Mower runs better with choke on

[NateDN10]

Since it's actually started raining again where I live I hadn't had a chance to mow the lawn before last night, and the grass was really thick.

I discovered that my Honda Harmony 215 seems to run better (faster anyway) with choke on. I was able to mulch some sections of my lawn that I would've had to bag if it was just running on normal full throttle. Is this normal, or is it a sign that something is misadjusted?

It doesn't run poorly at normal full throttle compared to choke, just slower.

 

[Hokiefyd]

It sounds like it may be running lean; not enough fuel is getting to the engine to run properly with full air flow through the carburetor. The choke literally chokes air flow, and the mixture is correct at that lower air flow.

I would disassemble and clean the carburetor and/or check for other sources of fuel restriction.

 

[fordman65]

Yes something is not adjusted right. Like the previous poster said it is definitely a carb adjustment. After adjusting your carb, try running some premium 92 or 93 octane through your engine. I know it sounds crazy, but I just bought a brand new John Deere lawn mower last year. I only run plus or premium gas in it. Never had a problem with it starting or running.

 

[95busa]

Carb fueling circuit may be clogged up....restricting airflow with choke makes the airflow and fuel flow equal

 

[Trav]

Put a little Berrymans chemtool in the tank. Not much about an ounce or so, let it idle for a few minutes to get it into the internals then let it sit a day or two.

Its a lot easier than taking stuff apart and is a good first step.

 

[The motor guy]

Originally Posted By: Trav
Put a little Berrymans chemtool in the tank. Not much about an ounce or so, let it idle for a few minutes to get it into the internals then let it sit a day or two.

Its a lot easier than taking stuff apart and is a good first step.


You can do that? So that stuff is powerful enough to eat away and any gunk in the jets?

 

[The motor guy]

to test if the carb is bad. Run it out full throttle and then apply full choke. If the engine doesn't stall out then the carb jet is clogged. You have to do this at full operating temperature for it to work.

 

[2004tdigls]

my lawn mower did the same thing, it ended up being a cracked intake manifold, apparently the new gas additives are eating the plastic

it stalled constantly but ran fine with the carb choked

 

[123Saab]

I had this issue once with my 310-8 Wheelhorse and replaced the fuel lines, took the cup off the carb and gave it a quick cleaning.

Also rinsed out the fuel tank.

Added a few caps of seafoam to fresh fuel and after about 5 minutes of uneven running it was running great.

 

[NateDN10]

Thanks for the suggestions!

 

[TFB1]

Originally Posted By: Trav
Put a little Berrymans chemtool in the tank. Not much about an ounce or so, let it idle for a few minutes to get it into the internals then let it sit a day or two.

Its a lot easier than taking stuff apart and is a good first step.


Bingo!!! And fixes the problem nine times out of ten...

 

[wag123]

Originally Posted By: Trav
Put a little Berrymans chemtool in the tank. Not much about an ounce or so, let it idle for a few minutes to get it into the internals then let it sit a day or two.

Its a lot easier than taking stuff apart and is a good first step.
The main jet has a restriction in it. Putting something in the gas tank will RARELY solve this kind of problem. The float bowl needs to come off and a small stiff wire poked through the main jet to clean it out. On some small engines the main jet is actually in the float bowl nut itself, just poke a stiff wire through the small hole in the side or top of the nut (the small hole is your main jet).

 

[JimPghPA]

I do not have a similar mower, however many 4 cycle carbs have a very small passageway for air flow during idle. When that small opening gets clogged usually the engine will run much better at throttle positions above idle with the choke somewhat on.

Look for a very small hole (usually located on the floor of the air passageway just behind the choke plate), but it also may be located on the front of the carb near the gasket that goes between the carb and the air cleaner. If that is the case there will be a passageway in the gasket.

Often that little idle air breather passageway requires cleaning by removing the idle adjust screw, and then blasting the passageway with some spray carb cleaner. Passing a thin wire through that passageway along with some carb cleaner may also clear it out.

If clearing that idle air passageway solves the problem, you could use a fuel additive such as RedLine SL-1 to keep it clear. And it probably would not hurt to spray some WD-40 down that passageway when you put it away for storage.

I have also seen carbs that have a bad gasket around the bowl require use of choke to run properly, so if the cleaning of the small hole for the idle air does not do the trick, you might want to replace the bowl gasket if it looks like it might not be sealing properly.

Again these suggestions are generic, and not for any particular carb, I do not have a mower like the one you talk about, but have seen these suggestion work on small 4 cycle engine carbs.

 

[JimPghPA]

BTW the smaller the size of an air passageway is the easier it is for it to get clogged, which is probably why the small idle air passageway being clogged is such a common problem.

 

[yonyon]

Originally Posted By: motor_oil_madman
Originally Posted By: Trav
Put a little Berrymans chemtool in the tank. Not much about an ounce or so, let it idle for a few minutes to get it into the internals then let it sit a day or two.

Its a lot easier than taking stuff apart and is a good first step.


You can do that? So that stuff is powerful enough to eat away and any gunk in the jets?


Usually Trav gives pretty good advice, but this crazy idea of using carburetor cleaner to clean a carburetor is just too crazy and off the wall...

 

[HerrStig]

When my Honda mower acted up at the start of a season I put a bit of RedLine cleaner in the tank, ran it, and let it sit. Next time i needed to mow it ran fine.

 

[wag123]

Trust me Nate, you have a restricted main jet. In the 25 years I have been working on small engines I have seen this exact same problem at least 10000 times and 99% of the time the main jet is restricted. The other 1% of the time the carburetor has been loose or the intake manifold gasket has been bad causing a massive air/vacuum leak.
If the air bleed is plugged the engine will run RICHER and closing the choke will flood the engine and kill it. If the bowl gasket is bad the carb will leak.
You COULD put something in the gas and it MIGHT dissolve a varnish buildup in the main jet, but if there is a bit of dirt restricting it, the additive won't help. Cleaning the main jet manually will cost you absolutely nothing unless you take it to someone like me who will charge you for doing it. BTW, the stiff wire that I use is the steel wire inside plastic twist ties. Just strip off an inch or two of the plastic and you have a FREE main jet cleaning tool.

 

[wag123]

I take it back, there is ONE other thing that will cause the described symptoms. Old gas. When gas gets old it looses volatility and the engine requires a lot more of it to run, which means that you will need to keep the choke closed to supply the extra fuel that it needs. Eventually the gas will loose so much volatility that it won't burn at all, then the engine won't start, even with the choke.

 

[NateDN10]

I think it makes sense that the jet is partially blocked. This mower used to be my dad's, and was his dad's before that, but was rarely used by either of them. The first time I started it up, I got halfway through the lawn just fine, and then it started intermittently losing power, almost like the gas tank was nearly empty. When I was almost finished with the lawn, it went back to normal.

So probably this is caused by a partial blockage, and that was caused by a more complete blockage that eventually worked itself out.

 

[artificialist]

Originally Posted By: wag123
I take it back, there is ONE other thing that will cause the described symptoms. Old gas. When gas gets old it looses volatility and the engine requires a lot more of it to run, which means that you will need to keep the choke closed to supply the extra fuel that it needs. Eventually the gas will loose so much volatility that it won't burn at all, then the engine won't start, even with the choke.

That, and if he has to use E10 gas, the problem is even worse.