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I have a Cub Cadet 2166 I got from an auction for a steal. I am getting it in running order, and at this point it is running, cutting, and moving well. I do however have an odd motor issue.

The motor seems to have a 'miss' at any RPM. This miss is accompanied with a momentary loss of power. Whenever the motor requires more fuel (going up a hill, engaging the mower deck PTO) the miss/loss of power is more noticeable. Sometimes, this miss goes completely away after the motor warms up. Other times, like today, the miss stays when the motor is completely warm. This miss also seems to not have a set pattern, meaning it might go 5 second for one, then 10 for the next, then 7 for the next, etc. I have a video showing it clearly, but I need to find a site that will let me host the 35 second clip/MB size. EDIT: Uploaded it to my Youtube channel, if this is allowed. It is just a clip of the mower running:
At first I thought it was the carb, but the thing starts fine, and when the miss goes away, the motor throttles up and down with no issues. I then noticed today that the in-line fuel filter was basically empty. I have used various in-line filters, so I know they can work fine with some air in the bulb, but this was next to nothing in the filter. The fuel runs from under the frame, up next to the engine, and then to the top where it enters the fuel pump.

Anyone run into this before?

So I went ahead and disconnected the fuel line from the in line filter to the fuel pump. I poured some fresh gas into a small container and ran the motor on that. The motor ran the same with the same miss, so I'm thinking maybe fuel pump.

At the same time, when I disconnected the line and placed it in the container, some black material, probably line varnish, came out and settled on the bottom. I went ahead and ordered 10 feet of 30R14 carb line with a new fuel filter and B&S fuel pump. I'll replace everything between the fuel tank and the carb.

i think you're on the right track

That is an old mower so those fuel lines are probably well past their replacement dates
Take the carb off,pull it down and give it a good clean
Check that the fule solenoid is working properly and if it is then pull the kill wires off the coils and see it that ends the problem.
At that age you get chaffing of the kill wires that can give a similar sort of random surging
When I get one of these to diagnose , Ir remove the hood then fir a pair of red in line spark testers so I can see them when mowing and do a test mow after dark ( so I can see the red flashes )
When running full speed they should glow constant red
If they flash as the engine surges then I know it is a coil problem so then I disconnect the kill wires to see if it is the coils or the wiring.
A bit of a job but as you know it is a big job to get the blower housing off one of these to access the wires so the extra time diagnosing is well worth doing .
When I suspect the fuel supply I run an external fuel tank directly to the carb, directly to the fuel filter then directly to the fuel pump.
The mechanical fuel pumps are very reliable but they do wear out so when buggered I do an impulse pump conversion as was done on the latter models

Scrubcadet10 said:

i think you're on the right track

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bertsmobile1 said:

That is an old mower so those fuel lines are probably well past their replacement dates
Take the carb off,pull it down and give it a good clean
Check that the fule solenoid is working properly and if it is then pull the kill wires off the coils and see it that ends the problem.
At that age you get chaffing of the kill wires that can give a similar sort of random surging
When I get one of these to diagnose , Ir remove the hood then fir a pair of red in line spark testers so I can see them when mowing and do a test mow after dark ( so I can see the red flashes )
When running full speed they should glow constant red
If they flash as the engine surges then I know it is a coil problem so then I disconnect the kill wires to see if it is the coils or the wiring.
A bit of a job but as you know it is a big job to get the blower housing off one of these to access the wires so the extra time diagnosing is well worth doing .
When I suspect the fuel supply I run an external fuel tank directly to the carb, directly to the fuel filter then directly to the fuel pump.
The mechanical fuel pumps are very reliable but they do wear out so when buggered I do an impulse pump conversion as was done on the latter models

Click to expand...

Thanks for the info and tips!

The mower sat for a bit before the auction, based on some of the way the dirt and the tires looked. The lines being done in makes a lot of sense, it doesn't look like they were ever replaced.

