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Is there a way to fix the problem of grass left uncut between the blades? It is particularly bad between the left and center blade. I removed the relatively new blades (installed about 2 months ago), and rotated them, L to C, C to R, R to L, and I get the same result...2 stripes of grass the entire length of my mowing, which means I have to mow over the same path a second time, but slightly moved to the side to make sure my blades cut the 2 stripes that are left between the 3 blades. The grass between the left and center blade is up to 12" wide, while the grass left between the center and right blades is about 2-4" wide. I have the ProMaster 260.

Is the grass not being cut at all on those strips, or is it being cut but not the same height as the outside blades.

I don't think your new blades are as long as the original blades.

When did this start occurring? All of a sudden or over time? Did you do any maintenance just before the problem showed up? Have you leveled the deck? If you are skipping that wide of a strip, I would be checking to see if all blades are turning at the same speed. Have you checked to see if your belt is worn, all spindles are turning freely, belt tension is correct, and all pulleys are in good condition.

It has done this since I purchased the mower about 15 years ago. I purchased it used with about 100 hours on it. I took it to a Gravely dealer and told them about the two stripes. I asked if a new mower would leave the stripes. The dealer said, "no". I left it with him and told him to do what needed to be done to make it cut like a new mower that doesn't leave the stripes. He had it for about a month waiting on a part. When I got it, he said it's like new. I asked him to come with me to the side of his business where the grass was tall, like I typically cut when mowing. I ran the mower through the tall grass and it left 2 stripes. The dealer told me he had done all he could do. It's been that way ever since, but the stripes have typically been no more than 2-4" wide in tall grass/weeds, but it cuts OK without too visible of lines when mowing in the nice zoysia grass around my house. Now when cutting weeds, the left cutting side stripe is about 12" wide. I've looked at the blades under the deck. There is a visible space between the blades...probably 3/4", I'll guess. See attached photo. I will put a new blade belt on it tomorrow to see if that helps. One more thing...it doesn't matter if I drive slow or fast. The 12" path of taller grass left between the left and center blades is still there.

I haven't checked all of these things lately. I'm mowing a pasture right now that isn't mine. When I finish it, I'll bring the mower home and check all of this. How do I check for blades turning at the same speed? I've thought of this, and wondered if maybe the taller grass/weed is making the left blade turn slower, as if the belt is slipping around the pulley. I'll install a new blade belt before I mow tomorrow. Right now, my mower is sitting in a field with a broken PTO belt. I just purchased a new PTO belt this morning and I have a new blade belt in my shed. I'll install both belts tomorrow when I go back to finish mowing the pasture.

A common problem when grass to is too tall. Grass is laying down as mow the blade are not creating enough suction to raise the grass back up as blades are passing over it.

If you have notched style changing to none notched hi lift blades might solve the problem.
Notched blade

None Notched blade. Larger air lifts

GrumpyCat said:

I don't think your new blades are as long as the original blades.

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I'll measure them tomorrow. I have a 60" mower, so I assume the blades should be around 20" each. I remember reading that the Cub Cadet Tank mower has overlapping blades and the pulleys and belts have teeth so that the blades are positioned at 90 degrees to each other when the belt is installed so the blades won't hit each other when turning. The teeth in the belt and pulleys prevent the belt from slipping as you don't want the blades to hit each other. The overlapping blades keep the striping from happening. Yep, I just found it online. The 60" mowing deck uses three 21" blades. That's 63" of blades for a 60" deck. Maybe Gravely should consider this design.

StarTech said:

A common problem when grass to is too tall. Grass is laying down as mow the blade are not creating enough suction to raise the grass back up as blades are passing over it.

If you have notched style changing to none notched hi lift blades might solve the problem.
Notched blade
View attachment 68731
None Notched blade. Larger air lifts
View attachment 68732

Click to expand...

I use non-notched hi-lift blades.

