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Good Morning!

I have been struggling to get my mower to start properly without injecting either carb cleaner into the carb or gas directly into the chamber. What have I done to fix this issue?

1. Cleaned the Carb (3x now) - this included removing everything from the bowl and tube, physically cleaning all the jet holes and using both carb cleaner and compressed air
2. Replaced the intake manifold (small crack that eventually became a big one after removing carb)
3. Cleaned chamber according manufacture instructions
4. Checked cold compression (reads 100psi both without and with oil)
5. Charged battery
6. Checked teeth of flywheel
7. Replaced magneto (Original was extremely rusty and the spark was a little weak)
8. Checked spark plug gap (0.30) and resistance (resistance was within tolerance, 6,000 ohms I believe if my memory serves me right)
9. Checked spark - sparking like a mad man
10. Cleaned alternator ring of rust
11. Replaced fuel line with new fuel line
12. Dried out fuel tank and replaced with new non-ethanol fuel
13. Drained all oil and replaced with new oil

I should note that I was able to get the engine to start on the second turn after cleaning the carb for the third time. It started right up but since then it won't start. This makes me think it is the carb but after so many times cleaning it, I am just not sure that is the issue. The carb was replaced two years ago with a Briggs and Stratton Walbro. When I cleaned the carb the first time there was some gunk in the carb but none of that showed up after the first cleaning.

Any suggestions?

When you cleaned the carb, did you do these two things? One, remove the main nozzle and make sure all the jets were open? Two, replace the float needle and seat, plus set the float level? Without doing #1 and possibly #2 you will be fighting a loosing cause.

did you check your float level?
I believe this is the correct carburetor......

I removed the float, main nozzle, all of it. I cleaned them all out. The float moves freely and gas fills the carb but doesn't flood.

Just because it seals properly doesn’t mean that it is at the proper height. If you didn’t set the float level properly, it may be set too low causing a lean starting and running condition.

Have you checked to make sure the choke is closing completely. Just a little gap of not complete closing can causing starting issues.

Rivets said:

Just because it seals properly doesn’t mean that it is at the proper height. If you didn’t set the float level properly, it may be set too low causing a lean starting and running condition.

Click to expand...

My float doesn't look like it has any adjustment. The float is plastic, even where the needle sits in the float. Not sure how I would adjust it...

ILENGINE said:

Have you checked to make sure the choke is closing completely. Just a little gap of not complete closing can causing starting issues.

Click to expand...

It appears to be closing all the way. I have also tried starting at different levels of choke to no avail.

Did some more research. These plastic floats cannot be adjusted. What can happen is the needle gets worn and doesn't stop fuel from flowing into the bowl, thus causing flooding.

I took the carb apart a fourth time and cleaned it a fourth time. I attached pictures to show the bowl, main jet, fuel jet, etc.

I tried to crank it, no change. It just turns over and over without even giving a hint of starting. I sprayed a tad bit of carb cleaner into the air filter intake and it roared to life just fine. Fuel is making it into the carb bowl - that is not an issue. As you can see from these pictures, when I took it apart, a lot of fuel came out. I also tried without the air filter on, with the air filter on, gas cap on, gas cap off, etc. No change.

For some reason, the mixture is not rich enough to cause combustion to occur.

The rngine starts using the IDLE circuit
The IDLE circuit has it's own jet and passage down the side of the carb
On some it is fixed and covered by welch plug
If that passage is not clear the engine will not start full stop
This is why most of the techs here ignore it when a poster says they have cleaned a carb
99% have not actually done it properly

If you assemble the float with the needle and seat in place, the float should be level. If the float is higher on the side opposite the float pin you will have a lean starting and running condition. More than likely the seat has swollen, causing the needle to shut of the fuel to soon. If you find this is the case you can try to resolve the problem by replacing the needle and seat, making sure the seat is installed properly. Other solution is to replace the carb. There are tricks to adjusting a plastic float, but I don’t post them as an amateur can easily ruin the float if not done correctly.