For the carb cleaner, can I just use spray can carb/choke cleaner? I usually have CRC brand stuff on hand. I'll admit to not being good with carbs, but a simple remove and clean can't be that hard.

For the fuel solenoid, I am not sure my mower has one? I checked the Cub Cadets parts diagram and did not see one in the tank or in line. https://www.partstree.com/models/2166-13a-214g100-cub-cadet-garden-tractor All I have is the black and round fuel pump on the side of the engine. My Motor is the B&S Vanguard 18, which seems like it was not original. Everything I find points me at a Kohler motor.

I do have a spark plug in-line tester I will test with.

Yep, you can use spray can carb/choke cleaner.
The fuel solenoid will be on the Carburetor bowl, if it has one. The proper name is "anti afterfire valve". There is a rubber plunger on the solenoid that when the key is in the off position (you turn the mower off) it blocks the main jet passage to prevent that big B A N G, if raw fuel gets drawn into the engine and passed into the muffler/exhaust as the engine is winding down.

Scrubcadet10 said:

Yep, you can use spray can carb/choke cleaner.
The fuel solenoid will be on the Carburetor bowl, if it has one. The proper name is "anti afterfire valve". There is a rubber plunger on the solenoid that when the key is in the off position (you turn the mower off) it blocks the main jet passage to prevent that big B A N G, if raw fuel gets drawn into the engine and passed into the muffler/exhaust as the engine is winding down.

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Ahh ok, the mechanic I had this with when I brought it home from the Auction actually disabled this. At the time of the Auction the mower ran only on Starting fluid. He said as soon as he disabled this, the mower ran on it's own fuel. Could this being disconnected cause this surging maybe?

EDIT - Found a cleaning video, might try this when I replace the lines and Fuel pump.
Or I will just make a delete screw to go into the carb

When there is no power to the solenoid (unplugged) it is in the state of blocking fuel. If they fail and the customer doesn't want them replaced, i just cut or grind the plunger off flush with the top of the threads and screw it back in.
and i wrap the + wire up in electrical tape and fold it up out of the way on the mower.

The solenoids very rarely fail
The just get gummed up
You spray them with your CRC then work the plunger in and out till it all evaporates and repeat till the needle clicks back when pressed down
The carb will need an ultrasonic bath clean or a boil with a couple of dish washer tablets Plain powder does not work as good to remove the built up varnish , tar, gum
Outdoorpowerinfo.com has detailed photo instructions on pulling down your carb

Or just clean those the fuel solenoids in USC.

You might use something like SeaFoam in your fuel per instructions on container before getting into tearing things down, some people have had very good luck with it. Never used it myself, never needed to.

Walt Conner

Before tearing into the carb I would be checking the ignition system. I know everyone is focusing on a fuel problem, but a chaffed spark plug wire or kill wire would have the same symptoms. I’d be hooking my inline spark testers to both plugs and make sure that I wasn’t losing spark to one or both cylinders.

I would start with a clean fuel system. From the gas cap to the carb. Mower this old and OP found trash in the line. No doubt got passed onto the pilot and main jets ect.... Time for a "Bert-boil" carb cleaning.

On the ignition, I would remove the coils. Sand slash polish the mounting areas to refresh the coil mounting ground. Give the coils a proper shot at either working or not.

Have you ever removed the engine cover and cleaned the cooling fins and ALL around the block? Yearly maintenance item and super critical to these air cooled engines. Fins need to be like a new engine clean.

Well, I just replaced the entire fuel system. I verified the Gas tank is clean inside, that it is flowing fuel out fine. I replaced the lines all the way to the carb. New Fuel Pump, and new fuel filter. It is still doing the same thing. I went ahead and threw the in-line spark tester. The left side spark is constant, even when the power cuts out briefly. The right side is not as constant, and when the power cuts out, the in-line spark goes away briefly, then cuts in again and the motor comes back up.

