I'm trying to get a Craftsman T100 tractor mower up and running that belongs to my dad. It was bought new in 2026, has been used a few times, but has sat idle through most of spring and summer. Are there other points I can troubleshoot quickly that I haven't looked into.

-Replaced dead battery
-Turns over strong and cranks, but will not start
-Solenoid in fuel line clicks with key
-gas in tank and flowing well through in line filter
-not flooded
-has oil
-not hydrolocked
-Filter looks clean
-inspected and reinstalled spark plug, but did not test

Is there anything else I can check or handy fault isolation steps I can do quickly before I get into more complicated fixes?

I appreciate your help.

Thanks for the help. I'll start with carb cleaner test, then move on from there. Dont have a spark plug tester.

In addition to the above suggestions, I'd empty old gas out completely and put new ethanol free gas in.

Are the ethanol remover products worth anything or just hype?

They help, but think of it as renting a bit of time. I use regular gas (with stabilizer) in some machines, but only ones I use a lot. Then I empty gas at end of season, if any is left.

For machines that I don't use all the time (and all 2 cycle engines), I use ethanol free gas.

tu ag said:

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They help, but think of it as renting a bit of time. I use regular gas (with stabilizer) in some machines, but only ones I use a lot. Then I empty gas at end of season, if any is left.

For machines that I don't use all the time (and all 2 cycle engines), I use ethanol free gas.

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Running the engine dry at the end of the season is the best way to keep things clean. The four easiest things you can do to keep a small engine running are:
1. Run ethanol free gas.
2. Running the engine until the fuel tank is dry if it's going to sit for an extended period of time.
3. Change the oil.
4. Clean the air filter.

Needs fresh gas. This is almost always the case for small engines that sit a long time.

GSS said:

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Gunked up, ethanol gas victim, is my guess.
Carb replacement....or you can try carb removal, blow out as many ports/orifices as possible. Ultrasonic cleaning, if feasible.

Will it fire off, if carb cleaner is sprayed into the intake?

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Are you a proctologist? Kidding aside, try this:

https://www.autozone.com/p/gumout-carburetor-throttle-body-cleaner-800002230/519569?productPartGroupId=16750&productBrandId=DXNH&productUniqueId=7923304882

I had a generator that wouldn't start. Sprayed it in the carb and it ran immediately. Thick smoke came out for a while. Sprayed it a few more times and it ran great.

Good suggestions above: fuel cut valve. Shut off and run it until the line is clear if not using if for a while. Ethanol free gas only.

Word of caution, the choke and throttle linkage on the T100 are atrocious if same as my ~2020 model. Make sure the choke is actually engaging and disengaging when it should and throttle is getting full range. Had to tweak a few times to get mine to work right after a few years use.

Through a couple hundred rebuilds, I can say with confidence that I've never had any luck with cleaners. The only cleaner I use is my parts washer, steel wood, emory cloth, carb wire of various sizes and straight up mechanical cleaning.

When you start cleaning ports and jets, I highly suggest just using straight carb cleaner from a can if you can before stuffing a wire of any kind anywhere. Doing so can damage jets and change port sizes which will screw up idle or high speed running. Also, wear goggles. I have had more than a few squirts of carburetor cleaner in my eyes and it's not a great feeling.

Then, buy ethanol free fuel, add stabil to it, and it will stay good for 2 Years or more.

Other advice above is good and I agree with adding a shut off if you can and running the machine until it dies at the end of the season or whenever it's going to sit a while.

You can take one more step and drain and wipe out the bowl after it sits for a bit. Some fuel is still going to be in the carb even after letting the engine die with a fuel cutoff. It settles back into the bowl and can gunk up over time, so that it can create blockages when you do try to start it the first time.

I am a crappy mechanic and hate doing it, but too cheap to pay someone else to do the work. So I've learned to take as many preventive steps as possible.

For most of the small engines I have had, I find it easier to just buy a new junk carb online than trying to fix the junk carb they came with. It looks like they sell the carb you would need on Amazon & eBay for $25-$30.