SGray said:

I'll measure them tomorrow. I have a 60" mower, so I assume the blades should be around 20" each. I remember reading that the Cub Cadet Tank mower has overlapping blades and the pulleys and belts have teeth so that the blades are positioned at 90 degrees to each other when the belt is installed so the blades won't hit each other when turning. The teeth in the belt and pulleys prevent the belt from slipping as you don't want the blades to hit each other. The overlapping blades keep the striping from happening. Yep, I just found it online. The 60" mowing deck uses three 21" blades. That's 63" of blades for a 60" deck. Maybe Gravely should consider this design.

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Wasn’t thinking your stripe was so wide.

Your center blade is in front of the side blades, the cut overlaps but the blades can never hit each other. An uncut stripe can be produced cutting during a tight turn,

Am agreeing with others your center blade is slipping on the belt, or pulley slipping on spindle.

L= 20.5”
W= 2.5”
Center Hole = 5/8”
Rotary Copperhead #6180

That is a giant swath of truly uncut grass, in a straight line no less. Maybe check to see if one of your blades (center) is mounted upside down by remote chance. I have an old non-tech Jacbsen 46" and I don't have this problem when I mow any grass

Previously mentioned , the mower is being ask to do a job it wasn't designed to do .

This pic of blade overlap is difficult to see , but if blade overlap is sufficient a straight line can't be drawn parallel to the tractor length when any 2 adjacent blades are at 90° to the tractor . That's he purpose of a 3 blade geometry .

Thanks for all the recommendations/advice. I have a new long blade belt for the center/left blades and I'll get it installed this morning to see if that helps with the uncut grass striping on the left side. I don't have a short blade belt for the right blade, so I'll get one ordered and replace it soon. I'll also measure my blades to make sure they are 20.5".

SGray said:

I'll measure them tomorrow. I have a 60" mower, so I assume the blades should be around 20" each. I remember reading that the Cub Cadet Tank mower has overlapping blades and the pulleys and belts have teeth so that the blades are positioned at 90 degrees to each other when the belt is installed so the blades won't hit each other when turning. The teeth in the belt and pulleys prevent the belt from slipping as you don't want the blades to hit each other. The overlapping blades keep the striping from happening. Yep, I just found it online. The 60" mowing deck uses three 21" blades. That's 63" of blades for a 60" deck. Maybe Gravely should consider this design.

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The total length of the blades is not necessarily equal to the the width of the cut because they are mounted in an offset angle from each other.
Make sure the blades are mounted in the proper directionnot upside down). This could affect the uplift of the blade.A solution may be to install 3 mulcher blades which are high lift and supposedly cut the grass 3 times before exiting.There is a certain type of grass developed by by the state highway department that I call Victory Grass,because it has a "V" shaped seed pod on a long stem that is hard to cut.It lies down at the slightest breeze,and ducks the blades.It must be mowed forward and backward to get it all.
What is the length of an original blade? Compare it to the ones you have.They may be shorter than the original.
Is there a mounting angle adjustment for your deck?The angle of the deck in relation to travel direction will affect the cutting width.If the left side is offset further back than the right aside,it will create a missed spot in the grass and also reduce total cut width.Check your actual cutting path width.

SGray said:

Thanks for all the recommendations/advice. I have a new long blade belt for the center/left blades and I'll get it installed this morning to see if that helps with the uncut grass striping on the left side. I don't have a short blade belt for the right blade, so I'll get one ordered and replace it soon. I'll also measure my blades to make sure they are 20.5".

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The 20.5” measurement is taken diagonally.

The width of the blade is also important
A common problem is people fit a 3" wide blade of the same length as the original 2" wide blade thinking the bigger blade will be stronger & last longer
But it is actually a tiny bit shorter because it is a diagonal length so you do not get enough overlap and this leaves an uncut line
So slip the deck off or get under the mower and turn the blades so they are in line with each other
The gap between the two blades should be no more than around 1/8"
To save metal modern decks are shorter front to back so there is less space for overlap without the blades hitting
Old 42" decks used to have blades from 21.5" to 21.75"
But now days they are either just 21" so need replacing almost every season or 21.25" tops

SGray said:

Thanks for all the recommendations/advice. I have a new long blade belt for the center/left blades and I'll get it installed this morning to see if that helps with the uncut grass striping on the left side. I don't have a short blade belt for the right blade, so I'll get one ordered and replace it soon. I'll also measure my blades to make sure they are 20.5".

