I'd agree with that guy, maybe time to strip down and check the carbs.
Make sure theres no build up of crap.
Get a new seals, remove the float chambers and check your diaphragms,
they may be starting to perish...thats just a maybe though.
Im pretty sure you can buy a new top yolk/fitting for pre-existing top yolk, that enables you to fit flat bars, that'd help for a better riding postion. I was looking to fit a thundercat front end to my '90 FZR600 that im rebuilding for that reason. Easyer to get parts and the flat bar would be better for what im planning.
http://www.jesterstrickbits.co.uk/acatalog/Yamaha_YZF600_Thundercat.html#aABM_2dTY_2dTCAT
cheers
Hay Tony,
New to the site and was just browzing, you still have the bike?
I have the same bike but mine was in a bad smash, wondering if you'd be interested in breaking the bike?
cheers