have you checked the coil and plug connections .you may have disturbed something. i recall after doing some work on my kv6 that i fitted the plug leads according to their length on the bank nearest to the rad. plug 1 left and plug 3 middle were wrong way round according to their respective lengths. this has been noticed many times and was a production issue so im told. i just swopped them over after scratching my head for hours and ... bingo !! all good. worth a mention to check yours ....