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Add a spring to the springs (#3) to add tension to the left belt around the pulley because it is longer than the distance around the shorter side of the right pulley.These springs can get weak over time,and that will make the left side slip easier than the right side.This is why the factory installed multiple springs on the idler on the left side blade.
Do this before installing new belt,you may not need a new belt after all,just save it for later.
Take off one spring and take it to a hardware store for comparison.A same diameter,shorter spring will be good,as long at the wire of the spring is the same gauge diameter is the same.You should be able to tell the difference by pulling on them to compare.All new springs of the stronger type will be better.Stronger is better,up to a point.Excessively strong springs will shorten the idler bearing life.
After years of slipping,the left side pulley may be worn to the point where it is not gripping the belt properly.The pulley pulls on the SIDES of the belt,not the center.That is why the profile of the belt is tapered,like driving a wedge into a block of wood.
The belt should not go so deep that it hits the bottom of the pulley.The shiny side of the pulley should look to be the same width as all the other pulleys
If this is the case,which I suspect,change the pulley and the belt(after adding springs to idler).
Put a little paint or lipstick on the pulley shiny inside and compare to the right side pulley to see if the groove in the pulleys is the same width.

closecut said:

Add a spring to the springs (#3) to add tension to the left belt around the pulley because it is longer than the distance around the shorter side of the right pulley.These springs can get weak over time,and that will make the left side slip easier than the right side.This is why the factory installed multiple springs on the idler on the left side blade.
Do this before installing new belt,you may not need a new belt after all,just save it for later.
Take off one spring and take it to a hardware store for comparison.A same diameter,shorter spring will be good,as long at the wire of the spring is the same gauge diameter is the same.You should be able to tell the difference by pulling on them to compare.All new springs of the stronger type will be better.Stronger is better,up to a point.Excessively strong springs will shorten the idler bearing life.
After years of slipping,the left side pulley may be worn to the point where it is not gripping the belt properly.The pulley pulls on the SIDES of the belt,not the center.That is why the profile of the belt is tapered,like driving a wedge into a block of wood.
The belt should not go so deep that it hits the bottom of the pulley.The shiny side of the pulley should look to be the same width as all the other pulleys
If this is the case,which I suspect,change the pulley and the belt(after adding springs to idler).
Put a little paint or lipstick on the pulley shiny inside and compare to the right side pulley to see if the groove in the pulleys is the same width.

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The fact that the dealer had your mower a month, fixed nothing, and said it was the best he could do and gave up, is mind boggling.

I replaced the long belt for the left and center blades and it made no difference. The blades are 20.5" in length, measured diagonally. The long belt spring is supposed to be 13-13.25" in length. I have it stretched a bit more to 13.5" to add some tension to the belt on the sheaves. The 2 stripes are still there. I dropped it off with my local equipment rental company yesterday that also does maintenance on mowers, weed eaters, tractors, skid steers, etc. The mechanic there thinks the problem might be related to my broken anti-scalp wheels on the front of the deck. He's going to give my engine a tune-up, replaced the anti-scalp wheels, level the deck, etc., and we'll see if the problems persist or not. Thanks everyone for your ideas and suggestions.

What would the anti-scalp wheels have to do with it? Are those anti-scalp wheels adjusted to be in constant contact with the ground? If so, they shouldn’t be.

I’ll say it again, has anyone checked the spindle bearings and pulleys? If the blades are not turning properly, they will cause your problem. Bad bearings will slow down blade speed. As stated, anti-scalp wheels are just a mechanic who has no clue as where to look to solve the problem. I wouldn’t waste $$$ replacing them.

Maybe he doesn’t have enough zinc in his motor oil?
(Makes as much sense as anti-scalping wheels.)

I went back and looked at the OP’s photo.
Two things stood out for me. First is it’s a pasture type property. Using even a commercial zero turn, it’s going to need double cutting.
Second is the rather large swath of partially and uncut grass.
I would go straight to that center spindle and pulley. Is the spindle locked up? Make sure that center blade is mounted right side up.

