How to replace a sheared flywheel key on a Briggs & Stratton walk behind lawn mower

Visit www.thesmalleng...
*Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.*
This video shows how to replace the flywheel key on a Briggs & Stratton walk behind lawn mower. The engine is a Briggs & Stratton single cylinder, 650 series, L-Head engine. The procedure is similar on other brands of engines.
Sheared flywheel keys are a common problem on lawn mowers that have the cutting blade connected directly to the crankshaft. The problem happens when the cutting blade hits an object of large mass. This impact usually causes the engine to stop turning. The sudden stopping of the engine causes the rotational energy in the rotating flywheel to be transferred to the flywheel key and the key shears. The flywheel key is designed to shear when this occurs to prevent the energy in the flywheel from being transferred to the crankshaft and causing serious damage.
The method I used to loosen the flywheel from the crankshaft is not recommended by the manufacturer, but it works if you know how to do it. You need to be careful, because using the pry bar can damage the crankcase and hitting the crankshaft with a hammer can also cause damage. My first choice would be to use a flywheel puller, but the holes on this flywheel, used to attach the puller, were not threaded, so using a puller was not an option. Also, most people don't have the specialized tools recommended by the manufacturer.
Tools used to change the flywheel key:
- 15/16" Socket for the flywheel nut
- 3/8" Socket
- 5/16" Socket
- Strap Wrench
- Torque Wrench
- Pry bar
- Phillip Screw Driver
- Small Ball Peen Hammer
Specification:
- Engine Model Number: 124T05
- Tighten flywheel nut to 55 ft.-lbs
Flywheel keys can be purchased at your local small engine shop and online.

[@IPullingTractor]

You're a very smart man, to mention that the tapers on the crankshaft & inside the flywheel needs to be thoroughly cleaned and dried to prevent dirt or debri from causing the flywheel to slip on the crankshaft, which would easily allow the key to shear again. After professionally repairing various makes & models lawn mower engines since 1982, I learned A LOT about these things!

[@radicalman33]

Thank you so much for this great video. I brought my lawn mower in to be serviced, it just stopped working one day. The place said they had no wait and could work on it right away. I told them i put new oil, gas, spark plug and had cleaned the carb. A week later they still had it and said they were working on it. 5 weeks later they still had it and said they were trying to figure out what was wrong. i demanded it back, took it home and followed your video. FIRST PULL! saved me a lot of money!

[@levettabrown689]

This is awesome. Im a single mom with an awesome lawnmower that my son uses to work in the summer. I think this helped! It's the most understandable video so far. Hopefully you'll do something on the older bs models soon. Thank you

[@TechnoTinker]

Thank you! This never happened on my old belt driven mower, but my 2013 7.75 HP Snapper that I bought used developed this problem today. Three screws, and my cover popped off to reveal a flywheel with shards of key, and a loose flywheel nut. While I was down there, I discovered the air filter hose wasn't attached, so this repair may save me from an even bigger one. The hardest part of this repair was locating the model number. Off to the parts store!

[@jamiewilcox5631]

Thank you so much!! This video was so instructional and clear I had my mower running in 30 minutes after 2 weeks of wondering what I was going to do!

[@robertcarter2516]

My father-in-law hit a piece of scrap metal that I tossed off the trailer right next to his house. This did the trick getting it back running. Thanks for posting this video. I used a tie-down strap as an improvised strap wrench. I just tied it off onto the mower push bar.

[@midnightslasher83]

Thanks for the video buddy. I followed your video step by step for my 3 year old Briggs & Stratton and it worked like a charm. I had never worked on any kind of an engine before so this was a great learning experience. It took me about 30 minutes from start to finish. The only difference was that I didn't need to use a strap wrench to remove or tighten the flywheel nut. I just held the flywheel in place with my left hand and cranked with my right. Thanks again!

[@FRANKSBESEK]

I always like to check KZbin for a look see on something I am unfamiliar with. Watching your video made the job quick and easy. A cakewalk, to be sure. Thank you very much for posting. Good common sense stuff and simplicity. Have a nice day.

[@kemhayes6485]

One of the better instructional videos I''ve seen on KZbin. Thanks a lot. Well done.

[@gregeaker7704]

I borrowed my father-in-laws lawn mower and hit something in the ground it sheared the flywheel key I am poor I was about to sell stuff to buy him a new one and I saw your video watched it and found the key. Thank you vary much for passing your knowledge to help others there are not enough good people like us left in the world thank you vary much

[@TonyWesley]

Thank you for posting this video. I have a craftsman lawn mower with a Briggs & Stratton. The lawn mower hit an old meter fence post, which destroyed the blade. I replaced that but it won't start. Next thing to check is the flywheel key. Now I know how.

