop supplied me with(and bored my cylinder to) does not have an intake window?! I seem to recall reed intake motors always having the window/s in the intake skirt. The box says DT100, MX100, LT100 ALL. Googling the part number turns up Dt100. Any ideas? Thanks!

Not all reed motors had windows.  Stock piston did if I remember correctly.

Does the Wiseco have a high cutaway in the intake skirt?  Yamaha MX models sometimes used that instead of windows. That's my guess.  I'm also guessing it might be an older NOS Wiseco?  I think I used a newer one a couple years ago and I remember it had windows...  it was the type that had what looked like "computer etched numbers" on the crown. 
 

Does it look like this wiseco 52mm DT100 kit? on ebay. I can't link ebay but auction number is EBay item number:175432551006.Wiseco Piston Standard Bore 52mm 235M05200 Yamaha DT100 LT2 100 MX100
Was going to say yes they all have holes--until i read Marks coments which is right of course.
photos.app.goo.gl/R99bJhUPPsT5Cag1A

Thanks for the replies guys. It definitely looks like a brand new current Wiseco piston. It has the computer etched numbers on crown like you say. The box says ‘235M05300. For dt100 mx100 all years.’Also says ‘replaces 235p4’. The skirt appears uniform on o take and exhaust. 
Guess I could try and email Wiseco. This project has really been fighting me the whole way lol. 
Also, curious if we lost some threads on the forum? I had started a restoration thread last year but can no longer find it anywhere. 

"Also, curious if we lost some threads on the forum? I had started a restoration thread last year but can no longer find it anywhere." 

Yes, some data has been archived.

Have a word with MarkT if you'd like it reinstated.

Ok the number i randomly found was for a Std size 52mm.
Your number is 53mm. 1mm oversize.
You say piston looks uniform on both sides, so the plot thickens.
I'm thinking it should have the big cutaway as in my link. If it doesn't have holes or cutaway it'll still run but not perform as it should.
Getting interesting--or i'm misunderstanding things.

Ok I emailed Wiseco. Wish I could post a pic for you guys. I’ll try and host a pic and link it. 
Boy what a bummer! The machine shop does great work, but if I’m out almost $300 and the time to paint the cylinder etc that really sucks. 

Found a pic of a Wiseco piston kit advertised by a powersports shop in the US for DT100 all models and years.  1mm over.  That is the intake side.



 

It's interesting you keep saying "the box says"...  I wonder what the actual piston says on it?

In any case, we put a non-windowed piston out of necessity many years ago (only thing available locally before ebay or the Internet) in a friend's CT2 and it ran fine. 

Same photo & number as in my pic link in post #3 Tinkicker.
So if OP tells us the number on top it might confirm what we need to know. Then again, we love pics--if pos.