One last thing. Set your deck completely flat or 1/8” higher in the rear. Make sure the your wide open throttle RPM is 3,600 without a load.

Rivets said:

When did this start occurring? All of a sudden or over time? Did you do any maintenance just before the problem showed up? Have you leveled the deck? If you are skipping that wide of a strip, I would be checking to see if all blades are turning at the same speed. Have you checked to see if your belt is worn, all spindles are turning freely, belt tension is correct, and all pulleys are in good condition.

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Are you sure you installed the cutting side of the blade in the correct direction?

I’m trying to understand how in the world you’ve just lived with this thing cutting like this for 15 years?

Tiger Small Engine said:

The fact that the dealer had your mower a month, fixed nothing, and said it was the best he could do and gave up, is mind boggling.

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Shouldnt have paid him and said this is the best i can do...

Sounds to me like the reason it was sold after 100 hrs was it’s a poorly designed deck.

Try mowing when the grass is no more than 4" high once you have determined that you have the correct blade length. The 'teeth' on the belts do not keep the belt in 'time'. Check Spindle nut tightness and blade tightness.
Do your blades have engagement cutouts in the centre of them? Remove the blades and check bottom of spindles to be sure there is a positive engagement.
I should have looked at the photo first! You are cutting a field with way too Tall grass for your mower. The front wheels are likely flattening it before the blades get a chance to cut it.

coffeesnob said:

Sounds to me like the reason it was sold after 100 hrs was it’s a poorly designed deck.

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I doubt that was the case. It can be made to cut better. However, a zero turn isn’t going to cut that stuff like a tractor pulled Bush Hog.

I agree with MParr, I was reading through this list of posts and most people are missing the obvious. A Gravely mower is a fantastic machine, but it's just one tool that is designed for a specific purpose. (Bush hogging aint it) For example, would you use a hammer to drill holes? You can make holes with a hammer, but it's usually not the right tool to make holes and usually not the right choice for that job. In this case you're mowing a pasture with all types of stemmy tall thick grasses and weeds. The tool that is best suited for that job is a tractor with a bush hog. You can mow it with the gravely, but you should be raising the deck up as high as possible on the first pass and make a second pass after you cut the bulk off it. I don't think there's anything wrong with your mower or the dealer that worked on it. You'd be doing yourself a favor by accepting that you're not using your equipment right and understand, you're way off in your expectations of what you think it can do.

I have the stripe issue as well … doing my head in

Scotty xd said:

I have the stripe issue as well … doing my head in View attachment 68809View attachment 68810

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IF you have sharpened the blades and Checked top and bottom of Spindles for nut and blade(s) tightness, Belts tight and in good condition, then check Blade length. If all of the above are ok then IDK. Try longer blades?

SGray said:

Is there a way to fix the problem of grass left uncut between the blades? It is particularly bad between the left and center blade. I removed the relatively new blades (installed about 2 months ago), and rotated them, L to C, C to R, R to L, and I get the same result...2 stripes of grass the entire length of my mowing, which means I have to mow over the same path a second time, but slightly moved to the side to make sure my blades cut the 2 stripes that are left between the 3 blades. The grass between the left and center blade is up to 12" wide, while the grass left between the center and right blades is about 2-4" wide. I have the ProMaster 260.

Click to expand...

It simply looks like the grass being so tall it's being pushed down by the tires, I know cutting with my Kubota B1750, regardless, if using the belly mower or the rear bushhog, it'll leave those very same marks in the picture.

SGray said:

I'll measure them tomorrow. I have a 60" mower, so I assume the blades should be around 20" each. I remember reading that the Cub Cadet Tank mower has overlapping blades and the pulleys and belts have teeth so that the blades are positioned at 90 degrees to each other when the belt is installed so the blades won't hit each other when turning. The teeth in the belt and pulleys prevent the belt from slipping as you don't want the blades to hit each other. The overlapping blades keep the striping from happening. Yep, I just found it online. The 60" mowing deck uses three 21" blades. That's 63" of blades for a 60" deck. Maybe Gravely should consider this design.

Click to expand...

That's not true. They overlap and the total cut is 60".