[@kashk818]

You are an AWESOME Man !!!! I followed your Video... And fixed my Pulan Mower.... Wish you all the success...

[@carolglinn7961]

Thank you!! I used the tip you gave for removing the flywheel without an impact wrench-worked perfectly!! Mower is up and running!! Can't say thank you enough-very clear and easy instructions, I had no problem following them. Thank you!!

[@ricknielsen6]

Thanks for taking the time to make this video. Saved me a bunch of money and my mower works great again.

[@richardalexander7089]

Slightly longer video than the others suggested but WORTH every second! I learned two new tricks! Thank you!!!

[@Mr_Tecumseh]

Thank you, someone who tells you what to tighten the flywheel nut to on a quantum. Best flywheel key replacement video I watched out of the 3, it gives the information you need. THANK YOU!

[@MM-sb1gd]

Thank you, sir! You are doing good and selfless work. This information comes as a blessing!

[@StevenHelen49]

Thank you so much for taking the time to put together such and excellent instruction video on this subject. The audio was great and the instruction was thorough. You saved me $60. You’re a blessing!

[@robertnicholls929]

Very good video. Easy to follow. I have done everything to get my mower to run but nothing worked. I saw this video and watched it and sure enough the flywheel key was sheared. Thank you.

[@MsRmaclaren]

Excellent video, I have a Briggs and Stratton 6.75 HP. Very similar. This video saved me a trip to the small engine mechanic. Thank You!!!

[@IrishNoiseMaker]

Thanks for this video. I had hit a stump with one mower and bought another used one a couple days later. Then started searching how to fix the old one. Saw this video and figured I'd try it. Couldn't find any 'keys' local so ordered from HD ($2.97 delivered to store for 3 of them which was 1/10th the price from sears). Keys came in 3 or 4 days later and within an hour I had the mower running again. Now I have two mowers working so I'll be able to sell one of them!

[@raybrickey3048]

Very clear and helpful video. Had been a long time since I'd done this on a much older mower. I had a package of 4 shear keys in my toolbox that I'd bought in 1991 for $1.41 at the local hardware store. I used 1 of them then and used a 2nd one today. Still have 2 left. lol Thanks again.

[@smallengineshop]

Thanks

[@sandygirl7193]

You are the best I've watched a lot of these videos and you should have a class 101 flywheel key removal... :-)

[@TheShoreman1]

Very well demonstrated. You got yourself a subscriber. Of course, if the key is actually sheared and the engine has been in the weather for a while; The flywheel would rather break in half than come off. Even if you pry and tap the shaft and then cut threads and use a puller. C'est la vie.

[@cleveaaj]

Good job! One of the clearest videos explaining the process.

[@smallengineshop]

Thanks

[@09hoseclamp]

yes, thanks for the video. your tip on how to get the flywheel off with just a pry bar and hitting with the nut slightly above the crank is a time saver when compared to using a 3-prong puller over the flywheel. i'm going to do that next time.

[@revilbam]

Been a while since I've replaced a shear pin. Your video helped. thanks.

[@gd8610]

Perfect! Thank you deeply for this video. Exactly what I needed. Well produced. To the point and explained well.

[@peterblack2670]

really, really appreciate this helpful video. As this seems to be a regular occurrence in my yard with all the rocks, roots etc... This video is a life saver...

[@charlesrankin570]

This worked great! Thank you for the video! I had replaced my carburator, new fuel, new oil, and still not working. Almost ready to buy a new lawn mower... Mine was sheared in half with flakes of metal all over which I saw after removing the flywheel. Had it back up and running 15 minutes later.

[@smallengineshop]

+Charles Rankin Good to hear! Its much cheaper to replace the flywheel key than buy a new mower...

[@Anhanga_frfr]

Be careful with that, though - I just found out the hard way that if you don't tighten it down pretty tight - you're almost guaranteed you'll be heading back over to where you got that flywheel key to buy another! Thanks @smallengineshop, this was super helpful!

[@nclarrync]

Excellent video, thanks. I had never done this before but you made it so easy I did it in 30 minutes. My flywheel did not come loose with your method, though - the pin was sheared and the crankshaft threads were rusty. However, I used a 3-arm puller which worked great.

