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I was given a Husqvarna RZ4619 zero turn mower from a friend who said it hadn't been used in 2 years and had been kept outdoors. The mower has a Briggs and Stratton 19hp intek, single cylinder engine on it.

I have done the following;

Oil/oil filter change
changed spark plug
replaced fuel lines, filter, and pump
replaced carburetor

The engine runs great while sitting idle (both at lowest speed and highest speed). However, As soon as the engine is placed under a load, either by engaging the blades or by driving forward at full speed, the engine sputters then evens out, then sputters and evens out about every 10 seconds or so.

One side note, the new carburetor that I put on does not have the air adjustment screw like the old one had. Could that cause this issue? If not, any other suggestions on what to check?

Thanks!

HelpNeed3d said:

the new carburetor that I put on does not have the air adjustment screw like the old one had.

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What do you think this is telling you? Wrong carb right?

Was this an OEM Briggs carb? Doesn't sound like it. Going to have to boil clean out the Briggs carb. Check for vacuum leaks.

Here's another one to add to your bag of tricks. Dump and flush out the fuel tank.

Valve adjustment time couldn't hurt.

Is it over-heating causing poor power output? Are the cooling fins clean? Take pictures of the block and cooling fins. Post them up here.

slomo said:

What do you think this is telling you? Wrong carb right?

Was this an OEM Briggs carb? Doesn't sound like it. Going to have to boil clean out the Briggs carb. Check for vacuum leaks.

Here's another one to add to your bag of tricks. Dump and flush out the fuel tank.

Valve adjustment time couldn't hurt.

Is it over-heating causing poor power output? Are the cooling fins clean? Take pictures of the block and cooling fins. Post them up here.

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The new carburetor is after market. I tried finding information before i bought it on whether you can replace a carb with the air mix screw with a carb that doesn't have it. I couldn't find anything. Other than the air mix screw, the carb is identical. So are you saying the carburetor is likely the issue? I will try cleaning the old one and putting it back on to see if that makes a difference.

Wouldn't a vacuum leak cause it to surge even at idling?

Fuel tank was flushed, cleaned and new fuel added when I replaced the fuel lines.

I have not messed with the valves.

I'm sure the fins are not squeeky clean, the mower has been sitting outside, uncovered, for 2 years. I did check them for wasp nests, critters etc. but haven't given them a good cleaning. I don't have a photo right now. I can post one later when I get home.

HelpNeed3d said:

Wouldn't a vacuum leak cause it to surge even at idling?

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Depends on how bad the leak might be.

I HOPE it hasn't sit for 2 years with Ethanol fuel in the carb. That stuff is like acid eating away corroding the aluminum.

HelpNeed3d said:

Fuel tank was flushed, cleaned and new fuel added when I replaced the fuel lines.

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Good man.

HelpNeed3d said:

I have not messed with the valves.

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Might be worth a look. You are loosing power. Either air/fuel related or some valves might be out of spec.

HelpNeed3d said:

I'm sure the fins are not squeeky clean, the mower has been sitting outside, uncovered, for 2 years. I did check them for wasp nests, critters etc. but haven't given them a good cleaning. I don't have a photo right now. I can post one later when I get home.

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I'm holding you to this LOL.

Yes, it definitely sat with fuel in it. That’s why I went ahead and just replaced everything from tank output to the carburetor.

I’m trying to take pictures, but it keeps telling me the files are too large. I’ll keep trying. But the fins are not bad, obviously a little corroded but not super dirty.

So it was doing the exact same thing before you started replacing things??????

HelpNeed3d said:

Yes, it definitely sat with fuel in it. That’s why I went ahead and just replaced everything from tank output to the carburetor.

I’m trying to take pictures, but it keeps telling me the files are too large. I’ll keep trying. But the fins are not bad, obviously a little corroded but not super dirty.

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Turn the cam resolution down in the phone or resize in Windoze.

HelpNeed3d said:

Yes, it definitely sat with fuel in it. That’s why I went ahead and just replaced everything from tank output to the carburetor.

mom trying to take pictures, but it keeps telling me the files are too large. I’ll keep trying. But the fins are not bad, obviously a little corroded but not super dirty.

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Forest#2 said:

So it was doing the exact same thing before you started replacing things??????

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No, it had been sitting for 2 years with gas in it before I got it. It wouldn’t start at all, so I just went ahead and replaced all those things to get it going.

slomo said:

Turn the cam resolution down in the phone or resize in Windoze.

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What is the Mb limit for files?

HelpNeed3d said:

What is the Mb limit for files?

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I think I got it. Hopefully these attach. Wanted to post a video also of what the engine is doing, but it was WAY to big.