SGray said:

Is there a way to fix the problem of grass left uncut between the blades? It is particularly bad between the left and center blade. I removed the relatively new blades (installed about 2 months ago), and rotated them, L to C, C to R, R to L, and I get the same result...2 stripes of grass the entire length of my mowing, which means I have to mow over the same path a second time, but slightly moved to the side to make sure my blades cut the 2 stripes that are left between the 3 blades. The grass between the left and center blade is up to 12" wide, while the grass left between the center and right blades is about 2-4" wide. I have the ProMaster 260.

Click to expand...

I spent a considerable amount of time researching this after my zero-turn (Toro Timecutter) had the same issues with leaving grass uncut in the center of the mowed strip. I actually wrote a computer simulation of grass being cut with various blade configurations on mowers to better understand it. Here's what I learned; maybe it will better help you understand the problem.....

1-Multiblade System Issues: If you have a multi-blade system (2 blades or more), and the blades don't overlap (they aren't staggered from front to back) then it is most likely impossible for the bladed to cut all the grass in the center. The only way they could is if the bladed are 'synchronized' so that they can overlap the middle of the mower, but can never collide. You can easily check this by looking under the mower and turning the blades by hand. If they never over lap the middle line of the mower, then they will always leave some grass uncut in the center. Some design 'blow the grass over', increasing the odds of it being cut by the blades on either side, but it never works 100% on these designs.

2-Circular Blade Issues: Grass that enters the deck in the center of each blade is twice as likely to be cut as it can be cut by the front of the blade, then there's a chance it will be cut by the rear of that same blade just before it leaves the rear of the deck. Grass near the sides of each blade is statistically have as likely to be cut, although it's odd's are a bit better because the blade sides cover more area due to horizontal movement. In addition, because a blade is circular, once side of the blade (relative to the mover's left or ride) is moving slightly faster forward and the opposite side is moving slightly slower--both because their velocity is added/subtracted from the forward speed of the mower (assuming it is moving). So the (from above) counter-clockwise side of each blade is actually cutting slower, and is more likely to miss or fail to cut a blade of grass. Finally, the radial area that a blade covers is less the further the grass is from the center of rotation for the blade--therefore grass is far less likely to be cut the further it is from the center of each blade, which is why uncut strips usually seem to be on the left and right of each blade (and the center, which is actually the right side of the left blade and the left side of the right blade combined). Always run the blades at maximum speed. Slower rotation increase the odds of missed blades of grass. The only blade configuration that is 100% consistent across the cutting deck would be a 'horizontal blade', i.e. a "real mower" like the old-fashioned push mower with a 'rolling blade'.

3-Cutting Blade Factors: The faster a blade rotates, the more likely it will hit a blade of grass, not to mention the less likely the grass blade will be pushed over instead of cut: important with 'wire-like grass'. This is also why blade sharpness is important. If a cutting blade has large areas with 'dings' or dull spots in it, those areas will push over grass instead of cutting it.

4-Mower Speed Factors: This relates to several of the above items. The faster you mow (forward velocity of the mower) the more likely grass will be missed because of grass being close to the edges of the blades, blades not having time to 'stand up' after being pushed over by wheels, and various other things tied to items above. Everyone hates that you can't mow faster, but the truth of the matter is that the slower you travel on the mower, the less likely grass will be missed.

5-Check under your deck for 'clogs' of grass. I noticed that mine was missing more than normal, and it turned out there was a bunch or soggy grass caked on the sides and center of my deck, preventing the blade from cutting on the edges and center of the deck properly. Giving it a good scrubbing totally cleared out the problem. I now wash the underside of my deck with a custom tool ever cut.

Hope that helps--most important is to cut as slow as you can, with blades rotating as fast as they will go, with a sharp blade and a clean deck and know that every circular blade system has variations of the exact same issues (it's all just math!). It was a learning experience studying this and writing my simulator, but now when I mow I find myself visualizing exactly what's going on when I see a problem.

OP - please let us know how your solve the problem. I thought maybe the blade were out of sync - that is, not mounted correctly relative to each other. But that's a long and continuous stripe.

