Hi Mike,
Jim here. I had a Berg 400 FE on a 53 plate which was a dream to have. I went from a XR 250 kick start to her and what a fantastic bike. I bought it new from NTB in York and had it for 3 years and leart to ride on it. It started first time every time and the only problem i had was with the lights but my new Husky has lost it lights also. Nothing that could'nt be mended with a screw driver and some electric no how. The main problem with the Berg's was the electric start. I was advised to always take the starter cover off on the right hand side of the engine after power washing and to dry it out with a cloth then spray with WD40and put back together. 3 alam key screws a 5 min job. My mate had a 501 Berg and he was crap with cleaning it and towards the end of 2 years had nothing but problems with trying to start it were i did not. As a bike they are great and a lot cheaper than KTm's. you can still get parts for them and if you ring NTB in York they sometimes have some good Bergs in second hand.
In Summer we put super moto wheels on them and gave thenm some real hammer so you can try and kill them but you'll struggle. I think the old reliability comes down to poor maintenance as i had no problems and would still have it today if it wasn't for the Wedding.
Not sure of the new ones yet as i went to Husky as NTB started stocking them and i got it at a good price. I know 2 years ago when the old range of FE were being changed to the new i did have a 450 FE on order but the dealer let me down. Hence the Husky.
Bergs, Good bikes for good money.
Hope this helps
Jim