Rough Idle - Dirty Carb or Something Worse?

[l008com]

Here is video of the machine in question. Funny thing is, on video it doesn't really sound like it's doing anything. But in person, its definitely running rough. You can see at the end of the video, how the handle is vibrating.

Ok so the backstory. This is a trash rescue. It was overfilled with oil and wouldn't run. I drained the oil and gas, replaced with the proper amount of oil and fresh gas. It was hard to get it initially started at that point. I had to use a few squirts of starter fluid. But after a minute, it started running under its own fuel and has ran good since. It starts up with one pull every time, even when cold. But it runs very rough after that first pull for 5 to 10 seconds before it starts running better. Better is relative because it still runs a little rough. It feels like maybe its misfiring but it could just as easily be fuel related.

It has a new spark plug and air filter.

So the question is, is this just an issue of a dirty carb, or might there be something worse going on. Like bad compression or bad ignition coil or something like that?
Once I got the machine starting easy and running well, I put 1 oz of seafoam in the tank, then topped it off with fresh gas. I then mowed my whole kinda large lawn with it. I was hoping that would clean out the carb but it doesn't seem to have had any effect. Possibly it just needs to run longer. Also possible its too dirty for that and needs a "real" carb cleaning. Also possible the problem is something else entirely.

What do you think?

As I'm typing this, the video is playing on loop and its so annoying that the audio recording in the video kind of hides the roughness of the idle. One thing you can gleam from the video is that the roughness isn't THAT bad. Its has never stalled on me or anything. Once its running, it stays running. Its just a little rough, it doesn't run like the honda engine on my husqvarna mower.

 

[kbowley]

Sounds like the automatic choke may be sticking closed or the carb is dirty. To check for the choke issue, pull the air filter off and start it, then look in the carb throat to ensure the choke is open. You will need either another person to hold the handle down or tie it to the handlebar so it stays depressed. Let us know. If the choke is opening like it should, pull the carburetor and clean it well.

 

[platefire]

Did you check the air filter. With the overfill of oil it may have saturated the filter.

 

[l008com]

Update:
Yesterday I fired it up, clamped the handle, and pulled the air filter off. No change.
Also regarding the choke, first dumb question, is the choke the FIRST butterfly you see looking into the air intake from the air filter?
If so, then it was opening up fully. It was moving slowly, I don't know if that's normal or not. So maybe its slow and that may be causing the kind of "clunky" start. But once its running for a bit, it opens up fully and I still get that not perfect riding, kind of feeling like misfiring.

Is there anything ELSE that might be causing this, before I dig in to the carb? I would think possibly the spark plug, but the plug looked almost mint. Like the previous owner replaced it after over-filling the oil, trying to fix the "now it won't start" problem.
I just want to make sure its the carb so I don't replace it and still have the same problem.

If everything still points to the carb, I'm tempted to mow my lawn with it one more time, with seafoam in the tank again, before I start taking parts off. Because I love it when the lazyman's fix works.

 

[Bertrrr]

The choke plate is the one you can see on top, I've never had much luck cleaning a carb unless I take it down and do it manually , the smallest particle of rust or whatnot can be stuck in the jet , take it apart and blow through everything with compressed air and then some WD 40 and reinstall. Also make sure your tank is clean

 

[l008com]

Yeah so the choke opened slowly but it definitely did open fully.

I have had a few engines over the years that ran rough, and with some seafoam treatment over the long term, they would clear up and run well again. But the plan is to get this thing running good and sell it. I don't have time to mow with it all summer. So I'll probably just do the carb. I also have very bad luck taking carbs apart. So if they're only $20 on ebay, I'll probably just replace it. I know many people don't like ebay carbs but I've had very good luck with them. Very few duds.

 

[kbowley]

Yeah so the choke opened slowly but it definitely did open fully.

I have had a few engines over the years that ran rough, and with some seafoam treatment over the long term, they would clear up and run well again. But the plan is to get this thing running good and sell it. I don't have time to mow with it all summer. So I'll probably just do the carb. I also have very bad luck taking carbs apart. So if they're only $20 on ebay, I'll probably just replace it. I know many people don't like ebay carbs but I've had very good luck with them. Very few duds.

Pretty please, do not purchase one of those aftermarket Chinese carbs off Amazon, it won't run right. Purchase the OEM carb and solve the problem correctly. They are not expensive. Get the model number off the machine and got to Partstree.com and get the part number for the carb. If you provide me with the model number (it may be under the bagger cover and it is either silver or white or on the rear of the chassis behind the engine). That looks like a Briggs engine?, so probably a plastic carburetor. Alternatively, take the carb to a small engine shop and have it cleaned. They are very simple carbs to clean as there is no low-speed circuit. Simply remove the two screws holding the bowl on, clray some carb cleaner through the brass main jet, remove the pin from the float and spray carb cleaner into the inlet seat, put it back together and pop it back on. Here is a YouTube video with instructions.

 

[l008com]

Ok I've now mowed my lawn twice with this mower, and its a pretty big yard for a small push machine like this. No change in sputtering/misfiring at all even with all the seafoam I ran through it. I even ran it dry then did a little more mowing with just clean, straight gas, incase I was overdoing it with the seafoam. Nada.

So I'll be replacing the carb and I bet it runs perfectly after that.

 

[Tiger Small Engine]

Ok I've now mowed my lawn twice with this mower, and its a pretty big yard for a small push machine like this. No change in sputtering/misfiring at all even with all the seafoam I ran through it. I even ran it dry then did a little more mowing with just clean, straight gas, incase I was overdoing it with the seafoam. Nada.

So I'll be replacing the carb and I bet it runs perfectly after that.

Seafoam makes people feel better, like they did something, the majority of the time. However, usually is not the solution or even marginally helpful. It is always better to keep OEM carburetor and clean first before buying an aftermarket carburetor. That said, I have had great results with most aftermarket carburetors I have purchased.

 

[l008com]

I have to disagree on the effectiveness of seafoam. It doesn't always solve the problems but it has helped a lot more engines for me than it has done nothing for. Two mows isn't a very long treatment but because I need to sell this mower and finish it's video, I really don't have time to mow with it all summer to see if it works, especially when new carbs are $10 shipped. But I've had very good luck with sea foam actually DOING stuff, and by stuff, I mean making engines that run a little rough, run like they should.