I have the original Mikuni carburetor on my Mitsubishi Astron G54B engine, the vehicle being a 1984 Chrysler Executive (Chrysler K series); Lately, once every week or so, the car will start having trouble running, and eventually cease. I was able to quickly figure out the issue is the intake flap in the carburetor, (a razor blade shaped/sized door that rotates to close/open for air pressure) seems to keep (getting stuck?) in the fully open position, accepting excess air causing the engine to "suffocate" from excess air. I'm still learning, so apologies for not naming this specific component correctly, but, basically, I push it closed and release to let it open again a few times (it appears to be spring loaded, causing its default position to be wide open, or maybe it's just stuck like that) and the car starts fine, and stops having issues (for a week or so).
How do I fix that? Do I just basically need to rebuild the carburetor at this point? I would love to, I just need to find aid in doing so, I hear these are pretty challenging to work on compared to traditional carburetors.
Following up on this, for others learning these Mikuni carbs and having a similar experience;
Turns out, in my specific case, my carb is fine, the issue is vapor lock. I live where it gets extremely hot, and this only occurs when my engine temperature reaches a bit above operating for a decent amount of time. The fuel pump/filter/etc is all mechanical and located right next to the carb, right on top of the engine, so it's going to get basically as hot as the engine if not more, and vapor lock before you can say "noooo".
After some studying, how that intake flap works on these specific carbs, is, they open up based on temperature. The hotter it is, the wider it will open, so mine is not stuck at all, and operating correctly. I got to learn this the hard way today after not being able to start no matter what I did, and after speaking with a local old school mechanic, he agreed it is vapor lock.
So I'm going to research on upgrading my fuel system to stop this issue.
Thank you to everyone contributing and reading!
I'll tell you what I do. Those carbs aren't that good. I take the car by throw it away and I try to find a conversion kit like a Weber. They work a lot better and that thing's so old Jenny. They don't have to have any kind of emissions testing anymore
That might be a good idea, I'll see if I can find a different, reliable carb, maybe only pop on the original when it comes time for yearly smog (since where I am you're disallowed to drive more than 5000 miles a year unless you smog), and I daily drive this car