My LA105 is rough and sputters black smoke!

[Rob H. KCMO]

I noticed my jdla105 was making a slightly more popping noise out of the exhaust than normal. Barely noticeable. I finished my front yard and moved around to the back and at one instance it started running really rough, sputtering a bit of black smoke, and popping very loudly from the exhaust. I noticed the fuel was admittedly low, so I added fresh gas. No change. It idles fine, but any attempt to increase the throttle, popping, black smoke and rough.
Any advice would be greatly appreciated. Oh yeah, 415.3 hours.

 

[bczoom]

Welcome to the forum.
Have you performed any recent maintenance on it (e.g. an oil change)?
Most common causes can be:
Stuck choke
Clogged air filter
Problem in the carburetor

 

[Rob H. KCMO]

Total tune-up every spring. Oil and filter, fuel filter, air filter, fresh gas, etc.....

 

[bczoom]

Check your oil level. If it's too high, you can experience this problem.
You may have something clogged in your carb. Do you have a good fuel additive? E.g. SeaFoam or Mechanic in a bottle? I'd add that, run it for a few minutes then let it sit for a day then run it again to see if it dissolved the crud.

 

[Rob H. KCMO]

Thank you for responding Sir!
I very much appreciate it! I went to our local repair shop at 48th and Brighton he suggested mechanic in a bottle.
I replaced the fuel pump, fuel filter added the Mechanic In A Bottle. Thinking it may be some fuel related.
But the oil level was maybe a little low.
Much to my disappointment, after changing all that, it still ran pretty much the same.

 

[bczoom]

If your oil is high, it can be a problem. A "little" low isn't an issue.
Mechanic in a bottle needs to sit in the carb and fuel system for about a day to get full effect. Try again later today.

Did you check the choke to make sure it's not stuck? If you have an automatic choke, there's a thermostat that could have gone bad.

Is there any evidence of the head gasket leaking?

 

[Rob H. KCMO]

Thanks bc,
I honestly don't know where to look for the choke.
I'm leaning very much towards something fuel related. And a new carburetor off of Amazon is only 25 bucks. Just in case I'm going to change all the fuel lines today.
I really wish I could upload the video on here.

 

[bczoom]

I honestly don't know where to look for the choke.

It's on the the carburetor, first thing in the carb after the air filter. It's a flapper/plate that opens and closes to adjust fuel/air mix. When the engine needs more fuel (e.g. cold start), that flapper closes which restricts air flow and therefore more fuel in the mix.
If the flapper doesn't fully open as it should (see pic below of full open), you're getting too much fuel which can cause the issues you're experiencing. Pull the air filter and see if that flapper is fully open (as pictured below).

Being a newer tractor, it may have an automatic choke (as opposed to a choke lever on the dash). If this is the case, go to youtube and look for "automatic choke briggs and stratton" (Assuming you're tractor has that brand engine.

 

[Rob H. KCMO]

I want to thank everyone in this forum for your advice! I believe I may have found the problem. But in the process I got a sparkling clean fuel tank, all new fuel lines run, a brand new carburetor and a better understanding of how this lawn mower was assembled!
So, I was prompted to check the valve gaps. That could be an issue. I removed the valve cover and do a visual inspection first and notice that the intake rocker was EXTREMELY loose!
Having the adjustment specs I begin to Gap the Rocker and valves. But the intake adjustment nut I had to turn several more times than I did the exhaust. I adjusted the gap/lash on Both valves.
Thinking I was done as I start to clean the residual oil off the bottom of the case I noticed this circular piece of metal that was cupped. Immediately, I thought to myself, Rob you dipshit!
I took it out cleaned it off and knew exactly what it was. And that's why the intake valve rocker needed to be tightened down more than the exhaust valve rocker! (Pictures to follow.)
So this would explain the missing, extremely rough running and backfiring through the carburetor.
Now I'm going to go put this thing back together and see what happens.
Once again thank you gentlemen of this forum for all your advice!
Rob........

 

[bczoom]

Glad to hear you found it!
I wasn't going to go into the engine until we were sure the fuel system wasn't the culprit.
Did you get an OEM or aftermarket carb? If the latter, HANG ON TO THE ORIGINAL!
Aftermarket carbs are a hit or miss on whether they work and hold up over time.
When you get bored, rebuild the original and keep it handy with a new set of gaskets in case you need to go back to it.

 

[Rob H. KCMO]

Thank you BC!
I had every intention of hanging on to the original one. The new one, that I got from Amazon for $25, is identical. I had a hell of a time getting it started though. There are two connector wires on the bottom of the carburetor that I forgot to plug in. I plugged those in, and it fired right up! (when I do things like that I say, "I pulled a dipshit")

 

[bczoom]

There are two connector wires on the bottom of the carburetor that I forgot to plug in. I plugged those in, and it fired right up! (when I do things like that I say, "I pulled a dipshit")

From what I understand, at least one (and maybe both) of those wires are are for sensors or something you may not want to deal with down the line.

Pretty sure the first wire is some solenoid coming off the (red?) wire at the very bottom of your carb. That's the one that may have not let you start your engine.

CONFIRM but that's something to consider disconnecting. Go to youtube or someplace and look up the carb on that engine and you'll get all the details..