You can start just by looking at how hard it is to remove the carbs for a cleaning. I know had a Sabre....same design. My friend just picked up one of them Sabres.....I looked again just for old times sake.
His runs but not that well. Will be sitting for a few days with carbs full of Seafoam just in case that works and we don't have to remove them.
If you are crafty and like working in tight places with bent tools, you may be able to do as we did. Remove one of the bottom carb covers and inspect,left rear was the easier one. Then assess the amount of crap that may be in there. That one wasn't too bad....no grits so we are trying the Seafoam, just in case that works. I hope we get the "Miracle in that can". Phew....will know next Tuesday.