Posted by Bob M on March 30, 2009 at 10:16:28 from (151.190.254.108):
In Reply to: 300 Carb help posted by ed in cny on March 30, 2009 at 09:20:03:
Ed – A light coat of black inside the venturi is pretty much normal. It comes from an occasional light backfire in the manifold (not unusual when starting a cold engine). Also some gasolines will leave a light residue inside the venturi as the gas evaporates. Don’t be too concerned about it.
Regarding fuel consumption, if the exhaust is clear (no trace of black) and the tractor has good power and runs smoothly, there's not a lot you can do to improve fuel consumption.
However here's some possible causes of high fuel consumption: - Ignition timing (should be TDC at idle) - Ignition advance (should advance to around 30 deg TDC by 1,200 RPM). - Dirty or plugged air cleaner - Dragging brake(s) - Hydraulic system malfunction. If the hyd reservoir gets hot after running a few minutes there’s a problem here. - Engine running too cold (missing or broken thermostat) - Operating in too low a gear. (If load permits, better fuel economy can be had by “gearing up and throttling down”) - If you are using fuel with a lot of ethanol in, fuel economy will be less (ethanol has less energy that straight gasoline) - Excessive idling. These engines can burn a lot of gas “just doing nothing”
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Carb adjustment:
The upper screw with its head facing the front of the tractor is the idle mixture The upper screw coming in from the side of the tractor is the idle speed adjustment. The bottom, angled screw is the power mixture.
Initial mixture settings are 1 turn open for the idle and 3 turns for the power.
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To set the carb first get the engine fully warmed up and make sure the choke is fully open. Then: 1 – With the engine idling turn the idle mix screw in/out as required until you get the best (smoothest, fastest) idle. 2 – Reset the idle RPM if required with the idle speed screw. 3 – Now open the governor all the way. Turn the power screw out until the engine just starts to run rough. Now turn it back in slowly until the engine again runs smoothly. 4 – Close the throttle and repeat #1 and #2 if necessary. 5 – With the engine idling snap the governor open as fast as possible. If the engine stumbles as it picks up, open the power screw and additional 1/8 – ¼ turn or so.
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