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350U running lean

F

Formerly PaMike

Member
I have been posting on here about the tractor not running right and a lot of you have given me info. The tractor wouldnt run well after coming back from paint and having a 12 volt conversion. I found an intake manifold leak. Fixed that and it ran better. Found a bushing out in the governor. Fixed that and it ran even better. Still is fussy when you start it. Gotta mess with the choke in and out till there is some heat in the engine. Once there is heat in the engine it idles well and runs well but on sudden load it will sometimes stumble. I pulled out the needle on the main jet and sprayed carb cleaner back though. That seamed to help some. I set the needle back to 5 turns out. I pulled the idle needle. When running your finger down the taper of the needle I could feel a ridge where the angle changed. Is this correct? Pulled 2 spark plugs. Electrode is very light brown. I would say too lean. I would have thought if the carb needed rebuilt it would be running rich. Does a 12 volt conversion cause an engine to run lean since there is better spark for the combusion??
 
I would say you need to take the Carb apart and clean it!

Don't Forget the Screen on the inlet of the carb it may have dirt in it or the dirt in the settlement Boal!

Cliff S
 
No, the clean burn of good spark is not a factor. The main jet and/or Power circuit is still somewhat plugged up. I'm glad it is running. Jim
 
Electrode should be gray or even almost white with the correct mixture, but brown is better than black. With 5 turns out you are not likely to get a clean plug unless you run full load for a few hours. As stated in the other post, clean the carb and put a kit in it. Spray on carb cleaners won't do much. Then experiment and set the main jet at about 3.5 turns out. If it pulls what you want it to, it is ok.
 
I have found over the years that my 300U's are very cold blooded and want to be warm before they will run smooth.
On my snowplower I used to play with the choke till it warmed up but then a few years ago I came up with a routine that works.
On a cold start, I pull full choke, as soon as it kicks I push the choke in about 3/4 of an inch and leave it there till it warms up. Works every time and I have had the same plugs in it for at least 5 years.
Dell
 
I think it would be running rich with the main jet opened 5 turns and the plugs would probably be blacken and getting some smoke from the exhaust.

You're probably not getting enough gas to the carburetor causing the engine to run lean. You need to disconnect line at the carb to see if there's a full stream of gas from the tank. If that looks ok pull the tube fitting in the carb and look for a plug screen. If that is clean your main jet is probably plugged and a carb cleaning and rebuild is in order. Hal
 
I had checked the stream of gas early on and it looked good. 5 turns out is what the manual says...might as well go for a carb rebuild and see what that does.
 
The thing thats wierd is ours was never cold blooded. If it fired it ran and didnt stall. Might run rough at first but never stalled....
 
Out is richer on the main jet, leaner on the idle jet. Five turns out on the main, and you will need a fuel truck to follow you around.
 
5 turns out with full load, the manual also says less for ligher loads, you can tailor to fuel to what you are doing at the time.
 
hey PA, just for the heck of it you should make sure that there are no additional vacuum leaks around the intake, if you found one there might be more causing a lean A/F mix, and that would make adusting your carb seem impossible. grab you a can of carb cleaner at the auto parts store and gently spray it around the carb base and the intake and see if your idle picks up, you can pin point a very small vac leak this way. also you can spray a little carb cleaner right into the intake/carb throat and see if it runs better by artificially inriching like this will also tell you your not getting the right amount of fuel and you have some sort of fuel restriction...and or vacuum leak..
 
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