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Craftsman 21" 4.5 hp Briggs breaking blade adaptors


WTK1974's Avatar
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Join Date: Mar 2007
Posts: 15

04-06-07, 01:48 PM   #1  
Craftsman 21" 4.5 hp Briggs breaking blade adaptors

I have a Craftsman 21" pushmower with a 4.5 HP briggs engine that mulches and bags.

Last year, I hit something that caused the original blade adapter to break. Replacing the adapter and blade seemed to be a good idea, so I went to our nearby Sears Essentials to get new ones, but they were out. So, I went to a nearby hardware store. The person who helped me seemed to know what they were talking about, and told me I could use a blade adapter for a star-hole blade. So, I bought the adapter and blade.

Installing them seemed easy, and I got the bolt that held them on good and tight.

About 10 minutes into mowing, the mower started making knocking noises. I checked the oil, but it was ok. Turned out the blade adapter I just bought was breaking apart. I took it back and got another one, and it has broken as well.

Is this something that has to be sourced from Sears? Sometimes it seems like their equipment doesn't do well with universal parts.

Any advice and suggestions would be appreciated.

Thank you,
-Bill

 
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backyardwonder's Avatar
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Join Date: Jan 2007
Posts: 105

04-06-07, 02:02 PM   #2  
There is a lot of after market stuff out there for small engines, and just about everything else, that isn't worth the box it comes in and it would appear your blade adapter is one of them. I would order a replacement from Sears as much as I hate to say so but at least if it breaks they will replace it, (I hope).

The sole purpose of the star shaped hole is to oblige you to purchase that particular type of blade, exclusive to the machine manufacturer. They just don't want anybody buying generic parts if they can help it; they don't make any money if you buy somebody else's parts.

One other thing that comes to mind is the possibility that you bent the engine crankshaft when the original blade broke. If the crankshaft is bent, even the slightest, the vibration could prevent you from ever using that machine safely again. If you noticed any vibration at all after you replaced the blade, the crankshaft could be toast. It's hard to imagine a piece of steel as thick as a crankshaft actually bending on impact but it happens regularly
as folks go about their yards, especially in the spring, pranging into this, that and the other. This is a very good reason to always walk the yard before cutting just to be sure there are no foreign bodies lying low in the grass.

I hit a piece of rebar once that some kid, (I assume), threw over my fence. That was the end of that lawnmower.

 
puey61's Avatar
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04-06-07, 02:56 PM   #3  
Just another area to be aware of is if the blade bolt you purchased is too long and bottoming out before the blade is actually tight. In other words, the bolt hits the blind hole before making contact with the blade.

 
WTK1974's Avatar
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Join Date: Mar 2007
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04-06-07, 04:52 PM   #4  
The mower's crankshaft was bent, but I had it fixed at a small engine repair shop. Before I did that, it would shake terribly. I didn't know what was wrong until a couple of bolts vibrated out of it, and I took it for service. They wanted $180 to fix it, and I had only paid $150 for the mower new.

It runs fine, but that part broke. I'm going to visit the nearest full-size Sears tomorrow to see what they have in the line of blades and adapters.

Something I noticed is that the new blade looks alot different than the old blade. I didn't see any sign that the new blade was touching the deck or anything like that, and it's not as wide as the factory blade.

 
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