which blade on my Push Lawn Mowers do I needed?

[dogdog]

Needed to change the blade on the lawn boy 21" Lawn Mower... Yes some one mow rocks with it... it's missing chunks on the blade.

1) is that bolt left handed bolt or just a regular bolt ?

2) if the mowers says 21" lawn mower so this is a 21" replacement blade right I forgot to get the pic of the model number of that mower before I left, it have the number 1411384 I think that is the model number.... ?

3) Do I needed a special hold down jig or a 2x4 or monkey wrench and impact will do ?

The Kohler engine is fine, starts on first or second pull... not an issue..


This should be the manual, but I don't think anywhere it mention the part number for the Blade , almost useless other than the oil info and the torque for that bolt 82nm or 60 ft-lb.

https://images.homedepot-static.com/catalog/pdfImages/1b/1bf63a06-be4d-4e23-8b00-3d785e9abce8.pdf

 

[shoeless]

I can't help with the blade choice.

I have only change my blade once and I used my impact to remove it. I recall used a piece of wood to block it in place.
Have always been pretty nervous about changing them as my dad's friend had an accident doing his when I was a kid. Apparently the bolt broke loose on him or the wrench slipped, but either way he hit the back of his hand on the blade and it severed several tendons. I remember him talking about the doctors/nurses having to pull the tendons back out of his hand so they could be reattached.

 

[rancherbill]

It's a normal twist on the bolt. There is no magic in the part number. Get one that looks like mulching blade in the manual or the one that you are taking off.

The MAGIC is getting the right size hole in the blade and on some blades they have funny holes. Take yours off and measure and then go to the store. John Deere for example has a frilly edge on the hole.

 

[jhn9840]

I just put a C-clamp along the edge of the deck so the blade can’t spin when you twist the bolt off the blade.

jhn9840
John

 

[bwringer]

I just put a C-clamp along the edge of the deck so the blade can’t spin when you twist the bolt off the blade.

jhn9840
John

Yup.

There are also special clamps intended specifically for removing mower blades. Usually under $10.

Or if you have any of those big wooden woodworking clamps, those work as well and tend not to mar the deck, if you care about such things.

I usually zap 'em off with a 3/8" drive impact. Keep yer mitts out of the way, and they'll almost always zap off without bothering with clamps.

Finding the correct blades is a bit of an *** pain. The "correct" blade of the same part number will be ridiculously expensive and rare. So head to a big box home center and rummage until you find one that's compatible with your mower's mounting style, mulching capability, and length.

Use antiseize on the bolt when you install. Pull the mounting widget off the crankshaft (if you can; they're often corroded permanently in place) and goober it up with antiseize too.

 

[four.cycle]

^ Most walk-behind mowers use a 3/8-24 Grade 8 bolt to hold the blade to the bottom of the crankshaft.
That Kohler is probably metric - I don't know.
It should be regular right-hand thread - The only left-hand thread bolt on a lawnmower crankshaft I know of is on an old (1950s) 5S Briggs & Stratton engine, and those are pretty rare.
Find the correct blade for the mower. I don't see that many "Lawn Boy" models so I don't know if they use something specific to that brand, like Snapper or Toro.
Not really a good idea to put anti-seize on the blade bolt - they can back out and wreak havoc. Just put a drop of oil on it.
IF you can get the blade adapter off the end of the crankshaft (the "mounting widget" referred to in the above post), it's a good idea to remove it, clean it (and the end of the crankshaft) and put a dab of anti-seize on the inside cup of the blade adapter, but it's not necessary - there's generally no reason to remove it, and usually it requires a 3-jaw puller to get them off the end of the crankshaft.

New blade will run anywhere from about $15 (low end) up to $45 (what I paid for the last Snapper blade I bought with the wing kit.)
When you figure dollars per mile on the blade, it doesn't make sense to go cheap (or Mickey-Mouse it with the so-called "universal" blades that actually don't fit anything properly at all.)

