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Doesn't cut all the tall grass

#1

J

jk3700

I have a RZT-50 Zero Turn.

When I cut taller grass, the deck leaves a strip of uncut grass about a foot from the left side of the deck.

The uncut grass is about 4" in width.

Anyone have any idea why this is happening?

My blades are brand new.

My blades are not bent.

Just replaced the belt.

I do run a power bagger behind the mower and pickup grass as I go.


#2

M

mechanic mark

are your blades perpendicular to each other, 3 blade setup? are you blades OEM Cub Cadet blades?


#3

D

Darryl G

That's not uncommon when cutting tall grass. Does the strip fall in line with the left front caster wheel? It's probably laying the grass down as it rolls over and the grass doesn't stand up enough to get cut properly.

Same question as above - what blades are you using? I'd recommend high lift blades for those conditions. Also is your deck pitched properly? Do you keep your deck clean underneath? Are you going too fast and causing the engine rpms to drop? That's pretty easy to do when running a powered bagger in tall grass. Are your rpms up to spec to begin with?


#4

J

jk3700

mechanic mark said:
are your blades perpendicular to each other, 3 blade setup? are you blades OEM Cub Cadet blades?
Click to expand...

I do have the 3 blade setup. Didn't think the blade position was critical as they do not overlap.

Can you tell me why this would be critical?

I do not have cub OEM blades.

Can you tell me why the OEM blades would make a difference?


#5

J

jk3700

Darryl G said:
That's not uncommon when cutting tall grass. Does the strip fall in line with the left front caster wheel? It's probably laying the grass down as it rolls over and the grass doesn't stand up enough to get cut properly.

Same question as above - what blades are you using? I'd recommend high lift blades for those conditions. Also is your deck pitched properly? Do you keep your deck clean underneath? Are you going too fast and causing the engine rpms to drop? That's pretty easy to do when running a powered bagger in tall grass. Are your rpms up to spec to begin with?
Click to expand...

I do have high lift blades.

I'll need to check that front wheel laying the grass down.

Engine running at full throttle.

There is no drop in rpms as far as I can tell.

Can you tell me how the deck pitch would have an effect on the grass cutting?


#6

7394

7394

The blades do overlap, but in different locations, since blades are staggered with center being farthest forward on 3 blade.

So there is an imaginary line where overlap occurs. They just can never hit each other.


#7

B

bertsmobile1

When grass gets really tall quite a few things are working against you.
Firstly as already mentioned, the grass gets laid down flat and if long enough does not stand up again till the cutting section of the blade has passed so the blade just lays it down again.
Then their is the draught created by the blades.
It is strongest on the discharge side and weakest on the left side.
Also the higher the deck the weaker the draught.
Then there is the circulating mass of the cut grass itself that can push the uncut grass flat.
Three ways to overcome it.
1) heel the deck so the back is a lot lower than the front.
When you do this the blades cut better but all 3 cut at quite a different height so you end up with a wave type of level.
If this is only being done to cut catch up on really tall lawn it won;t matter because you can relevel the deck latter on

2) mow a lot slower

3) mow backwards


#8

D

Darryl G

jk3700 said:
I do have high lift blades.

I'll need to check that front wheel laying the grass down.

Engine running at full throttle.

There is no drop in rpms as far as I can tell.

Can you tell me how the deck pitch would have an effect on the grass cutting?
Click to expand...

The deck pitch effects the approach angle of the blades to the grass and how the grass moves into/around/out of the deck.

I just double cut tall grass to both cut any missed blades of grass and to disperse the clippings better. The 2nd pass can be done at speed and you'll get the best results going in a different direction, but I'll often go in the same direction to enhance the stripes.


#9

J

jk3700

7394 said:
The blades do overlap, but in different locations, since blades are staggered with center being farthest forward on 3 blade.

So there is an imaginary line where overlap occurs. They just can never hit each other.
Click to expand...

The blades are on a pulley that can slip. So I assume they could not hit because of their position.

I guess they could be mounted with the middle blade being higher or lower that the end blades.

I'll have to look at that.


#10

J

jk3700

bertsmobile1 said:
When grass gets really tall quite a few things are working against you.
Firstly as already mentioned, the grass gets laid down flat and if long enough does not stand up again till the cutting section of the blade has passed so the blade just lays it down again.
Then their is the draught created by the blades.
It is strongest on the discharge side and weakest on the left side.
Also the higher the deck the weaker the draught.
Then there is the circulating mass of the cut grass itself that can push the uncut grass flat.
Three ways to overcome it.
1) heel the deck so the back is a lot lower than the front.
When you do this the blades cut better but all 3 cut at quite a different height so you end up with a wave type of level.
If this is only being done to cut catch up on really tall lawn it won;t matter because you can relevel the deck latter on

2) mow a lot slower

3) mow backwards
Click to expand...

I have noticed in the past that if I cut at a lower height setting that there is less grass missed across the deck.

I am just puzzled by the fact that any grass could be missed by the blades under the deck.

I do slow to a crawl in higher grass to let the cut grass be sucked up into the power blower hose.

If I cut too fast, the cut grass packs in the discharge pickup and then eventually plugs up.


#11

B

bertsmobile1

The deck & blades are designed to cut a maximum of 4" off the top of the grass.
So anything taller than 8" is beyond the design capacity of the mower & deck.
cutting a trail through the savanah is what things like Brush Hogs are designed to do.


#12

D

Darryl G

As far as less grass being missed cutting shorter, that's because the lower the deck is, the higher the suction lift is. My mowers start loosing suction over 3.75 inches or so, but it depends on the lawn. I can cut higher on dense turf with good results whereas on scraggly turf there would be missed blades sticking up all over.


#13

D

ditto3000e

I have a different mower, but concept should be the same. Tall grass wont cut right unless you raise the deck to a certain height. Change direction and re-cut the lawn again for a nice smooth look. Or just run it over and leave it looking like a pile. Other reasons could be clogging, low tire pressure on a side or uneven deck. Wet grass has an effect as well as if your bagging or mulching. Blade is new so that should be passed.


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