I would remove the ignition coil. Polish all the mounting areas/pads and screws. Remove all that rust. Reinstall the coil. Might not be a fix but darn sure couldn't hurt.

Man she is pretty clean. Someone has been washing her down recently. For a mower that was stored outside and sit for 2 years, she is a clean one. Never had a used mower that clean under the hood.

HelpNeed3d said:

What is the Mb limit for files?

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Not large like 1-2mb maybe? It will tell you when you try to upload one. It will complain really and not tell the size limit.

Does it bark back when you turn the key? Does it sound like it has compression?

Most likely you have a carb issue. Your air to fuel ratio is off. It wants more fuel. Clean the Briggs carb and reinstall.

Cooling fins look okay.

I would look at the valves for sure.

slomo said:

Does it bark back when you turn the key? Does it sound like it has compression?

Most likely you have a carb issue. Your air to fuel ratio is off. It wants more fuel. Clean the Briggs carb and reinstall.

Cooling fins look okay.

I would look at the valves for sure.

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I’m not sure what you mean by barking back, sorry. It cranks when I turn the key and runs great. The issue only starts when I engage the blades or accelerate going forward.

I’ll try cleaning, reinstalling the old carb, but I’ll have to get a rebuild kit for it first. The old gaskets and Irving’s were toast.

I’ll see if I can find someone to help me with the valves, that’s something I’ve never tackled before.

thanks for all of the input!

Does it sound like the piston is compressing some air and fuel in the cylinder? Like a starter sound, ruv ruv ruv..... Insert your best engine cranking noise here LOL.

engage the choke slightly
If the problem goes away that says too lean a mix on the MAIN jet and this very well could be because the cheap knock off has a smaller main jet.
These carbs are not like car carbs when anything over idle pulls in the main jet.
On a mower it runs on the idle jet even at "high idle" of 3600 rpm, that is why it is called HIGH idle .
The main jet does not come into play till the governor allows the throttle plate to open up under load .
IT could also be an air leak via the head gasket .

bertsmobile1 said:

engage the choke slightly
If the problem goes away that says too lean a mix on the MAIN jet and this very well could be because the cheap knock off has a smaller main jet.
These carbs are not like car carbs when anything over idle pulls in the main jet.
On a mower it runs on the idle jet even at "high idle" of 3600 rpm, that is why it is called HIGH idle .
The main jet does not come into play till the governor allows the throttle plate to open up under load .
IT could also be an air leak via the head gasket .

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Thanks I’ll check that also

slomo said:

Does it sound like the piston is compressing some air and fuel in the cylinder? Like a starter sound, ruv ruv ruv..... Insert your best engine cranking noise here LOL.

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Yes, it does.

When it is running, does it even out if you partially close the choke?

To easily do photos on your computer, put the photo on your screen, then go to the pop up menu search, and type in "snipping tool" or "snip", and take a snip of your pic, and use that to upload here.

I'll take $850 on "what are the symptoms of installing a cheap carb" please.

sgkent said:

I'll take $850 on "what are the symptoms of installing a cheap carb" please.

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Thanks for all of the information and suggestions. You all helped me confirm what I already suspected. The after market carburetor was the issue.

I soaked the old carb and cleaned the jets, used the gasket, Oring etc. from the new carb and put the old carb back on the mower. Everything is running like a champ now!

thanks again for all the help!

awesome

We see this day in and day out
I see it almost daily in the workshop
But every time we warn people that the bulk of the cheap carbs are junk some one always chimes in with "I have bought X and all mine were perfect "
As you have found out it is very much an unluckydip
Glad to hear you have it running now go mow .

slomo said:

Does it bark back when you turn the key? Does it sound like it has compression?

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To be more specific, there's two types of sound you'll hear: 1) a rythmic thump thump thump, or 2) a linear hum, like the starter is turning with no resistance. Which one does yours sound like?

In any case, my money is on the carb. No reason to believe it is faulty at this point.

Edit: crap, I missed his post of triumph. Glad it worked out for ya.

slomo said:

What do you think this is telling you? Wrong carb right?

Was this an OEM Briggs carb? Doesn't sound like it. Going to have to boil clean out the Briggs carb. Check for vacuum leaks.

Here's another one to add to your bag of tricks. Dump and flush out the fuel tank.

Valve adjustment time couldn't hurt.

Is it over-heating causing poor power output? Are the cooling fins clean? Take pictures of the block and cooling fins. Post them up here.

Click to expand...

Blowing out the Fuel line is also one less thing to suspect. You may have to drill out the jet. Check Governor spring if there is/was one.

slomo said:

What do you think this is telling you? Wrong carb right?

Was this an OEM Briggs carb? Doesn't sound like it. Going to have to boil clean out the Briggs carb. Check for vacuum leaks.

