Thank You Solace,1978 Aisin rebuilt by @FJ40Jim, for ‘78 FJ40, with factory electronic ignition, was night and day to what she was when I bought her.
Eventually, the oem dissy vac advance module developed a huge vacuum leak and I had an issue with the oem fuel pump diaphragm splitting and pumping fuel into the crankcase.
I bought a 2nd 1978 Aisin (from a MUD member) and sent it to @65swb45. Mark has come to Vegas for a wedding and we hiked and cruised together. He told me that he had learned some performance tricks that would make her run like an SBC.
I replaced the oem dissy, coil and igniter with a DUI and redesigned my fuel delivery system, eliminating the oem fuel pump and replacing it with two electric fuel pumps (One for each tank).
Once I installed the Aisin with Mark’s performance enhancements, she literally ran like she should have.
She started easily, easily cruised at 70... I passed at 75... once at 80. Once I found out all was good, I again kept my speed below 65.
I know nothing about other carbs... I do know Jim and Mark know their stuff.
I also know DUI, when installed as DUI recommends (timing @ ~12*BTDC, plugs gapped @ .050”-.055“ (I kept them at .050”), in concert with Mark’s performance enhancements gives more power and speed than a 40 rightfully needs.
Electric fuel pumps offer the security of never having fuel dumped in the crankcase and the inherent risks to engine intervals
Dual electric fuel pump provided me the security of knowing a pump failure would not shut me down... I just made sure I never kept less than 1/2 tank in each tank, minimum. I’ve been known to carry another 20gals on the roof rack.
So, this is my long winded way of saying there are experts on here that can make an Aisin carb hum. But, as @fireflyr inferred, above... you could be trying to fix an ignition issue, vacuum leakfuel delivery issue, etc., by tweaking your carb.
I am new to ih8mud and just purchased my first 78’ FJ43. Plagued with a variety of issues and Carb being the first to tackle. Fuel in the oil, fouled plugs, missing carb pieces, etc. not to mention multiple electrical ghost. The carb I have has been beaten and abused. Thanks for the direction.