Vibrations on my ZT34

[blue262]

Hi folks, new guy on the block. I really enjoy forums for just about anything I own. Okay to the point, I just purchased a 2018 Gravley ZT34, with a 6000 series Kohler motor. It was somewhat abused, ( oil like mud, belts and blades never changed or sharpened or at least 6 years) after all that abuse the motor is still strong after tune up oil changed bad fuel removed. After cleanup and new blades and belts and a new mulching kit, I am getting a strong vibration from the mower deck, I check pullies and grease fittings, but can't tell where the vibration is coming from, I know there is more troubleshooting I can do but was just wondering if I can get some tips on what to look for from the forum.

My exact mower did the same thing. The motor mounting bolts were not tight and the motor could move around.

 

[Peva]

Not all have the time to keep a manicured lawn. With that most mulch setups are terrible at cutting grass without clogging. The only dedicated mulch deck that been though my shop has been the JD Freedom deck.

But even normal decks on some models have discharge problem in heavy grass cutting [tall grass]. The worst I have seen have been on Gravely mowers. I have had shut the decks move to a cut area, raise the deck, cut off the deck, let the clippings drop, and then with the deck still raised re-engage it. It is a rinse and repeat as long you cutting heavy grass. Yet I can take a Super Z and knee high grass with minimum problems.

One key thing with mulching is to travel slower giving the decks time

Yes I agree you do have to learn how to use it. you need to mow slower.

to clear the clippings and always cut dry grass.

On the two comments about mowing slower when mulching, here's a tip:
Having two blades on the spindles allows faster travel speed without sacrificing cut and mulching quality.

I am a DIYer, so I don't have the depth of knowledge of you pros, but I know that all but the base model EGo mowers come with double ("cross cut") blades (I don't know if double blade kits can be retrofitted to the lower models). I do know that the Ryobi riders (tractor and zero-turn models) come without the double blades, but they do offer kits for retro'ing them all at reasonable prices - $40 for full set for both spindles on my 30" ZT - not sure about the Ryobi walk-behinds, but I'm guessing they have kits for those too).

ANYWAY - I highly recommend double blades for maintaining cut and mulching quality at higher travel speed (or if grass gets a little taller).

Also, the Ryobis have 3 blade speeds, so I always keep it in the highest speed, which is a key to best cut and mulching quality - with little effect on battery drain rate because additional spindle power draw is mostly offset by reducing cutting time of same area (and other efficiencies of higher blade speed).

 

[Bruce Mowbray]

I had the same issue, It turned out to be the new belt. After sitting for who knows how long, all curled up in its carboard sleeve with six tight bends, it was those bends and the fact that it hasn't been "settled in" on my mower, it caused a notable vibration. It took about 20 hours of mowing for it to finally go away. I also get the same (but not quite as noticeable) when I take the mower out of winter storage and start mowing in the spring.

 

[churchill]

I have the Gravely HD ZT48 with the mulch kit and have been using it for 6 years now. Like has been said, the cut quality is poor if the grass is too long (> 2x cut height) and/or wet. It will leave mohawk strips between the blade sections. I have to clean the underside of the mower deck at least 3 times a season for optimum mulching results. I love how it grinds up he fall leaves though. Yes, you have to mow slower and more often than standard blade mowers, but my mowing time is therapeutic for me. Keep your blades sharp (I do mine every spring) and balanced too. Mulching really helps the grass in the long run because you're replenishing organic matter that helps add nitrogen back to your root zone. I watch neighbors bag their clippings and haul them away or have the trash company take them. Seems they spend as much time dealing with the clippings as they do mowing. Then they buy a lot of nitrogen to put on to make it look nice.

 

[Davenj4f]

Hi folks, new guy on the block. I really enjoy forums for just about anything I own. Okay to the point, I just purchased a 2018 Gravley ZT34, with a 6000 series Kohler motor. It was somewhat abused, ( oil like mud, belts and blades never changed or sharpened or at least 6 years) after all that abuse the motor is still strong after tune up oil changed bad fuel removed. After cleanup and new blades and belts and a new mulching kit, I am getting a strong vibration from the mower deck, I check pullies and grease fittings, but can't tell where the vibration is coming from, I know there is more troubleshooting I can do but was just wondering if I can get some tips on what to look for from the forum.

Bet you a lot of money the blades are not balanced. New blades are never balanced by the makers. A friend of mine had the same issue with a brand new mower. I balanced the blades for him, and then it was smooth as silk.

 

[pat_from_indy]

Thanks so much for getting back. I am in the process of checking some of the above-mentioned points, some I have already eliminated. Have anyone installed the mulch kit that is offer thru the Gravley parts catalog ? I have and I also installed one on a Dixson mower and got the same vibrations.

No reason why a mulch kit would cause a vibration unless incorrectly installed or the mower has some issue.

Most likely causes of vibrations would be pulley / bearing issues or bent blades / deck. Observe what exactly is vibrating as best you can. Is it the whole deck or just under the deck? Is it while mowing or even when the blades are not engaged?

 

[will55912]

When you have a mulch kit that is properly designed and you know how to use it properly, they do a great job. Yes, you have to learn how to use it!! I’ve have the mulch kit on my 1996 Toro 16-38XL and have neighbors who actually ask to use it because of the way the lawn looks when finished. Only time I don’t like the cut is when I can’t cut dry or grass is too long.

Great point on making sure the grass is dry. I have some neighbors that mow early morning (Summer) when there is a heavy dew on the grass, or even during a very light shower. Then they wonder why the grass clumps up and have patches of dead grass. Duh!!

 

[guitarman4805]

No reason why a mulch kit would cause a vibration unless incorrectly installed or the mower has some issue.

Most likely causes of vibrations would be pulley / bearing issues or bent blades / deck. Observe what exactly is vibrating as best you can. Is it the whole deck or just under the deck? Is it while mowing or even when the blades are not engaged?

My exact mower did the same thing. The motor mounting bolts were not tight and the motor could move around.

These responses are right on; my experience with a Gravely MiniZoom 34 had a abnormal vibration a couple of times during my ownership. The motor bolts worked loose, making balance a problem and the a two blade deck demands balanced replacements and if you subbed blades, pull both blades and make sure they are balanced, centered and not bent even the slighest. You can release the tensioner and turn both blades manually and see any mis alignment and blade tips should be same height when they come around. The other incident I had was I hit a surface root and somehow bent one of the hangar pins enough to throw the balance out. I also had an acorn jump up and lodge firmly in the v pulley; and causing a real teaser to locate. It was only noticeable with an open inspection of all the belts and drives. hope this helps.