stick or change

I have a 2000 fc501 which is road registered i love the thing to bits it puts a big grin on my face every time i get on it.I think ive got it as good as iam gonna get might go for a 15 tooth front sprocket cos it has the 6 speed box and you can be quite busy changing up and down.The million dollar question is do i get a more modern berg and will i gain anything over my 501.I kept my xr600 just in case i didnt get on with my berg but now the xr seems to be as heavy as a tractor.My plan is to sell both and buy newer?.i might just be paranoid because i dont now how mine was maintained before i brought it but everything seems fine but i could have the same problem if i buy another anyway great site info on forks was great learnt a lot
Cheers Ade

Cheers for that iam off to france in the lot in about 7 weeks taking the berg with me so i had get a move on if i want to change.I will put the xr up for sale first will have to get mot etc and see how i go from there
Cheers Ade