I have had this sweet little bike for a couple of years. I've done a few things, water pump and all bearings, fixed the fan motor, new shock, new fork seals, new shoes. 

She runs nice and starts pretty easy. I'm a beginner, so probably not too fussy.

I have no idea about the history. When do I consider a top end? Based on the age, I will guess that will include cylinder plating and bottom end bearings too. I don't want to wait until it's too bad that I can't fix it.

TIA!

Leave it alone if it’s quiet and running fine there not like mx bikes that need regular rebuilds 

Rattle = fix

No rattle = carry on as normal

I wouldn't bother until it has such little compression it doesn't run and sounds like a bag of spanners lol. Check your thermostat is working regularly thow got my rev 3 out today and the thermostat is dead.was working fine when I put it away a month or so ago. 

A set of rings will restore some zip if it’s lacking or hard to start but these chrome bore cylinders don’t wear like the old bikes. If you’re happy with the power and it’s happily humming along it’s fine to just keep riding.

18 hours ago, Creepytheclutchmaster said:

Check your thermostat is working regularly thow got my rev 3 out today and the thermostat is dead.was working fine when I put it away a month or so ago. 

Mine was not working so I direct wired it.

3 hours ago, dan williams said:

A set of rings will restore some zip if it’s lacking or hard to start but these chrome bore cylinders don’t wear like the old bikes. If you’re happy with the power and it’s happily humming along it’s fine to just keep riding.

Well, so far so good then! Do I need to measure my cylinder to know which rings to get? (A-B-C pistons, etc) - Or is it just one size for rings?

This is the parts list. Only one ring size.

https://betausa.com/content/SUPPORT_PDF's/2005 Rev 125-200 2 stroke.pdf