[quote author=6E574A4C5D5B7B6871380 link=1559102549/15#15 date=1559341446]
justin_o_guy2 wrote on 05/31/19 at 11:36:00:True but please note I wrote "Properly-jetted". Utility engines such as those found in lawnmowers do not have to meet the same EPA standards as motorcycles nor do they have to compete for MPG numbers.
When I got my brand new 2019 Honda CRF230F it would not run unless it had been warmed up for about 10 minutes. If I shut it off and it sat for more than a few minutes it needed partial choke again. Now with proper jetting it only needs choke and warmup for a few minutes.
In the old days we had systems such as EFE (Early Fuel Evaporation) and CCS (Controlled Combustion System) to help carbs and engines during warmup periods. If an engine comes off choke very fast and does not exhibit a lean condition during warmup it is jetted too rich.
I think there is some "room" for "opinion" about what "proper" jetting. An air/fuel ration of 14.7:1 is good for economy - the ratio for maximum power is around 12.5:1. An engine that is jetted within this range will run pretty smooth - and this spread is why a primitive carb can be made to run well........there is some wiggle room
Some of the new engines are running far leaner than that to help reduce emissions and satisfy the EPA......and if these engines have carbs and chokes - they are engines that are really finicky and require long warmup. In my opinion these engines are legal in the eyes of the EPA - BUT - they are not jetted "properly. I agree with VorteCPI and any engine that needs to sit in the driveway and idle for 5-10 minutes before you can add throttle and ride away is not jetted properly and it needs some larger jets!
There are "lean burn" engines that run fuel/air ratios as high as 65:1 - those do require fuel injection and computers to make them run properly....it would be impossible to get them to run with a carb.
https://en.wikipedia.org/wiki/Lean-burn