Exmark commercial 30" knocking

[Lawnboy18]

There is a knocking sound when I first start the motor at low idle, when and I shut it off and sometimes at the moment of engaging blades. It seems to come from the motor. Once the motor is running at max throttle, it sounds fine. Blades are tight, deck is clean, all belts seem fine and tight and the pulleys seem fine. I can pull up and down a bit on the crankshaft, but it has the same play as my newer 30" mower so I guess this play is normal. Any ideas? Oil level is fine, oil is nice and it doesn't smoke. Only at startup sometimes.

 

[bertsmobile1]

Lots of nasty expensive things can cause a knock inside the engine as can a simple thing like bad fuel.
So start with the easy bit, drain the tank and refill with some premium high octane fuel and see if it goes away.
Try running some heavier oil, if the knock goes away that means there is somthing loose or worn inside that needs to be looked at very soon.
Monitor it carefully, if the knock sounds like it is getting louder or longer then it is time for strip down or at least a visit to a good mechanic.

 

[Lawnboy18]

Hey Bert!

I think I have found the problem. I was using the mower and once I was done, it was facing me while I was closing the gate and I could see that the motor was moving a little too much while on low idle. I grabbed the motor with two hands and I was able to twist it and lift it up and down quite a bit. At the end of the day, I brought it in the shop and tightened the motor down the best that I could. I can still see some play (the bolt moves up and down a bit), but I cannot tighten it more. Could it be that grim and other stuff is in the bolt hole giving me a hard time to tighten the bolt more?

While I was working on the mower, a friend was talking with me and he spotted a nice big crack in the deck. What a nice end of season gift.

 

[gainestruk]

The one you can't get tight probably has worn the frame, you might try getting a flat washer and new bolt, I would put some lock tight on bolt to keep it tight.
It's really important to keep engine tight on frame, you can do a lot of damage in a short period of time.
You have a pretty good chance this is the knock you were hearing.

 

[bertsmobile1]

Pull the motor, weld up the crack build up the holes that are flogged out oval then weld some heavy washers underneath.
Old mower blades make real good bracing pieces but you will need special drills to make holes as the are usually Boron steel which like bulldozer blades work hardens
Die grinders can also be used but getting an accurate hole with one takes a reasonable amount of skill and mainly patience.

 

[Lawnboy18]

Thanks for the input guys! The mower is not even a yeard old. I bought it in March. I will bring it in under warranty. I hope they replace that cracked deck with a new one. Besides, the motor has probably banged around the deck causing some mishapes. If this is not covered under warranty, I will get it fixed myself.

The first question would be why did the motor come loose?

 

[gainestruk]

My guess and which I would also tell them it wasn't torqed to right specs when it was built, I've changed or rebuilt several 20 + year old equipment that have never been touched and had a heck of a time getting them out.

Hope Exmark steps up and takes care of this, please let us know how it goes.

 

[Lawnboy18]

That is what I am thinking. A mower made on a Friday in late afternoon. Of all the mowers I have had, none have had a loose motor.

Once my season is done (3-4 weeks), I will bring it to the shop for warranty. Hopefully, my backup mower that leaks oil will last (also new and bought in July).

 

[bertsmobile1]

Thanks for the input guys! The mower is not even a yeard old. I bought it in March. I will bring it in under warranty. I hope they replace that cracked deck with a new one. Besides, the motor has probably banged around the deck causing some mishapes. If this is not covered under warranty, I will get it fixed myself.

The first question would be why did the motor come loose?

Might not have been tight enough in the first place, they are after all noting but a modified self tapper.
Can also be operator thingd like running with out of balance blades.
Or even something like random engine balance
Did not notice it was new so yes strait back to the dealer.
However don't be suprised if they tell you take a walk as the operator is supposed to check all bolts for tightness.
It is in the owners manual that no one bothers to read and is a gret out of fixing free card for every mower company.

 

[Lawnboy18]

I hope they don't give me that excuse. I did do my homework at that. Thing is I can't tighten the bolt more... I could tell them that and it is being honest. I found the loose bolt and tried tightening it.

Once my season is finished, I will let you guys know if the dealer is willing to fix this or not. These mowers have not been abused.