[@richhenderson4821]

Excellent, the small engine shop had them in stock. Motor is back running, thanks for the helpful video

[@jimmywooten956]

Great instruction...you are a teacher for sure!! Pat youself on the back for a video well done.

[@tjjewell4115]

Very good instructions, keep up the good work with small engines, TJ

[@lking1260]

Thanks for this GREAT video!!! I've fixed mine twice now, would have been impossible without your video!!! I'm a subscriber!!! Thanks so much!!!

[@smallengineshop]

Thanks

[@michaeljdestefano1208]

Great job!! After your tutorial,I think I'm ready to give it a try. Thanks for taking the time to do that.

[@tsuchibutapotteryplants7491]

Thanks saved my brush cutter from the scrap pile.

[@PurpleHayzzze]

Thanks for the video man. Followed along and it worked perfectly. The flywheel was a bit stubborned to get off so I'm hoping I didn't damage the crankshaft or crankcase as you warned. Seems to be running fine though.

[@cheetoshane1378]

Thanks a million for posting this great video. Replaced mine today and it's up and running. :)

[@smallengineshop]

Thanks for watching!

[@crdennis123]

Never mind earlier question on the size of the flywheel nut. I went and listened to your video again and you say what size it is ... 15/16". Still say that I wish ALL videos were this detailed!

[@joetoney3604]

THANK YOU. Once repaired, it started on the first try.

[@MattWinschel]

Excellent video, well done, simple and informative.

[@lorisiewert]

this was a great tutorial! thank you for taking the time to make it!

[@boondocker7964]

Great video, kind of boring for you, money saver for me, good job.

[@mckinzi1]

rather than screw up your crank threads you could take a 1/4-20 tap and put the threads in there. a Briggs flywheel puller uses self tapping bolts to do the job for you. fyi, just because you didn't mess up the threads don't mean the next time you do one you'll have the same luck. the Briggs tool is pretty cheap but if you already have a generic 2 hole puller just tap the holes....you'll like the results

[@strumpeteer]

Great Video. I needed a refresher course since I did this only once about 5 years ago. Thanks for the video. :)

[@crdennis123]

Wish ALL videos were as comprehensive and detailed as yours!! I have one question, though. What size socket do you use to remove the flywheel nut ... or is that a special sized socket like the one used for installing/removing spark plugs?

[@cjuarez3169]

For those people that don't have a strap wrench or a blade removal tool you can also remove the spark plug and insert some rope to bind the piston to stop the flywheel from moving. Once the nut is removed I grab the flywheel and pull up and hit it gently on the opposite side of where I grab it with a rubber mallet to pop it loose.

[@gregorybarr6112]

Well done on the video! I have a Husqvarna lawnmower and hope it won't present any difficulties not seen on your video. The mower won't start and I suspect that the keyway pin is sheared as the last thing it did before coming to a halt was hit a rock.

[@smallengineshop]

Thanks.

[@homewinemakingvonsch]

Great video...clear and concise. Made the job easy-thanks!

[@smallengineshop]

Thanks

[@r3p3nt44giv3n3ss]

***** The bigger bolt on the bottom side of the fuel tank. I over-torqued that bolt and now it wont thread at all. The tank is held down by three other bolts, so can i get by with just three? Or do i need a whole new mower for just 1 bolt missing?

[@smallengineshop]

You might try repairing the threads.

[@r3p3nt44giv3n3ss]

***** You were right, the threads are worn. Also, what size are the bolt or nuts on the blower housing, i have a ratchet set and only one size almost works but its a little to big. Its labeled 8(and 5/16)

[@petecraterxxsulpnb5404]

Perfect video , easy to follow along , thanks

[@3beltwesty]

