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My mtd 22" cut makes a loud knocking sound when I put the engine under strain(cutting high grass)it shouldn't be a rod knock because I just Bought it 2 years ago and I have always changed the oil in it with pennzoil SAE 10W-30 platinum synthetic ( high quality oil) the blade is not loose so I have no clue what it is. It sounds like someone beating on metal with a hammer really fast. To be honest it sounds like a rod knock but I just wanted to see what y'all had to say

Sometimes the blade adapter (if equipped) cracks and will knock even though the bolt is tight. If your mower has a blade adapter, disconnect the spark plug wire, tip the mower with the carburetor up, remove the blade & adapter and inspect carefully. Replace parts as necessary. Also, check the engine mounting bolts for proper torque. Hopefully for you, one of these tips will fix your mower.

Lawnranger said:

Sometimes the blade adapter (if equipped) cracks and will knock even though the bolt is tight. If your mower has a blade adapter, disconnect the spark plug wire, tip the mower with the carburetor up, remove the blade & adapter and inspect carefully. Replace parts as necessary. Also, check the engine mounting bolts for proper torque. Hopefully for you, one of these tips will fix your mower.

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Thanks a lot for the tips. I will try it and get back on here with the results

Ok I checks all of that and its all good, still knocks.

Ok I check all of that and still knocks

Sounds like it's time to open the engine and find out where the excess clearance is. Rod to crank or wrist pin to piston/rod perhaps? Something else coming apart in the engine? Without the ability to hear the knock it's difficult to diagnose through email.

This is something that might help you lawnranger, when its. Cold, and I first start it, it knocks six times, it starts, and knocks 6 times. Not five or seven...six. its weird

chevyman984 said:

This is something that might help you lawnranger, when its. Cold, and I first start it, it knocks six times, it starts, and knocks 6 times. Not five or seven...six. its weird

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Live with it or tear into it.

Well then! I was just telling you!

chevyman984 said:

Well then! I was just telling you!

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I appreciate you telling me. No offense meant, I was just saying that from here you have two choices and I guess I didn't choose the best way of saying it. Sometimes I use the least amount of words to express my meaning and it can be taken the wrong way. I'll rephrase what I meant: Since the blade, blade adapter and engine mounting bolts are all in proper order you can use the mower as it is and see how long it will last or you can disassemble the engine to look for the possible cause. I've not heard of something causing a knock other than a loose blade/adapter, loose engine mounting bolts or excessive clearance in the connecting rod to crank or wrist pin to rod/piston. I'm not saying that there isn't or couldn't be another possible cause, just that I haven't heard of anything other than the items I mentioned. I'd sure like to be aware of another reason for a knocking sound such as you describe if there is another reason. Please post the cause if/when you find it as we all can learn from this situation.

Hi everybody, I'm so sorry it took me so long to get up on here, we had a real bad storm up in nelson county and knocked out power for 5 days. And after the power came back on, the phones and internet was down for several days too. Also dealing with insurance tha wont pay fora big oak tree that fell over on my suburban. So yeah sorry. And thank everybody for the help!! And I was joking so I knew you werent being rude lawnranger

Mine knocked on startup too. About 6 knocks!
1. Disconnect spark plug lead.
2. Tilt mower back to work underneath.
3. Clamp vise grips on crankshaft above blade mount.
4. Grab vise grips and blade and work blade back and forth.

Any play? Mine had about 1/2 degree of play. I tightened up the blade mount bolt and the knock went away. I put on a new blade and blade adapter last year and it loosened up. I will use some of the strong type of thread locker. Sometimes a damaged blade adapter is the problem. Checking for play is the diagnostic tool.

On MTD push mowers you have a blade adapter with 2 aligning pins built in it for the blade to ride one. The MTD's also have a strap with the 2 locating pins in it. If you install the blade with out the strap it will shake, and vibrate. It the blade adapter has been damaged it will shake and vibrate. If the blade has hit things the adapter is usually gets broken or makes the blade loose and shake.

ampman said:

Mine knocked on startup too. About 6 knocks!
1. Disconnect spark plug lead.
2. Tilt mower back to work underneath.
3. Clamp vise grips on crankshaft above blade mount.
4. Grab vise grips and blade and work blade back and forth.

Any play? Mine had about 1/2 degree of play. I tightened up the blade mount bolt and the knock went away. I put on a new blade and blade adapter last year and it loosened up. I will use some of the strong type of thread locker. Sometimes a damaged blade adapter is the problem. Checking for play is the diagnostic tool.

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