Here's another one to add to your bag of tricks. Dump and flush out the fuel tank.

Valve adjustment time couldn't hurt.

Is it over-heating causing poor power output? Are the cooling fins clean? Take pictures of the block and cooling fins. Post them up here.

Click to expand...

So if the carb looks exactly like the old one, look where the air mixture screw is on the old compared to the new. I did the same for a snow blower and the new card had the air mixture hole plugged. I removed the plug and screwed in the air mixture screw into the new carb and it ran perfect.

Sounds like it could be in the governor. If it is pulsing low under load, then going back high the governor is opening the throttle it could be adjust wrong, your carb is not supplying enough fuel to maintain rpm, valves misadjusted, or you compression is low.

Clean the flywheel and mag\coil with emery paper and size gap to 0.010" (business card). Load from deck could be pulleys\spindle bearings. Check main drive belt routing and idlers.

I've had 2 engines that I've worked on that did that no matter if it was OEM carburetor or Aftermarket. The problem that I finally found on them was the valve adjustment was so far out of adjustment that I'm surprised it ran. Adjusted the valves and the lost power was back and it ran great.

HelpNeed3d said:

I think I got it. Hopefully these attach. Wanted to post a video also of what the engine is doing, but it was WAY to big.

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In the pictures I see rusty coil and flywheel. The first thing I would do is take some sand paper and clean the coil metal surface where it is near the flywheel and then clean the flywheel of rust. Re-gap the coil to flywheel. I have found that rust decreases the magnetic flux from the flywheel and can effect the spark and that can reduce power which is what seems to be happening with the pulsing.

Curtisun said:

In the pictures I see rusty coil and flywheel. The first thing I would do is take some sand paper and clean the coil metal surface where it is near the flywheel and then clean the flywheel of rust. Re-gap the coil to flywheel. I have found that rust decreases the magnetic flux from the flywheel and can effect the spark and that can reduce power which is what seems to be happening with the pulsing.

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Would you please explain what scientific principles apply to this post
How exactly dose derusting the surface affect the magnetism or the magnetic flux in the coil ?
There is probably a Nobel prize in physics awaiting you if you can do it.

This is a place where genuine advice is given to those who seek it
Not a place where Face Book foolery is perpetuated .
The only place that needs to be clean is the grounding point for the laminations which is where it touched the crankcase plus the area under the mounting bolt heads if they are plated and not black.

Furthermore mechanically attacking a magnet with a wire brush actually damages the magnet
If you understood how a magnet is made & works then that would be obvious
Unless there is rust thick enough to bridge the gap between the laminations & the magnet, the rust is not a problem.
If rust was a problem then the parts would have a rust proof coating of some sort .
Now it you want to clean some thing then clean the spaces between the alternator magnets as magnetic dust collects there which shorts out the magnetic fields and reduces the output from the alternator .

Replace entire length of fuel line. It has possibly delaminated and
collapsing due to ethanol fuel, especially since it's been sitting for two years.

Those Briggs Single Cylinder Intek
Engines have a crappy bolt design on the cylinder head . The spacing of the bolts is quite a distance on the piston bore to the oil return ports . And this allows the gasket to blow out quite easy . I usually do 5 or 6 of these engines for head gaskets in a season.
On these engines after about 10 hrs use the head bolts will need.retorqed again . The heat stretches the bolts and the gasket compresses and loosens. If you've done 4 gaskets I would try this method. If it blows again I would suspect a warped head face or cylinder face. As for the pulsing I would do a valve adjustment and try it. Still there.. possibly a leaking intake gasket or o ring or intake tube. If those appears to be sealed then your aftermarket carb isn't jet fat enough to run your engine and is starving for gas.

HelpNeed3d said:

I think I got it. Hopefully these attach. Wanted to post a video also of what the engine is doing, but it was WAY to big.

Click to expand...

I could guarantee your coil surfaces are totally rusted. Cleaning the coil surfaces and the magnet on the flywheel will increase your spark and allow for a cleaner burn in the cylinder. When i do a tune-up i always clean the coil and magnet . This eliminates poor spark.

smallenginerepairs said:

I could guarantee your coil surfaces are totally rusted. Cleaning the coil surfaces and the magnet on the flywheel will increase your spark and allow for a cleaner burn in the cylinder. When i do a tune-up i always clean the coil and magnet . This eliminates poor spark.

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Where do you guys get this BS from
Magnetic flux is totally unaffected by rust , paint or any other coating .
In fact agressive wire brushing can destroy the surface magnetism
Pinch your kids / grandkids science text book and read the physics section like you should have done at hight school
And please stop spreading this total BS

The only thing that needs to be clean is where the coil mounts to the block to create a ground connection.