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New paint looks god but doesn't make the unit run. Send me your OEM M/S Carb and I will rebuild it to OEM specs, guaranteed to run. What's there to 'figure out' with your Cheena carb? Units are all the same basic parts. New stuff not manufactured like OEM stuff and certainly not pre-set to specs. Don't think you can slap it in out of the box and it will run fine. Model year unimportant - ALL N's use the same carb - TSX-241. Adjusting the carb on the tractor requires teh engine to be up to operating temperature first. Making idle and needle adjustments requires short, 1/8 turns at time then WAIT til engine catches up. Once internal unit is cleaned and float, venturii (did you set it upside down?), and choke & throttle plates set right, make initial OEM settings. Don't mess with governor -carb mist be right first. New carb or old carb, if you don't pass the fuel flow test first, the problem isn't with the carb - you have plugged screens on Sediment Bulb, a plugged gas tank vent, or a plugged filter in the carb elbow inlet. Remove NPT drain plug and open Valve ---should get 1 pint of fuel in 2 minutes, unobstructed flow. Also try line at inlet elbow too. See if this helps: MARVEL-SCHEBLER TSX CARBURETORS FORD TRACTORS HOW TO ADJUST When adjusting the carb, turn main jet out 1-1/2 turns and leave it. Then adjust side pointing idle mixture screw to fastest idle, not smoothest. This procedure has to be done when the engine is really warmed up and often takes 2 or 3 tries. When you turn a screw in or out, watch how may turns you go, best to only go 1 turn at a time, then WAIT for the engine RPMS to catch up. The proper method is to make adjustments while under load and at certain rpms, but early 8Ns have no Proofmeter to show R's so best guess scenario takes over. Both Ford and Marvel/Schebler say to set both the side-pointing idlemix {Idle Mixture Adjustment Needle} and the down-
pointing main jet {Main Power Mixture adjustment Needle} to 1-turn as a starting point. I set the down-pointing main jet {Main Power Mixture adjustment Needle} to 1-
1/2 turns and don't fool with it anymore. Then adjust the side-pointing idlemix {Idle Air Mixture Adjustment Needle} for fastest idle; not the smoothest idle. Next, adjust the behind the carb idle-speed (throttle) set-screw for very slow 400-rpms idle. Do that idle mix {Idle Air Mixture Adjustment Needle} adjust for maximum idle at least 3-times. Do it like this: 1. Adjust idle mix jet {Idle Mixture Adjustment Needle} until RPM increases 2. Adjust idle-mix set screw {throttle idle-speed set-screw} until the engine nearly stops (as slow as you can get it unless you have a tach that tells you 400 rpm) 3. Grasp the rod between the carb & governor & twist/shake it slightly; the slop in these rods often stops the adjustment cam from moving. Repeat steps 1 - 3 three times with about 10-15 minutes between tries. Remember the side-pointing idle mix {Idle Mixture Adjustment Needle} is out for lean, in for rich. I don't let my N's run dry. The M/S carb has a cast iron bowl & it will rust when it gets dry. Running aluminum carbs dry is ok. The Main Power Adjust needle is CW for reducing fuel (leaner) and if fully functional will shut off all carb fuel (even idle) when screwed in fully CW to it's seat. This leans it to point that engine dies. You say that this results in backfire. Is that correct? Just before all the way in (so lean it just barely runs, I don't see that you should observe a rich-condition-black-smoke at this point. Do you see that at this point? The Idle Mixture Adjust needle is just the opposite, that is CCW leans the idle mixture. That is because the Idle Mixture Adjust needle controls AIR, unlike the Main Power, which controls fuel. More AIR (same fuel)=leaner idle mixture. CCW=more air=leaner. Main Power needle is generally not very sensitive except near fully closed (full CW), whereas the Idle Mixture needle is more sensitive.
Tim Daley(MI)
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