Craftsman T1200 - Won’t Start

[Matnetik]

Long time listener, first time caller - watched every video I could find on YT and read through every post here and on Reddit and am looking for some help!

Craftsman T1200
Model: 247.203726
DOM: 02/2018

Purchased used from a gentleman that fixes small engines, said it was in perfect condition and running as it should. Looks almost brand new. I mowed my lawn three times with it, on the forth time I made it about 100ft and it stumbled and died. It will crank but won’t run. Below are the things I have done / checked-

Brand new carb (also took it out, completely disassembled, cleaned and rebuilt)
Fuel Solenoid is functional and clicks when the key is turned (also disassembled and cleaned)
New air filter with pre-filter
Fresh gas (93 oct)
New NGK spark plug
Added fuel cutoff valve and new fuel filter
Battery is less than a year old and fully charged
20A fuse is good to go
Compression is at 150
Oil is at the correct level and was replaced in July

No matter what I do it just won’t run or fully turn over, just spins and spins and spins. Any help or ideas on next steps would be beyond appreciated, a few weeks behind on my cut and a service tech can’t make it out for two weeks, would honestly love to fix it myself but didn’t want to dig into the engine if I don’t have to.

 

[SeniorCitizen]

As soon as it dies and won't start remove the air filter and put a teaspoon of gasoline in the top of the carburetor and try it .

 

[Craftsman Garage]

What engine is on the riding mower? We need the model number off the engine shroud. You have fuel, and compression which leaves air, spark, and timing. I would lean towards timing, so check the flywheel key and the valves. I bet the flywheel key is sheared. Maybe the valves came loose? I would also check for Spark because even though you replaced the sparkplug, the coil could be bad. I think this tractor has the chinese engine that can sometimes be finnicky.

 

[Matnetik]

First off thanks for the quick replies - will get the engine model number in a bit here!

I did forget to mention I tested for spark and can confirm it’s getting it via plug tester
I tried gas in the air intake as well as starter fluid with no luck
I also removed the plug and spun it a few times to clear everything out in case it was flooded

My initial thought after all this was the flywheel key (timing) and excuse my ignorance here but I have no clue where it is or how to check it, from my understanding i need to remove the plastic grate on top and get a puller to remove the flywheel to access the key?

I also found this number on the tag along with the model number I listed above - 13A278XS099

Good reference here I found -

and I believe this is the part - https://www.searspartsdirect.com/product/5b5p5lzaws-0071-247/id-951-10307

 

[ILENGINE]

Looks like this mower uses the 4P90HU MTD engine. Looks like compression is supposed to be 55-80 so I am wondering especially with the high compression reading if then valves are opening and closing properly. May need to remove the valve cover and inspect the push rods and make sure everything is opening and closing as it should.

 

[Matnetik]

So I can confirm it is the flywheel key, took it apart today and it’s not even in there. Where can I get one of those? Are they universal? Lowe’s? I can order them but given Asheville just got destroyed by Helene I doubt anything will arrive in a timely manner. Just wanted to ask if it’s a common part a hardware store would have, thanks!

Part Number: 951-10307

 

[mikekir]

Any good hardware store with those orange cabinets of stuff may have the woodruff key you need. The fun part is choosing the right one.

 

[slomo]

So I can confirm it is the flywheel key, took it apart today and it’s not even in there. Where can I get one of those? Are they universal? Lowe’s? I can order them but given Asheville just got destroyed by Helene I doubt anything will arrive in a timely manner. Just wanted to ask if it’s a common part a hardware store would have, thanks!

Part Number: 951-10307

Order extra flywheel keys and get the proper OEM torque value for the flywheel bolt. Most are a tapered shaft. Polish the crank end meaning remove no material, just polish and clean up. The inside of the flywheel needs cleaned up/polished too.

Some flywheels have a key that is kinda hidden until you remove the flywheel. Key is in a slot slightly down on the crank end. Once you get the flywheel off it will confirm it for you.

Nice catch on finding the missing key.

 

[Matnetik]

Order extra flywheel keys and get the proper OEM torque value for the flywheel bolt. Most are a tapered shaft. Polish the crank end meaning remove no material, just polish and clean up. The inside of the flywheel needs cleaned up/polished too.

Some flywheels have a key that is kinda hidden until you remove the flywheel. Key is in a slot slightly down on the crank end. Once you get the flywheel off it will confirm it for you.

Nice catch on finding the missing key.

Appreciate this! Ordered 5 last night just to have - will get things cleaned up before they arrive so it’s ready to go and report back - need to go to a few hardware stores today to fix things around the house so I’ll take a peek while I’m out for one!

 

[Matnetik]

Well got the flywheel off and no luck - the key is perfect. I thought it was the key from looking at the top. No idea where to go next with this one other than taking the valve cover off and inspecting, just seems odd that it would be an engine issue.

Battery is at 12.26v and is new, even connected it to my car with cables and no luck, seems like it doesn’t always want to spin.

https://www.dropbox.com/scl/fi/r5uy...sues.mov?rlkey=mfxq3i36fzzzeut384egkrw58&dl=1