George is spot on, my 149 had the same issues, opened up the jetting a bit and it purrs like kitten.

I'm with this idea. If an engine used to run good now it's lean as you described then what changed? It's always dirt in the system somewhere. You can adjust to compensate for the lean condition but I would rather rather fix it than just put a band aid on it

When something like a sudden lean condition happens, I sometimes make a decision as to whether I should do carb cleaning or tweak the fuel/air mixture. And the compromised decision is to pop off the fuel bowl only and clean it out as well shoot carb cleaner where I can at the carb. I might find something, I might not. Quick and easy to do....if the fix is negative, then I take it further.

To all who said it's lean condition I have a few questions:

~If it's lean, then why does he have to push the choke IN as he accelerates it?
~If it's a plugged main jet, then why won't it idle? Doesn't take much fuel to idle, and he already stated it will run at full..... if it can get enough fuel to run at full, it should be able to get enough to idle.
~Why is the plug black?



To the OP:
~Once it warms up, how does it act under load? (Does it ever pull down hard, and you have to choke it to keep it running?)
~Do you still have to leave the choke on?
~After it's warm, will it start easily? (Without the choke)

You stated you bought it last summer. What all have you done to this machine/engine before now? Has it always ran like this since you've had it running?

I bought a cub that had almost the exact same symptoms, the guy rebuilt the carb and it never ran right again. After a bunch of messing around it turned out that the high speed needle was over tightened when it was reassembled and it bent, might not be your problem but it wouldn't hurt to pull the needle and check.

A little history on this machine could be helpful, has it always run this way, did it set a long time before you got it, what brand of carburetor is on this engine, is the throttle shaft sloppy in it's bore, is the carb to engine gasket in good condition?

Right or wrong, if it were mine, the first thing I would do is remove the high speed needle and make sure the little holes are all clean. The needle is hollow and it needs to be clean inside too. Sometimes crud inside the needle will give false impressions. Then put it back in and set it according to the manual (2 turns out, I believe).

If the tractor sat a long time I would think that a carb rebuild would be in order (disassemble, soak over night, blow all the passages out and install a new kit) Squirting carb cleaner down the throat does absolutely nothing.

I believe I would also check the timing.

After it warms up it runs absolutely perfect. I pushed a pile of wet snow half a block and it never stumbled at all. It takes a little less messing around when its hot but still doesn't start like it should. When I bought this last summer it was already doing this. It sat in a shed for years before I got it. All I've done to it is replace the spark plug and emptied the gas tank so I could fill with fresh gas. The tank had lots of crap in it so I removed it and washed it out really good. That leads me to believe some of that junk made it to the carb.

Yosemite Sam-
It started like this when I got it. It did sit for years. I have the Kohler carb, throttle shaft seems fine. After sitting so long I want to clean up the carb anyway, so I ordered a carb kit and will try to check timing while I wait for that to get here.

I took it as the op had to have some choke to accelerate at all
Maybe I miss read it.
I figured an expert would come along soon, and they did

Looked at the points today, had some buildup on them and there was barely any gap even after cleaning. I set it to recommended clearance. But I think I have bigger issues. After removing carb to get ready to rebuild I could see carbon buildup on the underside of the intake valve. I removed the head and its ugly. Lots of carbon on the valves and there is a thick buildup that hangs out past the cylinder wall that appears to have worn the top of the piston in that spot. Time to make some decisions about the future of this rig...