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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.

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.

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.

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.

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.

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?

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.

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).

Lawnboy18 said:

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?

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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.

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.

I've got an update for you guys. I took the time to remove the bolt completely and found some metal shavings on it (a very bad sign). So, I used my wire brush on my grinder to clean the threads on the bolt. I then inspected the bolt hole in the motor and I could see that it was worn out. I tried removing some metal shavings with a small flat head screw driver. After the procedures, I was able to screw back the bolt on pretty tight. The motor is now secured down properly to the deck. I am going to run it for a while and see how it turns out. If not, I guess I am going to seek help and rethread the hole (I hope this is possible) or maybe warranty will cover a new motor

Lawnboy18 said:

I've got an update for you guys. I took the time to remove the bolt completely and found some metal shavings on it (a very bad sign). So, I used my wire brush on my grinder to clean the threads on the bolt. I then inspected the bolt hole in the motor and I could see that it was worn out. I tried removing some metal shavings with a small flat head screw driver. After the procedures, I was able to screw back the bolt on pretty tight. The motor is now secured down properly to the deck. I am going to run it for a while and see how it turns out. If not, I guess I am going to seek help and rethread the hole (I hope this is possible) or maybe warranty will cover a new motor

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Before you go any further or run any more I strongly suggest you take to dealer to check on warranty, if you keep working on it and running it I guarentee they won't cover damage.

FYI if they won't cover new engines come from factory with smooth bore on mounting hole, bolts are self tapping.
You could run a drill bit just big enough to clean up threads then go with a little bigger self tapping bolt, just don't take much off with drill, the thinner the walls it will lower the strength and could snap off.

I will not fix it more until I talk with the dealer.

You've said it, I'm screwed. The warranty won't cover because of the self tapping. Luckilly, I know some very good mechanics at a scrap yard. They can help out.

I feel your pain on the noise. I researched and read reviews on these things for over a year before finally deciding to spend the BIG BUCKS on one. I don't do lawn work for a living, but I'm all about buying things that are well built/made.
That being said, I bought mine in June, used it a total of 12 times, (changed engine oil after 8 times) and a deck bearing starting raising hell on it. I'll also mention that I'm very picky and take very good care of everything I own. (rinse and blow mower off after every use)
I took it back to dealer I purchased it from, they replaced the faulty bearing. Mower was 89 days old at this point. I go to pick it up and the lady at the counter says, "Your total today is 68.25". I said, I just bought this mower in June, she says Oh I'm sorry it's no charge. I suppose if I didn't say anything I would've paid.
Anyway, I took it home, started it up, engaged blades and HOLY HAYELL!!! The blade tensioner is rattling so bad, it sounds like a rod knocking. I will also mention that I've been an auto tech for 25 years and am very capable of working on all types of things. However, I paid 2k for this thing and it has a warranty!!
I took it back, as it obviously was not making this noise before. They adjusted the blade brake cable and attempted to charge my wife $40 when she went to pick it up for me. Needless to say, she/we didn't.
Got home, unloaded it off of truck today, started it back up, engaged blades and low and behold, noise is still there.
I will be making any further repairs myself and will never purchase another exmark product again. I will mention also, I have a Honda 21" bagger that I traded a set of screwdrivers and 100 bucks for, that I've used for 3 seasons without any problems whatsoever.

Seems like you have been unlucky.

That tensioner rattle is something recurrent on these mowers. If you look at it, the tensioner will wobble up and down just enough to hit the frame. It isn't anything bad as I can see. Both my 30" mowers do it and have done it for months doing 75-80 yards/ week. It can help to replace the BBC belt (every 250 hours). I will be doing some looking at that rattling and try different fixes for this. I am thinking a worn out bushing.