So as usual I am doing things the hard way. Ordered a reed valve piston for the ct3 project after breaking mine being dumb and trying to break magneto nut binding the skirt with wooden hammer instead of going to the shop to get my tuning fork. Then upon inspection on piston arrival I realize it’s a 5 port cylinder with comparable piston and reed intake. PO said it ran but not so good and motor had bad mains. What’s the thoughts on a reed behind A piston port setup running ( just curious) and anybody got a 1st over ct1 piston to part with?
 

"....Then upon inspection on piston arrival I realize it’s a 5 port cylinder with comparable piston and reed intake...."

I don't understand.  You have a piston port (5 port) cylinder with a reed valve intake?  Then it's not a piston port...  or am I missing something?

The original piston is solid, no two holes on the back. The cylinder has 5 port holes in it and looking into the intake with carb attached looks like the reed valve unit. Let me look again and verify. Hazy memory here but without looking at another bike doesn’t the reed intake bolt to head with 4 bolts and piston port two? I’ll report back.

Without the windows the fifth transfer is isolated from the crankcase during scavenging. You may notice a slight loss of midrange power.

Here is what I found out-
My piston is a 1.25 marked so I was wrong on my piston choice.
The cylinder has 5 ports plus the opening in rear for the reed valve unit. I see the valve and it’s housed in the 4 bolt attached unit with the carburetor behind it.
So the bike did run according to a honest bike guy I got it from. He said it was down on power not running so well. So now I guess I’ll buy a 1.25 piston. I assume that will be aftermarket only.
SO looking on eBay looks like I have the 1.25 your trash my treasure MC piston was installed in the bike. I broke the skirt. eBay 362334873453. This piston is piston port no holes. What’s my chances of cutting my own holes with Dremel etc and being successful? I have a new .25 over piston to use as a guide. 

I'd be worried about cutting holes to match the correct piston as they're likely cast in such a way as to give extra strength around the area of the holes. Could cut 'one' central hole high up on the skirt to help the rear transfer thingy.

Seems i remember on the old forum people cutting holes in pistons. With Japanese industry of the time I can't see them designing a new piston for the reed ports. I bet they used the same mold for both and modified it. Also that piston is constantly against the cylinder wall supported. Maybe someone will join that has modified one. Recently mark posted about dvm cutting the skirt on one. I dont think I have many options on a 1.25 over. The one central hole seems easier but you lose the middle web which could add some strength. I have a .25 pp and reed piston ill examine closely for differences.

I absolutely DO NOT recommend cutting holes in piston skirt!    Skirt will very likely break off while running.

Trimming the length of a skirt (ala DVM's Blaster piston recommendation) is not the same thing! 

Blaster piston might work (see DVM's post) but clearance is important...  you might get lucky. 

Seems I need a 67.25 mm piston if 66 is standard and I'm at 1.25. I looked at the oem .25 over and looks to be a little more meat at the holes, not a lot but the vertical groove stops and piston thickens at the holes. Are there any options to run piston port with an adapter or something? I hate to not utilize the fresh 1.25 bore.  Does the blaster come in 1.25 reed or is there a decent way to run this cylinder with a piston port piston, maybe some sort of conversion of the 4 hole reed setup to spigot or something. I have some other bikes reed and piston port parts.can you link me to the post mark?

yamaha-enduros.com/index.php/forums/gene...-175-a-barrel#159184

See above for recent post from DVM

A new piston, even if same brand, etc. might have a different clearance in the bore. That's why when you send a twin to a reputable shop for boring oversize you'll get the pistons and cylinders back marked "1" and "2" or some other indication of which piston goes in which bore... even two "identical" new pistons often require slightly different final bore sizes to get the clearance just right.