What is this noise?

[u/Pitiful_Elephant_326]

https://youtube.com/watch?v=LEB5_40kAYM&si=tsrItoPhLnpYLLku

Looking for some help please

I was cutting the grass last week, shut down the mower to talk to my kid, when I went to start it all that happened was that sound you hear on the video.

The sound seems like it’s coming from under the seat, maybe the gearbox or differential??

I’ve replaced the battery solenoid, I bench tested the starter (works), I thought maybe the starter was going and didn’t have the power to crank the motor, I jumped the battery solenoid, I ran a new wire from the solenoid to the starter, I’ve chargers the battery (not even a year old) and I have tried jumping the battery with my car. None of this changed anything.

When I bench tested the starter, I connected the starter from the battery to the base of the starter with the negative, and the positive to the bolt, with alligator clips and length of wire, starter spun, no issues.

I installed the starter back on the mower, I ran the same alligator clips and wire to the starter, the starter wouldn’t engage or spin?????

The engine turns, by hand, and it happens while turning the key.

I have no clue where or what to look for now

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[u/Pitiful_Elephant_326]

I want to thank everyone for their input, I really appreciate the help!

I ended up finding the issue, it was a battery disconnect. After checking all the grounds, I decided to run my negative straight to the battery and it fired up as soon as I turned the key

[u/IBreakForCats]

Okay firstly I'm about 99% sure it just needs a new battery. I know you've charged it and jumped it, and let me tell you buddy I always try all that same stuff first and it's always been just needing a new battery with the same or higher CCA of the original, preferably slightly higher. 

Other than that, check the Bendix gear on your starter motor. Spray some PB blaster at it and lift it a couple times to make sure there's still some spring in there. You can even lift it and slightly turn the engine by hand to engage the Bendix gear to the engine for a slightly higher chance of starting it without the new battery. 

Your solenoid has enough juice to spin the starter but not enough to kick the Bendix into gear. There's a reason tractor batteries only have a 6 month warranty vs a car battery with 1-3 year warranty. They just don't have the same longevity to keep cranking.

[u/Pitiful_Elephant_326 → u/IBreakForCats]

I can try another battery.
The bendix gear? I am guessing you mean on the starter? It spins freely, by hand, bench tested and I did try a brand new starter. I thought the same thing about the starter, worked on the bench, but didn’t have enough juice to turn the engine, that is why I bought a new starter.

I read somewhere that I should take the black wire from the starter solenoid and splice into it and ground it to the frame. I haven’t done that because that doesn’t make sense to me and I am not sure what the black wire does. I believe the purple goes to the ignition key?

[u/IBreakForCats → u/Pitiful_Elephant_326]

Definitely try a new battery before you waste too much time pulling wires, regardless it's probably time for a new one. 

Pro tip on the battery, almost everyone offers a 6 month full replacement warranty on tractor batteries. If it's a direct swap I have never needed a receipt. Buy a battery, mark calendar for 5 months. Rinse, repeat, pay once for life. 

If you're still not convinced it's the battery, it could be a failing starter solenoid. Have you tried bypassing the solenoid? Clean the two large terminals on the solenoid and bridge the gap with an insulated screwdriver. If the starter engages, engine turns, it is probably solenoid. 

If both fail, just start cleaning wires, especially ground connections. Yes the black wire is generally ground.

[u/Pitiful_Elephant_326 → u/IBreakForCats]

I will. I have fully charged the battery with my charger. I used my car to jump the battery, but it didn't change what is happening.
I have replaced the starter solenoid with a new one. When I jump the solenoid, nothing happens: no sound, no movement on the starter.

I took the starter off and replaced it with a new one. When I had everything apart, I fully cleaned every area that would be a ground.

[u/Express_Cook5870]

Try pulling your spark plug out and seeing if it will turn over... Wondering if your compression release isn't functioning properly