My 77 CJ7 has run for years without any attention, not that I put any great miles on it. This summer it decided it was going to be difficult, so now I have to remember how a carb works, with very small success.
I took it all apart and cleaned it, and blew out the jets. Put it all back together and tried it, no dice. When I come off of throttle, it dies unless I very carefully feather it down to idle. I’m clueless about what’s wrong, and have run out of dead chickens to wave over the necromantic device.
I think it would be less trouble to pull the engine and put in a spare 4.0L I have on the shelf.
I had a pinhole leak in the diaphragm of one of my two Mikuni carb, and my twin cyl bike would act really weird.
In that case, it wouldn’t evenly provide power with throttle, but just as telling was when I got going and suddenly let the throttle go, the engine would die.
Point is, look at your rubber, old stuff gets destroyed by ethanol, mileage irrelevant.