300 Utility fuel issue

[sunsettractor]

I've had this tractor for a few month's and have been trying to work the bugs out, it has quite a few. It has run very rich since it came to me, carb adjustments have helped , but only a little bit. Recently it flooded bad, gas was running out of the carb and it quit running altogether. Also, oil got contaminated with fuel, oil level on dipstick was an inch and a half over full mark. Removed carb and took apart, float was all beat up and full of gas. I soaked the carb for a couple days in parts dip, then again in CLR to bring the casting to like new appearance, purchased a rebuild kit and float from YT,the kit did not contain a new air mixture screw, just a load mixture screw, that screw was much shorter than the one that was in the carb and also too large to even fit through the carb, so I re used the old load screw. I used the clear hose in the carb bowl drain method to get the fuel level set to 9/16 below the bottom of the top carb casting, it stays at that level so I think the needle valve is sealing properly. With the load screw turned out four turns, and the air mixture screw out 1 or 2 turns, it starts right up, but the exhaust is thick black and the engine lopes at idle, upon opening the throttle, thick black smoke billows from the exhaust pipe and smells like raw gas. I lowered the fuel level in the carb bowl and made no difference, turning the air mixture to any position in or out makes no difference, with the load screw turned all the way in against the seat, it idles well and runs fairly smooth bot still puts out a black cloud of smoke when the throttle is opened up, but misses and runs erratic at full or close to full throttle. It is this way with the air cleaner hooked up or disconnected, so a plugged air cleaner is not the problem. Can anyone provide any suggestions as to what could be wrong here?? Other than go buy a different rebuilt carb I am kind of stuck....Thanks,Tom

 

[Andy Martin]

It's running worse now than before you cleaned it? Sounds like it is. Since the idle adjustment screw seems to have no affect on how it runs, that may be the source of the fuel bypass. The rotary valve in the throttle shaft is supposed to shut off air to the bleed circuit. I wonder if maybe it is not working, allowing fuel to be sucked in through the idles circuit all the time. Does the gasket have all the right holes in it?

 

[sunsettractor]

Yes Andy, the holes are lined up properly, I saw that if the gasket was upside down it would interfere, but that is not the case.

 

[D Slater]

Could be wrong but suspect the kit you got didn't have a idle mixture screw or a load screw if you have a gasoline 300 carburetor. Think the load screw you call to short is the idle air screw for a Super series back or other fuel besides gasoline in some later models.
Unless you have a internal fuel leak or a needle and float system defective the screws shouldn't mater if using the originals. If you have the correct load screw it should screw in enough to shut fuel to the carburetor off or limit fuel to a lean condition. Unless someone drilled the jet or the packing is to thick.
If you have a gasoline carburetor it has no off idle passage to slot the other poster referred to.
Knowing the carburetor and kit number may be a help.

 

[sunsettractor]

The carb # is 361525R92, I purchased kit # IH103 from Yesterdays Tractors, it did not have the idle screw or correct load screw so I used the ones that were in the carb, they appeared to be in good shape, The load screw threads into the jet nice, but as I mentioned, the tractor will only run well with the load screw turned all the way in against the seat, which would "normally" kill the engine, at least on the other tractors I have. I have read that 5 turns out is a standard setting for the load screw on this engine, when the carb was apart you could see that with the screw out 5 turns, there is a substantial gap between the needle and the jet seat. I have let the tractor sit for a while with the gas petcock open and a clear hose attached to a fitting on the bowl drain to monitor the fuel level, have also drained the bowl and let it refill several times to check the operation of the float and needle and seat, it seems to work as it should, Something is not right, just having a hard time locating the problem, Thanks for the replies...tom

 

[sunsettractor]

Actually it does run better now than it did before, but only with the load screw turned all the way in against the seat. Backing the load screw away from the seat results in alot of black smoke.

 

[D Slater]

Don't think it's the problem but what I was trying to say is if that carburetor kit had a adjustment screw in it, screw is for idle mixture adjustment on different carburetors than yours. If sure the needle and seat is not leaking or no internal leaks or cracks in the bowl into fuel passage, check for the seat the load screw goes to being drilled out. If you have a micrometer find something around .047 diameter and then bigger to try. Off the top of head I think those should be .048 but can look if needed. 1/16 drill size seems to be the favorite size used for someone without the small numbered drills. Another thing even if you checked fuel level sitting make sure the float doesn't have enough play to rub the bowl in use. Also if nothing found in fuel system make sure ignition system including spark plugs are working correct. Sometimes when not the plugs will never clean up enough to burn fuel and run right.