Puzzle for Experts Here!; Mine has the flywheel key with NO damage, but the engine after hitting something violently runs at HALF the rpm unless I really add another spring to force the throttle open!. It is an 2009 Ariens ST 622 String Mower that has a V belt drive to the jackshaft that holds the giant weedeater type "string" . I was cutting up crap after a Hurricane storm surge and the belt/string caught a piece of rope I did not see. The motor stopped what it seems instantly. After cutting out all the mess of rope I could start the engine but it only runs half speed when the throttle cable is fully to fast. It is pushing correctly at the carb. The only way to get it to run at a high rpm is to pull on the throttle at the carb. All the stock springs are there, nothing (outside) appears bent. One can disconnect the throttle cable and that is not the issue. Thus I added another spring that tugs like mad at the carb area, but it still is not fully up to speed. Thus I saw videos like this and pulled the flywheel and the key looks perfect. The old key and new one look and measure the same. For good measure I replaced it anyway and reassembled the engine and it does the same thing. **Could the crankshaft be twisted so the timing is wrong with respect to the crank throw ie piston? The engine is a 122L02-0012-F1 built in 2009; a L flathead 12 cubic inch 625 series 190cc **The engine acts like the governor is biased wrong, ie thinks the engine is going too fast. Thus I ponder if the violent stop goofed up or bent the governor inside "guts" or its shaft or cranks. The goofy thing is so many experts told me it had to be the flywheel Key and it was not. The engine had less than 10 hours on it before the accident. It is not a carb clogged issue. Any help would be welcome before I place a HF Predator engine on the beast. The entire life change of running slow was due to the rapid stopping of the engine. The string mower drives a belt and the pulley ratio is about 1:1 The rope did get all caught at the both pulleys, thus the engine stopped rotating just like hitting something hard. I have tried new flywheel key and new springs at the carb governor area and it still runs slow The coil's laminations to the flywheel's magnet timing looks correct to others on the web who show good and sheared keys. Stumped.

[@me373]

thanks for this video man I really appreciate the time you took to shoot it. very clear and direct to the point. the little tricks with the strap wrench and "bumping" the crank to remove the flywheel was worth the price of the whole video :) is that an oil filter strap wrench or??? just curious tho, how many "bumps" would the crank take before you might damage it? or would it ever be likely to damage it? sorry for the dumb questions. thanks again.

[@GarveyMustangMan]

Great video, very helpful, mine was running rough, but now the flywheel wont even turn, i believe the key is stuck in there

[@rmromanko]

If you don't happen to have a strap wrench, it works just fine if you unhook the spark plug, put on a leather glove, and hold the end of the blade while backing off the nut. I do like the trick of tapping the shaft, but as you already mentioned, a soft-faced hammer would be the better tool. It's also a good idea to put a piece of pine or other soft wood over the nut as well for extra insurance.

[@johnsprague1755]

Hi, That was easier than I thought after I saw you do it, the one question on that particular engine is what timing marks to use underneath, I'm assuming that I am to match up the plastic gear on the camshaft that has the 2 hash marks with the the hash marks or line on the crankshaft, John

[@TiTAMYRAiNBOw]

Great refresher thanks. what about weed eater flywheel removal? ??

[@MrHundredproof]

Nice vid very technical help me a lot thanks hope to see more fix it vids from you.

[@dicemanization]

Great video, start on 1st try -Thanks!

[@Bassman018]

Allot of engines don't have threads in the holes. you just find a bolt that is similar and start to thread it in, the aluminum is soft enough to allow threads to be made.

[@abstractduk]

great vid-exactly what i was looking for! just wanted to ask something. i hit a drain cover and felt the knock at the time. the mower carried on for probably around 15 hours before cutting out.. cutting out again before it finally died. when trying to pull it over i could feel something locking very hard. i imagined a valve locking against the piston. is this possible even? was just about to start looking at the head when i thought of the woodruff key and found your vid!

[@honor51]

Nice description. I've got a similar engine with flywheel removed. Inspection confirmed that the bearing is not holding the crank tightly, thus oil leaks there. Can you direct me to instructions to remove the bearing. Maybe some people refer to it as a bushing. cheers.

[@mattseymour8637]

Very informative video, good step by step guide. Looks a bigger job than i thought. Would you know if the shear key was broken by the lawnmowers performance?

[@smallengineshop]

Thanks. The mower won't run right with a sheared flywheel key. Throws the timing off.

[@travisclark1430]

Great video. Thanks, man!

[@smallengineshop]

Thanks

[@leeb.7188]

I took my BS 6.5 apart; cleaned carb, changed all fluids and spark plug; cleaned under-carriage. Still won't start. The rope pulls only about 12 inches and stops. Should I check for a sheared key first or a problem with the rope? This is my first time working on something mechanical so ANY advice would help a lot. Thanks!

[@antonjames8405]

GOOD VIDEO ,,I CHANGED the pin but as soon as I start it ,,,and it does start ,,, it breaks again ...I have broken three pins ,,,there is someting else that's wrong ??..help??..

[@XRayCam]

YOU SHOULD "ALWAYS" DISCONNECT COIL WIRE OR REMOVE SPARK PLUG WHILE WORKING ON THE MECHANICAL PARTS OF A LAWN MOWER. THEY CAN SOMETIMES START UP AND CAUSE INJURY OTHERWISE....SOME HAVE OTHER SAFETY MEASURES TO PREVENT STARTING - BUT NOT ALL.