And THIS is the method of cleaning out the idle circuits for cabs that are sealed
Back in post # 3 scrubby posted a link to the photo instruction for cleaning Walbro carb which actually has that link in it but a lot fail to see it
IF your carb has removable idle jets and not having a solenoid usually means it was supplied with removable jets, these ned to be cleaned and adjusted in order to start easily .
Unfortunately you did not put a side view photo of the carb so I can not identify which one you have.
Also note in the instructions it shows where the pick up for the idle circuit is in the main jet tube
If you have a can of any goo, carb cleaner / WD 40 etc with a long straw poke it into the pick up hole then looking into the engine end spray down the hole
You should see the fluid coming out of the tiny holes on the left ( right when viewing from engine end ) side of the carb throat shown in step # 24 under the yellow dots in the above mentioned cleaning instructions .
You should also see goop coming out of them when sprayed down the pilot air path shown in step # 13 outlined in yellow
Everyone usually checks the pilot air passage because it is there easy to see but most forget about the pilot fuel passage cause you can't see it easily

The other method to check it is working is to fill the float bowl and blow low pressure air down the yellow hole only and check for fuel ( or what ever you put in the bowl ) coming out of those holes and by low pressure we are talking 5-10 psi of via one of those cans of compressed air for dusting cameras and electronics .

Mine is a Walbro LMT with a permanent idle jet, where the idle adjustment screw is. I did try by best to clean that out by spraying carb cleaner into the idle adjustment screw hole where that idle just passage is. I will do it again and check them as you mentioned to see if they are blocked. If they are blocked, I will probably replaced the ball as mentioned. I have the tap set already when I was working on a generator.

Double check that the Flywheel Key is not partially sheared on Crankshaft.

micahmesser said:

Good Morning!

I have been struggling to get my mower to start properly without injecting either carb cleaner into the carb or gas directly into the chamber. What have I done to fix this issue?

1. Cleaned the Carb (3x now) - this included removing everything from the bowl and tube, physically cleaning all the jet holes and using both carb cleaner and compressed air
2. Replaced the intake manifold (small crack that eventually became a big one after removing carb)
3. Cleaned chamber according manufacture instructions
4. Checked cold compression (reads 100psi both without and with oil)
5. Charged battery
6. Checked teeth of flywheel
7. Replaced magneto (Original was extremely rusty and the spark was a little weak)
8. Checked spark plug gap (0.30) and resistance (resistance was within tolerance, 6,000 ohms I believe if my memory serves me right)
9. Checked spark - sparking like a mad man
10. Cleaned alternator ring of rust
11. Replaced fuel line with new fuel line
12. Dried out fuel tank and replaced with new non-ethanol fuel
13. Drained all oil and replaced with new oil

I should note that I was able to get the engine to start on the second turn after cleaning the carb for the third time. It started right up but since then it won't start. This makes me think it is the carb but after so many times cleaning it, I am just not sure that is the issue. The carb was replaced two years ago with a Briggs and Stratton Walbro. When I cleaned the carb the first time there was some gunk in the carb but none of that showed up after the first cleaning.

Any suggestions?

Click to expand...

With carb installed on mower and ready to start the carb butterfly is by default open. Wide open. If not, good luck get'n it started.Linkage issues or adjustment can cause this.

riceski@gmail.com said:

REPLACE CARB

Click to expand...

It is a brand new carb from a year ago.

Gord Baker said:

Double check that the Flywheel Key is not partially sheared on Crankshaft.

Click to expand...

This is something I have thought about but would that cause it to only start with a squirt of carb cleaner or gas in the chamber? Seems like it would also run poorly when started but it runs great.

Replace the carb. They are not that much money and all indications are for whatever reason, their is something defective internally with your current carb.

With the carb properly installed the throttle butterfly should be wide open, but the choke butterfly should be fully closed when starting.

wtjackso said:

Replace the carb. They are not that much money and all indications are for whatever reason, their is something defective internally with your current carb.

Click to expand...

It is $140 for the OEM carb. The Chinese ones I have tried before fail within a month or two, those are the cheap ones. The one that is on the mower now is an OEM one I bought a year ago. Worked great until last week when I went to mow.

micahmesser said:

Good Morning!

I have been struggling to get my mower to start properly without injecting either carb cleaner into the carb or gas directly into the chamber. What have I done to fix this issue?

