My 1992 MiniCab U42T has been bogging after warming up, and on cold starts missing. - I still have some work to do to the carb, due to no fast idle, I took out the NGK iridium spark plugs (once again) blasted them clean, and reduced the gap from 37, to 35 thousandths. - It really seems to have woken it up. - It seems like a really small adjustment, but it seems to have improved it a lot.
Not positive on these rigs since I have fuel injection but typically on a thermal/mechanical connection you follow the mechanism attached to the choke plate / carb and follow it back to its source. That being said I'm not convinced your problem is due to choke issues since you also mentioned you have ' cold start missing " To do a quick check / eliminate choke issues, let it warm up and once it starts running rough you can probably manually control the choke plate to see if the symptoms change . Chasing spark plug gaps and issues is usually a dead end when it comes to performance / engine running issues.... Call me crazy but in all my years of diagnosing and fixing small engines, its never been the spark plug..... And if the plug is bad, its usually due to something else causing it to go bad ( oil in cylinder / fouling out / overheating / and so on ) Help with diagnosing : Remember you need fuel/air/spark/and compression for an engine to run good. >> Does the problem consistently happen? >> When the engine is bogging down, does it happen at idle or when you are accelerating ? >> When the engine bogs down, spray some carb cleaned into the intake and see if your symptoms change. No change? Then its most likely not a fuel / air issue. Runs smoother? Then you have a fuel / air issue >> Check your air filter , make sure its all clean and not loaded with dead mice and debris >>> Check your plugs wires / distributor / and all of that to make sure connections are secure *** I just had a runs rough / no start issues and when looking at the distributor cap in the dark, I could see the wire was grounding out causing my problem . >> Sounds like you managed to pull your spark plugs , so your halfway to a compression test. You may need to get that done if you cant solve the problems otherwise. Chances are you have something fuel / air related causing the problem, maybe even just a dirty carb. Some people may laugh at this, but one of the best tools I used at my shop can be seen below, you'd be surprised how often it has solved run rough problems on small engines >>https://www.homedepot.com/p/Mechani...ntain-Protect-All-Engines-MIB-016-1/326761792
^ long story short like I said, check the thermal choke actuator to possibly eliminate your warm issue. Maybe it’s stuck halfway and causing cold hard start and a bog when warm.