Malamute said:

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I'm trying to get a Craftsman T100 tractor mower up and running that belongs to my dad. It was bought new in 2026, has been used a few times, but has sat idle through most of spring and summer. Are there other points I can troubleshoot quickly that I haven't looked into.

-Replaced dead battery
-Turns over strong and cranks, but will not start
-Solenoid in fuel line clicks with key
-gas in tank and flowing well through in line filter
-not flooded
-has oil
-not hydrolocked
-Filter looks clean
-inspected and reinstalled spark plug, but did not test

Is there anything else I can check or handy fault isolation steps I can do quickly before I get into more complicated fixes?

I appreciate your help.

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Pull the fuel line and drain ALL the gas from the tank. Put it in another gas can (a gallon will probably work) and dispose of it.

Get a can of Berryman's B12 with a spray nozzle and straw and spray the heck out of the carb where the fuel goes in. I looked that engine up and saw a diagram but can't tell if you can remove the bowl. If you can, do so, spray as much of the internals as possible. If you just bought this, you won't need a new carb, you just need to clean the one you have. Leave the carb apart as much as possible and spray it several times.

Refill the gas tank with ethanol free gas and add the requisite amount of Mechanic in a Bottle. You might double the amount listed of MIB.

"Mechanic in a Bottle" WILL clean up some carbs, but it can take a day or two. Worst case, you're only out $10.

Before throwing parts at it, or taking to a shop, remove the air filter, spray some starting fluid (ether), and see if it starts/runs for a second or two.

Thanks fellas. I took off the filter and dosed it directly with starting fluid and it fired right up, but did not stay on or idle when adjusting throttle. Will remove carburetor and try to clean it out before replacing it. I'll throw on a fuel switch too.

Can you drop the "bowl" of the carb, without removing the entire carburetor? Sometimes, you just need to get a clear view of the needle/seat (spray a little cleaner in there) or work the float up/down a couple times (it can get stuck in place with crappy gas, and not allow more fuel to come in).

fburgtx said:

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Can you drop the "bowl" of the carb, without removing the entire carburetor? Sometimes, you just need to get a clear view of the needle/seat (spray a little cleaner in there) or work the float up/down a couple times (it can get stuck in place with crappy gas, and not allow more fuel to come in).

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Worth a try, but I usually see fuel able to reach the float bowl, but not pulled into the carb throat by air intake.

Had a similar issue with one of mt lawnmowers. I did everything you did above so I replaced the carburetor with a cheap Amazon model and that did the trick. Good luck.

Bowl cannot be dropped. Ordered a $20 replacement.

Malamute said:

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Bowl cannot be dropped. Ordered a $20 replacement.

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Right call. For some reason I can leave my mower full of gas all winter and the thing starts on the first pull come spring. My generator on the other hand won't start if I let it sit a month. I keep a spare Amazon carb on the shelf now and swap it out if I get in a tight spot when the lights go out.

AstroAggie15 said:

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HTownAg98 said:

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tu ag said:

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They help, but think of it as renting a bit of time. I use regular gas (with stabilizer) in some machines, but only ones I use a lot. Then I empty gas at end of season, if any is left.

For machines that I don't use all the time (and all 2 cycle engines), I use ethanol free gas.

---

Running the engine dry at the end of the season is the best way to keep things clean. The four easiest things you can do to keep a small engine running are:
1. Run ethanol free gas.
2. Running the engine until the fuel tank is dry if it's going to sit for an extended period of time.
3. Change the oil.
4. Clean the air filter.

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Also would add to install a fuel shutoff valve before the carb if its going to sit for long periods of time

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Yes, add a fuel shut off valve and shut the machine down each time by closing the fuel valve, it will burn all the gas out of the system each time, thus no fuel in the system to gunk up your carb again. My dad had a cattle sprayer for years, he turned it off by closing the fuel valve. It took a few extra pulls when starting but it always started and ran, I bet that engine lasted 15-20 years by shutting it off by closing the fuel supply valve.

New carburetor for 15$ and right as rain. Did the same for my ryobi weed whacker. Thanks for the input!