idle it for a minute (on a level surface) then pull the rods/top & the fuel needs to b at the notches in the float baffles on each side. I think the dry float setting is 7/16". Need a .098" or richer pri jet(s) in there and I'm assuming this stumble is when warmed up/part throttle & if happening during warm up in addition the elec choke can come off way too fast causing a lean stumble and hurting your gas mileage if that is imp. If richening it helps the part throttle bog then concentrate on dialing in the "cruise" step & might note what springs are in there and can run a vac gauge out & taped to the windshield to find when the bog is. Get a baseline on all the details