What's this barrel?

[Nathan S]

Now, before you all say "That's just a YZ125F barrel you twit!", have a closer look - particularly at the lack of visible steel liner.

The head is marked 2X3 (YZ125F), but the barrel is 2Y5. I've got NFI what a 2Y5 is, and it doesn't return any matches on Speed and Sport.

[cyclegod]

2X3 = 2Y5 which is YZ125F that was the prefix on both barrels I had on mine in NZ. In a yamaha hand book i once had it listed every detail difference between the YZ100/125E and YZ100/125F and it included details that indicated certain countries got 2X3 and others 2Y5.

[Freakshow]

is the bore coated ?

[Nathan S]

It appears to be a chrome or nicasil type bore, which is the interesting bit.

[holeshot buddy]

a lot of factory barrels were plated 
could be never know

[TC91]

It looks a lot like the optional factory barrel. Chrome bore, slightly different port timings. I have one and had it on my  YZ125F in '79 and can recall a marked difference when we swapped to the factory barrel.Not huge but enough.

[Nathan S]

Ah, so that pretty much answers the second part of my question.

Thanks all.