[@107649365]

Stfu Nancy!

[@lebleb1972]

Yeah don't think that push mower will start on it's on. But good advice for something battery powered with a starter !

[@austincovey8790]

Small Engine Shop after doing this I'm having some kind of misalignment between the cable crank in the blower housing and the piece on top of the fly wheel. The little wings that stick out of the blower housing are slipping when they try to grab the piece on top of the fly wheel and I was just wondering if you had any advice on how to fix that? Thanks!

[@cw4mull]

Great video, helped alot. Thanks

[@smallengineshop]

Thanks

[@QuallsKen]

My Brigs and Stratton push mower is hard to start. The flywheel key is not sheered but the flywheel is stiff and hard to turn. Has plenty of oil but not too much. Gas is good, new sparkplug. It often takes several pulls to start mower. Any suggestions?Runs good once it starts.

[@johnlove9187]

This was helpful. Thank you.

[@smallengineshop]

+John Love Thanks for watching!

[@spike19581]

Excellent very helpfull. Thank you sir.

[@chelseacrumpacker8142]

What else can you use to loosen the flywheel safely?

[@d46512]

Thread the blind holes in the flywheel with 1/4"-20 tap.

[@stickstone1]

I do landscaping for a living so when the flywheel key breaks in two is that pretty much true for all mowers

[@smallengineshop]

Yes, it is a common problem on push mowers.

[@BushcraftingBogan]

I wish I would have saw that technique on removing the flywheel before I had to double my blood pressure meds! ;)

[@honor51]

@smallengineshop - Many thanks.

[@ross4329]

when i try to start my machine up (its a 650 series easystart) it doesnt start i only hear some clicking noises when i try to make it start does that mean my flywheel has sheared? i just changed my carb last year at the end of summer?

[@rameshm2100]

how would I know that the flywheel key is sheared. a chunk of wood got stuck in riding lawnmower deck pulley and now when i go to start it, I hear the noise but the fan doesn't spin.also would the riding lawnmower have the same flywheel system?

[@RhinoXpress]

i hopae that's the case for mine i huit something the blade of bent the mower started shaking an then when i replaced the blade it shook a lot less but still shook. hoping it's the key and not the crankshaft itself.

[@flyhieght]

This is good but we still can't get it off? Any help?

[@sergeiialovoi9727]

Thanks, good help.

[@Provic90594]

Hey l have a small 49cc engine that is hard to start, and when I do, it backfired, do you thinly its the flywheel key? I've been told that the timing is wrong, but these small Chinese engines don't have timing do they? Please let me know.

[@vlocity3]

can anyone recommend a good material for the key? I have a B&S motor mounted on my go-kart, and this key is the last step, I made a little aluminum one but my dad sais it will jsut shear when im driving around.. any tips?

[@swedish_brick_enjoyer]

The hammer and pry bar method will not work if the key is sheared.

[@RhinoXpress]

@smallengineshop i tried knocking it loose but it aint budging.

[@trevorb4949]

Awesome! Thanks.

[@mckinzi1]

go to a Briggs shop....the keys (not pins) are a coupla bucks apiece so buy an extra if you are stump happy with your mower.

[@TheRooster602]

ebay or Amazon. Read the comments by the people who bought it and you will learn a lot.

[@Oat57]

Good video. What I did was smack the shaft with a big soft hammer instead of a ball peen hammer.

[@richhenderson4821]

I contacted Sears to buy a replacement shear pin and they do not sell them. Does anyone know where to buy a replacement shear pin for a Briggs and stratton Craftsman pushmower?

[@ooblar7]

Where could I buy a shear pin?

[@me373]

@smallengineshop thank you again for the additional info friend :)

[@coolbreezz1952]

Thank You !.. :)

[@jaredelliott3267]

Anybody know where I could find the key for this motor?

[@minbenjalinfrank7728]

Go to any small engine repair shop. Got mine for a $1.00 today. This video was top quality. Kudos to the people performing the repair, doing the video and the great commentary with the tips.

[@gantmj]

6:23 I always clean the end of my crankshaft after I get it off.

[@smadas12]

Basics, Basics, Basics, You should have disconnected the spark plug lead before you even started. Think safe

[@StevieRich]

This doesn't work if your key is jammed and twisted

[@666mrjimbo]

know doubt iwas about too comment on that safety first