I did not tear into the carb today, but I am not sure that is an issue here. I will probably attempt to get at the solenoid and do a carb clean tomorrow. I have a multi-meter, is there a way to check that the ignition coil is actually bad? I'd rather test it first then spend 50$ on a guess/misdiagnosed part.

EDIT - For some reason the comments after my last post did not refresh until I just posted this. Didn't mean for it to sound like I was ignoring anyone, I appreciate all the advice and help so far

slomo said:

I would start with a clean fuel system. From the gas cap to the carb. Mower this old and OP found trash in the line. No doubt got passed onto the pilot and main jets ect.... Time for a "Bert-boil" carb cleaning.

On the ignition, I would remove the coils. Sand slash polish the mounting areas to refresh the coil mounting ground. Give the coils a proper shot at either working or not.

Have you ever removed the engine cover and cleaned the cooling fins and ALL around the block? Yearly maintenance item and super critical to these air cooled engines. Fins need to be like a new engine clean.

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I just got this at an auction 2 weekends ago, I am slowing bringing this back to 100%. I do need to pull the engine shrouds and such off. The mechanic who I had originally dropped it off at to get working said I might need to lift the engine out of the frame to get at the coils. I also need gaskets for the valve covers, i see them seeping a little.

Testing with the inline tester indicates to me you have an ignition not fuel problem. Looks to me like your going to have to pull the engine on that unit to access the coils. Sometimes you might get lucky and just have to remove the hood. No way to test todays electronic coils without special equipment, but I’m guessing you will find bad wires as I posted before. If so you’ll just have to repair the wiring.

Rivets said:

Testing with the inline tester indicates to me you have an ignition not fuel problem. Looks to me like your going to have to pull the engine on that unit to access the coils. Sometimes you might get lucky and just have to remove the hood. No way to test todays electronic coils without special equipment, but I’m guessing you will find bad wires as I posted before. If so you’ll just have to repair the wiring.

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Winner Winner chicken dinner! Found half of a dried husk of a field mouse, and a bunch of chew marks on the coil bodies, and the wires going to and from the ignition coils. The worst one might have been making contact with the engine shroud:










Also, the bad coil side was where I found the field mouse body, and has a valve cover leak which packed the fins in good. I have to run to the store and get some more cleaning agents, but I already cleaned a lot of packed in greasy dirt on the back side of the cylinder:






So to be safe I am ordering 2 valve gaskets and 2 ignition coils to be done with it.

Does the surface on the flywheel/stator contacts need to be rust free? All the plates that look like they are for the stator/generator on this thing have surface rust. Wasn't sure if that mattered.

EDIT - Might be the spots for the ignition coils actually; they line up with the body of the coils as it rotates.

I see no reason to worry about a little rust on the flywheel or stator. If you have a pressure washer and air compressor or leaf blower, I would be using the to clean and dirt that unit. To bad you threw all that money into the fuel system.

Rivets said:

I see no reason to worry about a little rust on the flywheel or stator. If you have a pressure washer and air compressor or leaf blower, I would be using the to clean and dirt that unit. To bad you threw all that money into the fuel system.

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I don't mind. The hoses were starting to disintegrate on the inside. Just from moving them around, the fuel that came out had lots of black sediment. Plus, I don't have to worry about it for a long time now, as the lines I got are formulated specifically to resist ethanol and additive breakdown. If not now, I'd have had to deal with it in the near future probably

The hardest part now is waiting for the parts to come in and then remembering where all the shroud bolts go haha

Found the rest of the field mouse while I was pressure washing and using the compressor. Also got better shots of some of the chewed wires. Going out to look at the solenoid now, and then it is pretty much waiting until the parts get in.

Solenoid was snipped off. Pulled it out and there was just a nub, so no need to worry about that anymore

XTwarrior1985 said:

Does the surface on the flywheel/stator contacts need to be rust free? All the plates that look like they are for the stator/generator on this thing have surface rust. Wasn't sure if that mattered.

