If you're running pump gas, the life span is only about 5-6 months. If you had not treated your gas and then run the engine long enough to get that treated gas up into the carb, you could have varnish built up in the carb ports. Another issue could be an accel pump rubber breakdown with the added ethenal required now days. Either way I'd be doing a super clean and rekit with updated rubber parts. HAVE FUN RACIN' !!!