Hi, try this google photos link I just made.

It would send that either. I try your method.


 

ok, heres the first one

Hi RT, cant send any pictures even with your Imgur thang. I get back to UK in a few days and will do some measurements.
To sum up:
66mm bore
Fits long stud bottom end.
NO boost port on intake. 
6 fins (with miss alined cuttaways in each one)
DT175 reed cage is too deep and wont fit in.
N.S stamped on bottom left. No other numbers anywhere.

I do it from my desktop computer but tried it on my phone & I'm lost. I'll carry on & try to master it. I know everyone does  everything on their phone these days so I should learn. photos.app.goo.gl/CE4UsV8bkkkDFddP6 yay I got it to work, but now I don't know how I did it. I'll try again.photos.app.goo.gl/9LLMW1QQDUBNppwz8 Yay, i did it twice after many fails but still don't know how. From my phone that is. Can do it on the desktop almost with my eyes shut.

From what you're describing and a text message I received from an expert who doesn't post here much, you have an aftermaket Noguchi cylinder.  It should have a chrome bore. 

I have one in a box someplace.  I'm pretty sure if you wanted to use it you'd need to have it re-chromed as I'm pretty sure the rings they used were special and NLA...  standard Yamaha chrome rings will strip the original chrome very quick and might ruin the cylinder.

Chrome bores usually run cast iron rings with a high manganese content.  As Mark T says.  Standard chrome faced rings should NEVER be used in a chrome bore.

It can be difficult telling standard spun cast iron liners and chrome liners apart.  Something that Perkins liked to do was sometimes fit chrome liners and sometimes cast liners to the same family of engines, depending on application.

It can be hard to tell the difference... 
Engine shop trick.. Rub a little copper sulphate solution on the cylinder wall. 

If it turns copper coloured, it is cast iron.

If there is no change, it is chrome.

Shouldn't be that hard to tell because if I remember correctly it should be a solid aluminum casting with a plated bore...  no iron sleeve at all.

Modern "chrome" plating (Nikasil aka Nicom) of the aluminum cylinder can actually use chrome rings... at least the Wiseco chrome rings work well in my experience.  "Old school" chrome bore plating definitely cannot use chrome rings.  But always best to double check with the plating company on ring compatibility. 

Yamaha did supply a cast iron ring option for some models so that could be an avenue as well. 

 

Yes as Mark says, on yamaha cylinders just chrome on aluminum. & I finished off my worn out GYT cylinder 20 years after I stopped using it by giving it one more try but shuffled the old rings around looking for what I thought was ok & being aware the correct material ring was needed BUT I MUCKED UP, ripped it to shreds in a minute. Before that it was worn at the ex port etc & rattled bad with extra clearance but still went like he'll & they hold there performance right till the end of the race & don't lose their edge as can dissipate heat quickly where my cast bore cylinders always seem to loose the crisp edge before the race ends on a hot day in comparison. Maybe my cast bores are just worn out thou lol.

Cheers gents, I would appear Mark T nailed it. I have a Noguchi 175cc barrel and just found 2 brand new 66mm Noguchi  pistons with matching rings here in UK. Plus a Noguchi reed cage. I will have to have the barrel relined/coated just make sure and may need a reed cage spacer and check the piston clearance in the head. (I've seen mention of a "barrel spacer" ) Mystery solved. 

Thanks for the update!  Great news, if you have the Noguchi piston/rings you should be able to run it if the chrome is still decent. 

Let us know how it runs...  they are pretty rare aftermarket performance parts.