I´m just completing a complete 71 cb350 rebuild. It´s a good bike to do because you can actually still get a lot of the parts from honda. My dealership has been really good at getting rings and gasket kits and almost everything else except for pistons. I had to recondition the ones I had. Fortunatly I also had a bike in a basket as well so that helped a lot. As for the carbs and the valve on the tank you should take all that down to the bare parts and clean it all thouroughly. If it had leaded gas in back then then it will be full of white lead and if the last gas in it was unleaded then it will be all gunked up with varnish. Either way 25 years of no running will not have been nice to those carbs. Mine was siezed so I had to get down and dirty with the whole bike and I did a 100% part resto. That´s a lot of work but you would not believe the little things I found that needed attention until I inspected them. All in all though I have kept the cash outlay under the $800.00 mark. That´s what I paid for mine when I bought it brand new back in 1971. Wish you all the best with yours. It´s a great bike and if you take care of it you will still be riding it another 25 years from now. I have 120,000 miles on mine. That´s a lot for any small bike.