Am i due a top end overhaul?

[Arj256]

Was investigating the source of my blowing exhaust, thus taking off the exhaust. Looks like a new gasket and a little bit of welding should sort that.
Whilst the exhaust was off I had a look inside the bore and noticed there is quite alot of scraping marks on the piston and some on the bore itself.
What is the normal mileage the piston should be changed at?
Looks quite worn to me?

Pictures:
Piston skirt: http://i2.photobucket.com/albums/y29/ar ... nSkirt.jpg
Piston rings: http://i2.photobucket.com/albums/y29/ar ... eRings.jpg
Inside of the bore: http://i2.photobucket.com/albums/y29/ar ... heBore.jpg

The bike seemed to pull quite well when I took it out, but wasn't smooth off throttle which i was putting down to the exhaust leaking.
Also looking at the front brake lever, is this cut out normal behind the plunger for the master cylinder?

http://i2.photobucket.com/albums/y29/ar ... eLever.jpg

Thanks

[back off road]

not pretty bore and piston wise , but the front brake is ok

[knackeredMk1]

The bore si not good and a rebore, piston and small end bearing would be worth it. This wouldn't effect off throttle performance too much. Probably the jetting isn't quite right.

Piston milage is a 'How long is a peice of string?' question. Depends on all kinds of things. 10 miles to over 20,000.

The front brake has an external dust seal split. Won't generally effect perfomance but will cause the internals to wear faster.

[Arj256]

Where are the recommended places to send the cylinder away for a rebore? Also along with replacement piston etc?
The places that are mentioned in the "Manuals and Parts" be the best place for spares?
Does look prudent to sort it out now whilst going through the bike.

Ah have seen the dust seal in a picture on e bay so know what bit that is, have one on the clutch side thinking about it.
That's reassuring, didn't look to be any fracture marks there.