EDIT - Might be the spots for the ignition coils actually; they line up with the body of the coils as it rotates.

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No
Magnets are not affected by rust coating them
If it was a problem they would have some sort of surface protection applied at the factory
Same story for coils. I have seen laminations fanned out from severs rust & the coils work fine
As for your mower, change your winter lay up routine
At the last mow for the season change the oil then wash the mower, remove the blower housing and leave it that way all winter
Firstly mice will not find the open engine an attractive winter address and if they can not afford to move into a better neighbourhood then you will see them so can evict them easily .
Finally fins should be cleaned annually and wires check for fraying & chaffing so you kill 2 birds with the one stone

bertsmobile1 said:

No
Magnets are not affected by rust coating them
If it was a problem they would have some sort of surface protection applied at the factory
Same story for coils. I have seen laminations fanned out from severs rust & the coils work fine
As for your mower, change your winter lay up routine
At the last mow for the season change the oil then wash the mower, remove the blower housing and leave it that way all winter
Firstly mice will not find the open engine an attractive winter address and if they can not afford to move into a better neighbourhood then you will see them so can evict them easily .
Finally fins should be cleaned annually and wires check for fraying & chaffing so you kill 2 birds with the one stone

Click to expand...

Thanks for the info and advice. In this case, I bought the mower at an auction 2 weeks ago, so I am just getting around to checking this stuff now. Though, to be honest, if the coils hadn't been damaged I would have never pulled the shrouds.

As for removing the housing, it would require me removing the engine from the frame as the housing is one piece that wraps around the drive shaft. I could open it up and remove the other shrouds, that may help, but even then the carbs and the intake manifold setup allows for some coverage. I will think of a way to mouse proof it over the winter.

I get quite a dew mowers with horizontal engines & shaft dives offered to me for parts because they have a magneto / wiring problem & the owners could not face the hassel of removing the engine to get the cover off.
A lot of them end up having cooked heads because they were never cleaned and the fins were chockers with dry grass &/or mouse nests .
Because of the difficulty most work shops want 3 hours of labour just to diagnose the problem so most people buy a substantially inferriour mower with a cheap & nasty vertical shaft engine .

Good news everybody! She runs! She's a little cranky when cold, have to run half choke for 4 minutes or so, but once she is warmed up, she runs solid now, no misses or surging. And magically, I was able to finish without any extra bolts lying around making me nervous

One thing I found out, is that this engine gets HOT fairly quickly. After about 6 minutes, I could no longer touch the valve cover. It should not be an airflow issue, as all the fins are pressure washed and blown out with an air compressor. Now I just need to wait for the valve cover gaskets to come in to stop those from seeping all over the heads when I mow.

Thanks for all the advice!

Glad to hear the good news. Most guys never let us know the results.

bertsmobile1 said:

Finally fins should be cleaned annually

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Amen to that.....

Got the gaskets in and mowed the yard. Motor was solid, and the power was up. Before, I'd engage the PTO and the motor would almost stall. Now it is nice and strong, did not sound like it would get near stalling.

I will say, I parked it and shut it off mid Mow to move some stuff. About ten minutes. When I came back and started it, it surged a little bit for 30 seconds. Similar but not nearly as bad as before, and it cleared up quickly. I'm hoping that is more coincidence than an ongoing issue. We will see I suppose.

XTwarrior1985 said:

have to run half choke for 4 minutes or so, but once she is warmed up, she runs solid now,

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4 minutes sounds a little lengthy. Especially in our 95 degree weather we are having. Sounds like a partial pilot jet clog. I would boil clean the carb.

XTwarrior1985 said:

One thing I found out, is that this engine gets HOT fairly quickly. After about 6 minutes, I could no longer touch the valve cover.

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This is why I preach on here to CLEAN YOUR COOLING FINS AND BLOCK AREAS. Also it's in your engine manual as a MUST, yearly, to-do item.