Posted by Steve@Advance on February 14, 2019 at 05:52:37 from (24.182.105.179):
In Reply to: Carb help on Super C posted by Midway on February 13, 2019 at 20:58:37:
Sounds like the main jet is clogged with dried ethanol deposits.
The carburetor is simple and field serviceable.
Take some pictures before removing the carb, note the position of the linkages, etc.
Take it off, dump the fuel. Clear off the work table, lay out some cardboard if you desire. There will be 2 adjustment screws, an idle screw and a main jet screw. Gently turn each screw in until it just bottoms, don't force it. Count and note the number of turns each takes to bottom. Carefully remove the bowl screws, ease the bowl off, being careful not to tear the gasket. Pull the pin holding the float, remove the float and needle valve.
Have some spray carb cleaner ready, clean out the inside of the bowl, spray through each passage. You can go online and look up that carb under "Zenith fuel circuits" or whatever carb it has. There will be illustrations of where each fuel passage goes. By spraying cleaner in each fuel circuit, and watching it come through it's destination, you can verify that circuit is open. Sometimes the deposits are hard, sticky residue that doesn't respond well to the cleaner. In that case a small stiff wire can be used to scrape the residue out. Just don't enlarge any jets, force the wire, or break the wire off inside a passage. If you have compressed air, blow everything clean and dry. Check the float, give it the "shake test", feel for any fuel inside, there should not be any.
Once everything is cleaned up, carefully reassemble everything. With the float installed it should sit level with the upper housing inverted. There will be a stain line where the fuel level normally sits. It should be parallel with the gasket surface. Carefully reassemble the bowl to the body. Reinstall the adjustment screws, turned in to bottom, then backed out to where they were as noted.
Reinstall the carb, make sure the linkages are correct. Before connecting the fuel line, I like to open the tank valve and let some fuel flush out the line. The incoming fuel must be clean! Any trash gets into the needle/seat will hold the needle valve open and you will have flooding, very frustrating, best avoided!
Once back together, it should start. Be ready on the kill switch just in case of a runaway. Not likely, but it happens.
Once the engine is warmed up, and idling around 500 RPM or less, adjust the idle mixture. That's the smaller screw up close to the mount flange. Turning the screw out leans the mix, in richens it. Turn the screw out until the idle get rough, in until it runs smooth, then in about another 1/8 turn.
The main adjustment is a little more involved. With the engine at idle, suddenly open the throttle and observe the response. The engine should take the quick throttle without hesitation. Start turning the main screw in 1/4 turn at a time until the engine hesitates on quick throttle, then back it out 1/4 turn at a time, repeating the test until it will take sudden throttle without hesitation. A single puff of black smoke is the goal.
Of course, engine performance is not solely based on the carburetor. If there are other problems, weak ignition, timing, low compression, valve lash/valve problems, everything works together. If it still doesn't run or runs poorly, check the other components before condemning the carb. It will only work as well as everything else allows it to.
Hope this helps, don;t be afraid of it, don't hesitate to ask questions.
If you plan on keeping this tractor, a shop manual will be a very valuable investment. It will pay for itself in mistakes not made!
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