1. Cleaned the Carb (3x now) - this included removing everything from the bowl and tube, physically cleaning all the jet holes and using both carb cleaner and compressed air
2. Replaced the intake manifold (small crack that eventually became a big one after removing carb)
3. Cleaned chamber according manufacture instructions
4. Checked cold compression (reads 100psi both without and with oil)
5. Charged battery
6. Checked teeth of flywheel
7. Replaced magneto (Original was extremely rusty and the spark was a little weak)
8. Checked spark plug gap (0.30) and resistance (resistance was within tolerance, 6,000 ohms I believe if my memory serves me right)
9. Checked spark - sparking like a mad man
10. Cleaned alternator ring of rust
11. Replaced fuel line with new fuel line
12. Dried out fuel tank and replaced with new non-ethanol fuel
13. Drained all oil and replaced with new oil

I should note that I was able to get the engine to start on the second turn after cleaning the carb for the third time. It started right up but since then it won't start. This makes me think it is the carb but after so many times cleaning it, I am just not sure that is the issue. The carb was replaced two years ago with a Briggs and Stratton Walbro. When I cleaned the carb the first time there was some gunk in the carb but none of that showed up after the first cleaning.

Any suggestions?

Click to expand...

Sounds like the choke isn't completely closed, manually try to

SOLVED!!!!!

To everyone, thank you!

I found the problem. As some people indicated, it was the choke. In one of my removals, probably the first one, the linkage had slipped out causing it to basically "float". I feel like an idiot not checking this!


Half of the choke was hanging outside of the channel. Once I put it back in, it started right up no problem.

Amen Bert.

Engines start off the pilot or low speed jet. These use tiny pilot jets and clog easily. Same as the emulsion tube you showed in your pictures.

What you've shown looks clean. Need to clean what you haven't yet.

Hope you kept the original magneto. All you had to do was de-rust the mounting areas where the 2 screws go. This improves the ground to engine block allowing current/voltage flow. Course the coil could be shot too.

slomo said:

Amen Bert.

Engines start off the pilot or low speed jet. These use tiny pilot jets and clog easily. Same as the emulsion tube you showed in your pictures.

What you've shown looks clean. Need to clean what you haven't yet.

Hope you kept the original magneto. All you had to do was de-rust the mounting areas where the 2 screws go. This improves the ground to engine block allowing current/voltage flow. Course the coil could be shot too.

Click to expand...

I have the original, I will keep it just in case I need a backup.

However, after four good cleanings it was the linkage that was the issue. Turns out the choke linkage had come partially out of the slot it is supposed to slide in, causing the choke to not engage.

micahmesser said:

SOLVED!!!!!

To everyone, thank you!

I found the problem. As some people indicated, it was the choke. In one of my removals, probably the first one, the linkage had slipped out causing it to basically "float". I feel like an idiot not checking this!


Half of the choke was hanging outside of the channel. Once I put it back in, it started right up no problem.

Click to expand...

I had the exact same thing happen not long ago. Took me forever to figure out. Finally got it running and it threw a rod.

Richard Milhous said:

I had the exact same thing happen not long ago. Took me forever to figure out. Finally got it running and it threw a rod.

Click to expand...

Oh no! That is awful.

micahmesser said:

SOLVED!!!!!

To everyone, thank you!

I found the problem. As some people indicated, it was the choke. In one of my removals, probably the first one, the linkage had slipped out causing it to basically "float". I feel like an idiot not checking this!


Half of the choke was hanging outside of the channel. Once I put it back in, it started right up no problem.

Click to expand...

Excellent. As aggravating as it is one gets a lot of satisfaction in figuring things out on their own. As my dad used to tell me experience is the best teacher.

bertsmobile1 said:

The rngine starts using the IDLE circuit
The IDLE circuit has it's own jet and passage down the side of the carb
On some it is fixed and covered by welch plug
If that passage is not clear the engine will not start full stop
This is why most of the techs here ignore it when a poster says they have cleaned a carb
99% have not actually done it properly

Click to expand...

Assuming the throttle butterfly is mostly closed when trying to start it, then yes the idle circuit will be used but when the throttle plate is completely open under any operating circumstances then the main jet will be used because there is no airflow restriction being created by the throttle plate to form manifold vacuum and pull fuel through the idle ports. Since there is no airflow restriction, air will be passing through the venturi at a high speed, creating the vacuum which relative to the atmospheric pressure of the float bowl will push up fuel through the main jet into the emulsion tube and intake. At partially closed throttle plate positions both jets can work together, even at full throttle no load.