a properly running 4 stroke will never have a problem at idle or trolling with a little load, the oxygen sensors are constantly adjusting the fuel mixture by A. changing injector pulse and B. adjusting the IAC (idle air control) valve on the throttle body or bodies. they are running lean at idle and just off idle to save fuel, at mid throttle they are keeping it as close to stoichometric (14.7 air fuel ratio, which is the most complete burn) and under heavy load and sudden acceleration they are keeping the engine on the rich side for engine safety. on variable cam engines they are adjusting valve overlap. and while all of this is going on, your engine knock sensors are adjusting ignition advance and retard based on the rich/lean misfire threshhold of maximum performance. if you wanna see how fast this is all taking place, hook up an air fuel gauge to your upstream oxygen sensor, it looks like simon says on acid (red yellow green autometer style) for the motorheads out there, we know this isnt as accurate as a wideband o2 but it will certainly get the point accross.
old 2 strokes? basically look at your weed whacker and add ignition timing with ignition coilpacks. they are not as good on gas, and premixing will use a considerable more amount of oil because the vro pumps and all the like would pull the mixture back, i believe in excess of 70:1. they will gum up bad over time if not treated. my engines sat all last year so i cleaned the carbs before running, they all looked like they had sinus infections...absolutely gross.
another note...guys with the older rudes and johnsons, carb rebuild kits are rarely necessary....make sure u have brown gaskets on the sides of the carbs(updated gaskets for harsher fuel content)take them apart and inspect. 90 percent of the time you can get away with cleaning. problem number 2 for rough running thats a fuel problem should always be the check valves that reside on the side of the manifold....
hope this helps?
steve
old 2 strokes? basically look at your weed whacker and add ignition timing with ignition coilpacks. they are not as good on gas, and premixing will use a considerable more amount of oil because the vro pumps and all the like would pull the mixture back, i believe in excess of 70:1. they will gum up bad over time if not treated. my engines sat all last year so i cleaned the carbs before running, they all looked like they had sinus infections...absolutely gross.
another note...guys with the older rudes and johnsons, carb rebuild kits are rarely necessary....make sure u have brown gaskets on the sides of the carbs(updated gaskets for harsher fuel content)take them apart and inspect. 90 percent of the time you can get away with cleaning. problem number 2 for rough running thats a fuel problem should always be the check valves that reside on the side of the manifold....
hope this helps?
steve