Judging by the photos replacing the cylinder together with a new piston and rings seems the best course - depending on what the rest of the engine looks like.

That's pretty ugly. I'd see what sort of oversized pistons are available and if they are big enough to clean up the damage.

That looks a bugga don't it. Looks like somebody has (badly) honed the barrel with all those scratches in it. Has a circlip caused those gouges or a broken ring?

You said:
"The gouge was about half a cm deep maybe 1 cm I didn’t measure,"

half cm is like 3/16". Did you mean 0.5mm? Like (20thou) 0.020"

Best get it measured properly to see if an overbore will clean it up.

This looks dodgy:
Piston kits for £25 on ebay, I guess they are Chinese, has anybody tried them? I paid that for a set of oem rings.

Trying to clean up that damaged cylinder bore and fit an oversize piston to it would be expensive to say the least, even if it could be done and he uses Chinese parts. It'll be interesting following this project as he decides on his course of action.

My best guess at this point is a replacement cylinder with a new piston and rings. Chinese manufacturers are making engines and transmissions for major bike producers like Yamaha and Honda. So cost wise it seems smart to go with Chinese engine parts from a top line manufacturer.

We'll see soon enough what he decides..

Not had an engine re-bored since the early 70's can't remember what it cost then, is it pricey nowadays. I would have thought cheaper than a new barrel. Mebbe Chinese parts/engine is the cheapest way forward.

I was surprised when I stripped my engine to find the bore was fine so I got away with just new rings.

Need to find the cause so it don't happen again.

No idea what re-boring costs anymore. Used to be common back in the day. Some still go that route. Like you though it's been a lot of years since I knew anyone who had an engine re-bored, motorcycle or otherwise. My mechanic uncle, WAY back in the day, re-bored and re-built a lot of old automobile engines, bringing them back to full serviceability. Seems there's less and less call for that as far as most are concerned these days.

You may be able to have it rebored.

$100 plus freight
https://precisioncycleinc.com/services/o...-pricing-sheet/

Another option in Wisconsin - they may do the XT225 as well
https://www.usnicom.com/Yamaha/DirtbikeCylinderServices

Finally a low-cost but SLOW method - go talk to a local community college or tech/trade school. I know back in my university days all sorts of project bikes and cars were run through the school''s machine shop. many times the students are required to demonstrate proficiency on various machines and need a suitable project.

You supply the parts, pizza, Coffeys, etc. and you get the job done.

JP

I have had this happen twice. 2005 XT225 with 18K miles, wrist pin worked past circlip and scored bore. Had it re-sleeved, bored and honed to fit OEM piston. Total cost $400 with my labor. 5K miles later same thing! Still in pieces.

Bought 2005 XT #2 in July of 2017 with 13,450 miles. Pulled engine apart this winter to reseal top end and there was still crosshatching in the bore at 30,774 miles. Good to go.

On another forum I was on yesterday, mention was made of two XT225s with “wrist pin problems.” Anyone else here with similar experiences?

OEM standard size and two O.S. piston kits are available for 1st gen XTs. The earlier XTs didn’t have Nikasil-coated bores.

Hope this helps.

That is strange, I wonder how the pin could get past the circlip? Unless the circlip was the wrong size?

It’s a mystery to me. All OEM parts used. Bent rod possible?