Hi there, & welcome to the madhouse. I see that you're from Great Britain. Whereabouts exactly, because that description fits England, Scotland, Wales & Northern Ireland. Are you a Paddy, Jock, Taffy or an Englishman. :whistle: :roll:
BTW, you asked if you needed to change the front sprocket at the same time as the chain. Check the sprocket for wear. If it's not worn, then there's no need to replace it. The same goes for the chain. Check it, & make sure what condition it's in. It's more than likely that all that's required is a good clean & lube (plus setting to the correct tension). :2tup:
There are quite a few GZ125s, here on the island. Most of our speed limits are 50kmh (30MPH) so they're quite adequate for the job. Don't know anyone, personally, who's got one, so I don't know about parts being the same as the 250.