YMMV

 

[dogdog]

It's a normal twist on the bolt. There is no magic in the part number. Get one that looks like mulching blade in the manual or the one that you are taking off.

The MAGIC is getting the right size hole in the blade and on some blades they have funny holes. Take yours off and measure and then go to the store. John Deere for example has a frilly edge on the hole.

That was the problem, I didn’t have the right tools 200 miles away. Just know some one mowed rocks and the blade have been damaged. So I won’t know the length since chunks are missing. I won’t know what pattern it was. All I got was it’s vibrating a lot. And you did a horrible job maintaining it, lol.

So now I am home, need to figure out what tools to bring before heading back. Figure lawnboy mowers might be popular some one must know if it says 21” mower is that mean the blade is 21”? Or it doesn’t correlate like that ? My bad that I forgot to snap a pic of the model number leaving in a rush. That user manual is horrible doesn’t mention anything technical like the ones I have for B&S small engines. But the engine is super good starts first one or two pull.

 

[four.cycle]

^ YES, a "21 inch mower" has a 21 inch blade under it. (Okay, it might be 19¾" or it might be 21¼", depending upon whether you're measuring it tip-to-tip through the bolt hole or otherwise... 21 is close enough.)
Blade bolts USUALLY have either a 9/16" or 5/8" head on them, but then again, that's for SAE - the only KOHLER engine I've had here was a Chinese-made unit and I had to go BUY more tools to get the damn blower housing cover off. (Extra long-reach "TORX" screws.)

I usually just tip the mower up on its side - AIR CLEANER SIDE UP, hold the blade with one (GLOVED) hand, and break the blade bolt loose with either an offset double-end wrench or a deep socket on a breaker. Sometimes you really have to lean on them if some jackass hogged the thing down too tight. It's a BLADE BOLT, not a HEAD BOLT. About 40 foot pounds is PLENTY.

 

[rancherbill]

OK, here's what I would do. A 21' inch blade fits a 21" machine". For the hole buy a UNIVERAL mount blade. This example will fit pretty well everything. it's more expensive but it solves your problem. Take a socket set, breaker bar and maybe a pipe. This has all the adapters. It's gotta be good it says EXTREME in the product name hahaha

https://www.canadiantire.ca/en/pdp/extreme-universal-lawn-mower-blade-21-in-0607148p.html

 

[dogdog]

ok thanks folks... I think I got the pic of it...

 

[dogdog]

All done, pretty simple with a chunk of 2x4 about 10 to 12” and impact.

Found the replacement at homedepot same as toro blade for lawn boy.

Also found that I am guessing the blade does not correlate 21” to 21” I guess… saw some 50” blades ? Shorter than this 21” blade. Weird.

Either case thanks

 

[four.cycle]

^ If you can find a piece of fence post or stop sign, a chunk of 4x4 works better to block the blade - it will generally slide right into the discharge chute.
Just sayin'.

 

[TobeyA]

Also found that I am guessing the blade does not correlate 21” to 21” I guess… saw some 50” blades ? Shorter than this 21” blade. Weird.

That's for a riding mower. A 50" would probably use 3 smaller blades. My 38" rider has 2 blades.

 

[woodscaper]

Also found that I am guessing the blade does not correlate 21” to 21” I guess… saw some 50” blades ? Shorter than this 21” blade. Weird.

50" deck, 3 blades side by side with a slight overlap.

 

[dogdog]

Yeah totally a new world for me with this blade stuff I would have expect a 50” to be 50” blade. Guess learn something new.

Next challenge will be the drive transmissions. Maybe next time when I go there again.

 

[The Cobbler]

cotton rope in the spark plug hole worlks well for removing blade bolts on mowers

 

[dogdog]

cotton rope in the spark plug hole worlks well for removing blade bolts on mowers

Not sure if that is needed. I found a blade remover jig thing in Home Depot also for $13. Not too bad if some one is going to mow rock a lot. I should take a pic of that blade.

I just remove the spark plug boot off the spark plug, lay some news paper and tip it on the side opposite to the air filter that was recommended in some YouTube vids. A short piece of the 2x4 is stand on the floor and the blade is rest on the other end. Install is the same with the wood block on the other side.

