carb troubles on 135 gas

Only being able to run with full choke is indicative of a weak spark, or too lean a mixture. Check the spark by removung the wire from the center of the distributor cap and holding it about 3/16" from a good ground while trying a start. You should have a FAT, BLUISH-WHITE SPARK. Not yellowish, orangey, or a stringy bluish, but a FAT, BLUISH-WHITE SPARK. If you have a poor spark, look for corroded, burned, or poorly set points, bad or corroded connections in the primary ignition circuit (the one that runs between the battery to the distributor through the key switch and the coil).Key switchs can cause high resistance in the circuit so jump the keyswitch with a jumper and see if it makes any difference. Make sure that the coil polarity is correct( the wire from the distributor to the coil should be connected to the coil terminal with the same sign as the battery ground).Then check your timing and make sure that your centrifugal advance is working.

If the ignition system checks out, then proceed to the fuel system. makse sure that you have full flow to the carb by removing the plug from the bottom of the carb hold a container to catch that expensive gas and open the tank valve. You shouls have a STEADY, CONTINOUS GUSH OF FUEL FOR AS A GOOD 30-45 SECONDS. If the flow is intermitent, or stops, you might have a clogged fuel vent, a clogged carb float valve, or some of the screens in the line are clogged. Check the "secret filter" in the fuel inlet elbow of the carb as well as the those in the sediment bowl. Open the gas cap and repeat the test to see if the vent is clogged. If they are clear and the flow is poor, the flaot sytem s either plugged or maladjusted or thier is sufficient sediment in the fule bowl to prevent the float from dropping. Rap the carb with a wooden block to dislodge a "hung" float. if you still can"t get adequate fuel flow, you have to pull the carb and check to see if the float valve has some dirt in it.

If fuel supply checks out, then adjust the power jet, usually a big screw on the top of the fuel bowl. Usually 1-1/8 to 1-1/2 turns out from full in is good range for the M-S carbs on the older tractors. Don"t know about yours. The idle mixture on the old M-S Carbs is about 3/4 turn out. Again, I don"t know about yours.
If adjusting the mixture doesn"t help and it"s still needs full choke to run, I would suspect that you have a air leak around the carb"s metering section. That"s usually the throttle sgaft seals, the connect flange gasket between the carb and the intake manifold, the intake manifold gasket, or the intake manifold is cracked. this allow air to get into the cylinders, bypassing the carb venturi and hence the mixture is lean.

Do these checks, one at a time, in the order I have specified and you"ll efind the problem. Write the results down so you can analyze them and also keep the results in case you have future troubles.

Hope this helps.

I believe the float should be set level, which should position the end of the float 1/4 inch above the sealing surface when turned upside down.

My bet would be that you have debris in the carb passages. Isolate the tank, drop the plug from the bottom of the carb, turn gas on, to check for flow to the carb. Get a can of carb and choke cleaner, dissassemble the carb, remove the adjustment screws, and spray into each passage in order checking each clear before proceeding to the next. On reassembly, ensure that idle screw on the throttle plate is set to where the plate is just slightly open (1/64).

There is likely a better way to adjust a carb, but here is my recommendation. Set the idle mixture screw (little) out about 1-1/2 inch. Tighten main mixture screw (big one). Start engine, and tighten screw til idle starts dropping off, back off til idle starts dropping off, center screw halfway btween these two points, or at the point that the engine runs fastest. Now move to the main mixture adjustment screw and back it out 1-1 1/2 turns. If the engine wants to die reset throttle plate minimum setting. Adjust this screw til the tractor does not stumble when engine is revved. Now put her to work adjusting main til the engine takes fuel well, does not stumble on the governor, and has clean exhaust. During this phase, if the engine starts popping or loses power immediately, it is lean. If the exhaust turns black, power drops off or hesitates on the governor, it is rich. Err toward rich. Lean condition can damage an engine if left.

Lean is mean, but fat is happy.

Good Luck,

Aaron