McCULLOCH FG2000Tc engine starts but idle

The idle adjustment screw will probably have a spring on that screw and will push directly on the throttle linkage. You just adjust this screw until the engine idles like you want it to. I believe on saws, they have to idle to where the clutch will not engauge when the engine is at idle. As for the mixture screws the low speed screw (L) you adjust when the engine is at idle, the high speed screw (H) you adjust while the engine is running with a good bit of throttle. Once you get the idle speed where you like it, then all you have to worry about is the mixture screws. When adjusting the screws, just listen to the engine, to much one way and the engine will run rough and sputter, to much the other way the engine will run rough and maybe start hunting (reving up and down). One thing to check on these small 2-strokes is that the air filter and the muffler are not clogged cause if they are, then you would be having to adjust the carburetor to make up for the air restrictions that these two problems can cause which would mean that the carburetor isn't actually adjusted perfectly.

Possible Idle air control, simple to change on the throttle body

Make sure the air cleaner is clean. Turn both jet needles CW to stops (lightly), then back each out CCW 1-1/2 turns. The engine should start and run--allow to warm up, then pull the throttle full on. Turn the H needle CW until the engine starts to speed up, but still 4-stroking. Final adjustment is when the engine 4-strokes no load, but immediately 2-strokes when cutting. Release the throttle and adjust L needle CW until the engine idles fairly well, but will allow the engine to follow the throttle. Adjust the idle speed screw so that the chain doesn't turn and the engine continues to run. Hope this helps!

Turn both jet needles CW to stops (lightly), then back out each CCW 1-1/2 turns. This is a basic setting that should allow the engine to start and run. Start the engine and allow to warm up, then pull throttle full on. Adjust H needle CW until the engine starts to speed up, but continues to 4-stroke. Proper setting is when the engine 4-strokes unloaded, but immediately 2-strokes when cutting. Release the throttle and adjust L needle CW for better idle, yet allows the engine to 'follow the throttle'. Adjust idle speed screw so that the chain stops turning, but the engine continues to run. Hope this helps!

If the two needles are at the CW stops (lightly), then turn each out 1-1/2 turns CCW. This is a basic setting and the engine should start and run. Check the fuel filter, air filter and muffler for plugging. Allow to warm up, then pull the throttle full on. Adjust H needle CW until the engine begins to run faster, but still 4-stroking. Proper final adjustment is when the engine 4-strokes running free, but immediately 2-strokes when cutting. Release the throttle and adjust L needle CW till the engine idles fairly well, yet will allow the engine to 'follow the throttle'. Set the idle speed screw so that the chain stops turning, but the engine continues to idle. Hope this helps!

a pit\ston might not be working properly

HAVE THE COOLANT TEMP SENSOR CHECKED TO SEE IF IT IS FUNCTIONING PROPERLY.HOPE THIS HELPS. BEST OF LUCK. LET ME KNOW?

pump the primer till it's full of fuel Before you start it