 

[Retctddvr]

I think you have it (21 inch blade for a 21 inch mower, except on multi blade mowers). I was happy to hear you mention pulling wire off the spark plug. I am surprised that wasn't mentioned in every post. Always disconnect the spark plug before trying to remove the blade on a rotary mower.

 

[bdbecker]

I was happy to hear you mention pulling wire off the spark plug. I am surprised that wasn't mentioned in every post.

I'm glad it got brought up as well. Sure, the handle safety lever *should* prevent an accidental start, but as easy as it is to pull the plug wire on most push mowers, it is not worth skipping this step. Just make sure to reinstall it when you are done.

My 6yo was hanging out with me while I was sharpening the blade this spring. After showing her the process, I could not get the mower to fire up. I was starting to get a little frustrated, checking the cables to the carb and fuel level. Right as I looked over and realized that I'd forgotten to reinstall the plug wire, she said "Dadddy, you forgot the spark wire!" While a little embarrassed that I had forgotten something so simple, I was very proud of my little girl for spotting the problem. I agreed with her that the 'spark wire' was the problem and thanked her for pointing that out. When the mower fired up on the next pull, she gave me a thumbs up and a big smile, and ran off to go play unicorns.

 

[65ranchero]

All this push mower blade talk jogged my memory.
True story:
In my other house I would cut the lawn with the rider and then finish the front lawn with the push mower.
My buddy had a mower that his father gave him ( his father. like a lot of us who curb shop) that mower was gifted to me.
His father told him it smoked and so he added gear oil ( boy did that stink)
One day my wife did the front lawn for me with that mower and comes in the house and tells me the mower stopped and that something fell off and shows me ( it was part of the aluminum block)
I go take a look and sure enough there is a hole in the block but the kicker was that when I moved the mower the blade was on the ground with the bolt and made a perfect 21" crop circle.
The best that I could figure is that the engine seized and the blade was still moving and wound it self off.

 

[four.cycle]

^ Probably snapped off the end of the crankshaft.
Good reason to NOT screw around with the baffle at the rear of the deck (that rubber thing hanging off the lower rear of the deck.)

I have never removed a spark plug or disconnected the plug wire when removing a blade. But then, when I'm doing tear-down, they're already drained of any fluids - it's not like they're going to start up on their own.

 

[imagineer]

Do you use a bagger, or mulch kit or just have the discharge open? It matters for what type of blade to purchase. If you are using a bagger, do not buy a "HI-LIFT" blade as it might disrupt the air flow that carries the clipping into the bag. If your running a mulch kit or open discharge, a "HI-LIFT" blade will be fine and actually help.

 

[four.cycle]

^ depends upon what the mower is designed to use. best thing to do is replace the blade with an OE type replacement. the "universal one-size-fits-all" units go into the scrap metal pile here. new blades (OEM type) right now for MTD/Bolens/YardMan - "about $26.00" (phone/KP/052622)

 

[csp]

I didn't read every reply, so maybe it's been said. Take the old blade with you when you go to purchase a new one. It's not like Lawn Boy blades are unobtanium. I have my dad's old two stroke Lawn Boy he bought in 1972 and have no problem finding blades for it.

 

[dogdog]

I didn't read every reply, so maybe it's been said. Take the old blade with you when you go to purchase a new one. It's not like Lawn Boy blades are unobtanium. I have my dad's old two stroke Lawn Boy he bought in 1972 and have no problem finding blades for it.

Yup I got it, they are the same as the toro 21" blades apparently sold at HomeDepot, it's a perfect fit, the adapter have a curve.

This lawnboy was sold at HD, then they discontinued it I think... not sure why. pretty good engine wise. But me not sure how these blade conventions are... figure get some quick answers on blade knowledge from the collective so I know what I am expecting when I am dealing with it. Besides that, I needed to know what tools to bring, 200+ miles trip is not a fun thing if you oops missed something at home.