Hit a rock and now the mower shakes terribly

Hey everyone. I use an older riding mower around my bean farm, and yesterday I accidentally ran over a hidden rock in the tall weeds. The mower immediately started vibrating, and the grass looks completely uneven now. I looked underneath and one of the blades is definitely bent up pretty bad. I'm going to order some new lawn mower blades online to replace them both, but I've never actually taken them off before. Do I need a special tool to keep them from spinning while I loosen the bolt, or can I just use a regular wrench and a block of wood? Any tips for a beginner would be great.

Hey Rocky, it's pretty easy to pull blades off. Raise the deck and mower, if you can, to make for easier access. I have the drive up plastic ramps and they work well. It's a good practice to wear leather gloves to hold on to the blades to remove them but I've never worried about them, I just just don't hold where the blades are sharp. You can use a block of wood to hold the blades but I haven't found that necessary either. Grab a blade and an impact wrench if you've got one and loosen them up. A rachet will work fine too, and it may make the wood block more useful. My blades have a star shaped hole that lines up with the sprocket underneath, just make sure they are lined up when re-installing, if you have them.

Rocky38 said: Hey everyone. I use an older riding mower around my bean farm, and yesterday I accidentally ran over a hidden rock in the tall weeds. The mower immediately started vibrating, and the grass looks completely uneven now. I looked underneath and one of the blades is definitely bent up pretty bad. I'm going to order some new lawn mower blades online to replace them both, but I've never actually taken them off before. Do I need a special tool to keep them from spinning while I loosen the bolt, or can I just use a regular tunnel rush wrench and a block of wood? Any tips for a beginner would be great. Click to expand... I’ve changed mower blades after similar rock strikes, and I’d avoid relying on just a block of wood. First, shut the engine off, remove the key, disconnect the spark plug wire, and make sure the deck is secure before reaching underneath. A blade-holding tool or blade clamp makes loosening the bolt much easier and safer. Some people use a solid piece of wood against the blade, but you need to be careful not to damage the deck or let the blade move unexpectedly. Since you hit a rock hard enough to bend a blade and cause vibration, I’d replace both blades as you planned and also inspect the blade spindle, bolt, and deck for damage. If the spindle shaft is bent, new blades alone won't solve the vibration. Check the mower manual for the correct blade orientation and torque when reinstalling.

Plus consider left hand/right hand threads on the attaching bolts...

One more thing to consider. IF you have a lot of vibration like that, you may have bent the mandrel shaft. When you get the new blade on, pull the blade past a spot in the housing where you can sight across it. Then pull it around till the other blade goes by that spot. If the mandrel is bent, you'll see it. They are not too hard to change out.

aighead said: Hey Rocky, it's pretty easy to pull blades off. Raise the deck and mower, if you can, to make for easier access. I have the drive up plastic ramps and they work well. It's a good practice to wear leather gloves to hold on to the blades to remove them but I've never worried about them, I just just don't hold where the blades are sharp. You can use a block of wood to hold the blades but I haven't found that necessary either. Grab a blade and an impact wrench if you've got one and loosen them up. A rachet will work fine too, and it may make the wood block more useful. My blades have a star shaped hole that lines up with the sprocket underneath, just make sure they are lined up when re-installing, if you have them. Click to expand... Thanks for the advice, aighead! I ended up using my plastic car ramps to get better access underneath just like you suggested. I didn't have an impact wrench handy, so I used a regular ratchet and wedged a block of wood in there, which worked perfectly to keep it from spinning while I broke the bolt loose. Got the new lawn mower blades installed this morning. Mine did indeed have that star-shaped hole you mentioned, so I made sure to line it up carefully with the sprocket before tightening everything down. The mower is running completely smooth again with zero vibration. Really appreciate the help!

Good deal! I forgot about pulling the spark plug wire like @cerfrazzled mentioned, which is also good advice that I usually don't take. Theoretically, you can jump start the engine by spinning the blades around with your hand or a wrench. That'd make for a real bad day.

If it has the star shaped holes, that would make it a newer mower. That means it has safeties, unless someone has bypassed them. That means it also has an electric clutch or whatever, to engage the mower deck. I’m all about safety, when it’s required but honestly, I haven’t even bothered to look where my spark plugs go. This job is best with an impact gun, whether electric or air. The biggest issue, is making sure blade is flush to the shaft and not caught on the edge of the star edges. Rotating the blades, is part of the job. To verify the spindle is not bent but also seeing if the blades will hit. I ordered some blades last fall that lightly touched, even though they were spec’d for my mower.

Rocky38 said: Hey everyone. I use an older riding mower around my bean farm, and yesterday I accidentally ran over a hidden rock in the tall weeds. The mower immediately started vibrating, and the grass looks completely uneven now. I looked underneath and one of the blades is definitely bent up pretty bad. I'm going to order some new lawn mower blades online to replace them both, but I've never actually taken them off before. Do I need a special tool to keep them from spinning while I loosen the bolt, or can I just use a regular wrench and a block of wood? Any tips for a beginner would be great. Click to expand... A block of wood will usually do the job, and you don’t normally need a special tool. Just shut the mower off, remove the key, disconnect the spark plug wires, and make sure the blades can’t start turning before you get underneath it. Put a piece of 2x4 against the blade and deck to keep the blade from moving, then use the correct socket and a breaker bar or wrench to loosen the bolt. Keep your hands well away from the blade edge. Since you hit a rock hard enough to bend a blade and cause major vibration, I’d also check the spindle and blade mounting. A bent spindle can keep shaking even with new blades. Don’t run the mower again until you’ve checked that.

aighead said: Good deal! I forgot about pulling the spark plug wire like @cerfrazzled mentioned, which is also good advice that I usually don't take. Theoretically, you can jump start the engine by spinning the blades around with your hand or a wrench. That'd make for a real bad day. Click to expand... That's if the blades are engaged.

Be careful. I read this in an industry magazine back in the day. https://www.wired.com/2006/10/penis-to-arm-tr/ I clipped the magazine article and still have it somewhere.

Mike-G said: Be careful. I read this in an industry magazine back in the day. https://www.wired.com/2006/10/penis-to-arm-tr/ I clipped the magazine article and still have it somewhere. Click to expand... ??The article or the object the article was referring to????? I would assume if it was the second one you would remember!

Okay kids we learned something new today wait the 3hrs 55mins after taking Viagra before fixing the lawnmower.

Need to find another rock to hit, it will then cancel out the first one......

That's more my style DDoug.