The Right Way to Straighten a Bent Mower Shaft

   09.01.20

The Right Way to Straighten a Bent Mower Shaft

(Image: Screenshot from video)

Being an outdoors person often means using equipment to get stuff done… things like tractors, ATVs, UTVs, and lawnmowers. Knowing how to fix stuff goes a long way in helping a prepper (anyone, really) remain self-sufficient. Enter this video from a guy who knows his stuff about small engines and such.

His channel is Steve’s Small Engine Saloon, and I’ve come to respect this Canadian YouTuber, who sometimes comes off a bit wacky — but in the end, he has proven to be knowledgeable and experienced about the things in his videos. And we all know you can’t say that about every person who gets on YouTube to show people how to do stuff. He also gets to the point without a lot of worthless yakking.

Anyhow, back to the subject of this video, which is straightening a bent crankshaft on a lawnmower. Most of the time if a mower hits a rock or snag and gets bent, folks toss it in the trash… but the shaft can often be straightened.

To prep the mower, you remove the spark plug, disable the flywheel brake, tip it over (carburetor side up!), and remove the blade & adapter.

In his example machine, the shaft is really bent — so much so that I involuntarily said “Wow!” when he showed that to us at the 3-minute mark. Most folks would definitely consider this mower to be junk with a shaft bent that badly.

Machinists know how to use a dial indicator to make sure something is straight or centered, but if you don’t have one you can just copy his super-simple method involving a magnet and just about any steel object such as a spark plug wrench or screwdriver.

You slip a long stout pipe over the crankshaft and hunker down in his patented(?) shaft-straightening position, and get to straightening.

If you have ever straightened something, you know it doesn’t usually happen on the first try. Steve said it took him 14 bends (bend, check, bend, check, etc) to get this shaft trued up — but that only took him about 6 minutes. So it’s not an all-day deal by any means.

Is it perfect when he’s done? Not quite… but it is definitely much better than it was.

Why not use a hammer? Because you can ruin the oil seal, the engine bearing, or even break the engine block. There are all sorts of things that can go wrong when you apply a sudden shock to an engine… as I have learned by working on quite a few small engines myself over the years.

I use a push mower at my hunt camp and there are all sorts of things I might hit with the blade. Nice to know I can straighten up the shaft without a big hassle or ordeal if I hit the wrong thing with it.

Anyhow, I hope you enjoy the video.

Read More