My brother tried cutting a spot he'd let get high with a Yardman/MTD. He was stalling and squalling belts. He quit and said have to get bush hog. I told him I'd cut it. He asked what with. I said my 30" Snapper, he laughed. I mowed it, he asked why it would do what his couldn't. I said in a feminine voice, yours is for clipping the lawn, switched to masculine, said mine's for cutting the grass. One long blade with high tip speed and one belt, two pulleys VS two, short, slow tip speed blades, buncha pulleys and long convoluted belt(s).
You're trying to bush hog too fast with a lawn clipper. That front blade isn't able to hold speed.

Take blades off and look at them.
Is cutting leading edge rounded towards the blade ends? That's how it usually goes. Then, it will cut less in that area.
Are blades perfectly straight or bent? If you have bent edge, it will cut differently. Last week I pulled my Toro blades off to sharpen and, or horror, one was bent to about 15 degrees up. Considering, what I mow, quite normal.

Has anyone mentioned the middle blade should be longer. I have a Snapper zero turn, cutting high weeds "dandelions" mostly, making the return cut darn near all the D's were still standing. Finally called factory, they said the mower deck needs to be 3/8" lower in the front. That fixed the problem.

Any closer and they will be slapping each other

Gord Baker said:

IF you have sharpened the blades and Checked top and bottom of Spindles for nut and blade(s) tightness, Belts tight and in good condition, then check Blade length. If all of the above are ok then IDK. Try longer blades?

Click to expand...

Scotty xd said:

View attachment 68812View attachment 68812
Any closer and they will be slapping each other

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I would suggest your losing lift with those blades. I can not prove that. Only thing I can say is check the front edge is lower then the back 3/8". Looks like the deck needs welding repair.

Something else to check is the deck itself What I am referring to is some decks will have a flat plate that protrudes under the front of the deck to help act as a guide to direct the discharged grass, but will lay taller thicker grass down and not allow the blades to pick it back up. And seems to effect the center blade more than others but is some cases will cause a skip between the blades on two deck systems.

Johner said:

Has anyone mentioned the middle blade should be longer. I have a Snapper zero turn, cutting high weeds "dandelions" mostly, making the return cut darn near all the D's were still standing. Finally called factory, they said the mower deck needs to be 3/8" lower in the front. That fixed the problem.

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That 3/8” higher in the rear doesn’t apply to all brands.
For the OP’s Gravely, all blades are to be 20.5” in length, 2.5”wide, 0.25” thick, and have a 5/8” center hole.

I've had a similar problem with my ZTX42 since new. The deck has no baffles, just plain open. Other decks with baffles don't seem to have this problem.

SGray said:

Is there a way to fix the problem of grass left uncut between the blades? It is particularly bad between the left and center blade. I removed the relatively new blades (installed about 2 months ago), and rotated them, L to C, C to R, R to L, and I get the same result...2 stripes of grass the entire length of my mowing, which means I have to mow over the same path a second time, but slightly moved to the side to make sure my blades cut the 2 stripes that are left between the 3 blades. The grass between the left and center blade is up to 12" wide, while the grass left between the center and right blades is about 2-4" wide. I have the ProMaster 260.

Click to expand...

My 472 does that whenever I mow too fast in tall grass. I’ve always had to just go real slow and/or mow it twice. It doesn’t leave streaks when cutting 4-6” tall grass, And, it cuts better at around 3” setting. Just remember, a zero-turn is a finishing mower, not a bush hog. It’s not designed to make clean cuts in very tall grass.

The grass you are cutting doesn't seem that tall but try it on shorter grass first. If the stripe is still there, it appears that the center blade is not cutting, i.e., the center blade is not turning. You did say you replaced 3 blades, right? Is the center spindle stuck? Make sure the blade is engaged with the spindle shaft. It is possible to bolt on the blade without the blade being engaged to shaft in which case the spindle turns, but not the blade due to the grass resistance. On all mowers the blades are offset so they overlap the cut.

Scotty xd said:

View attachment 68812View attachment 68812
Any closer and they will be slapping each other

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Keep in mind that they are not always in that position. If that’s how they are synchronized, the when they’re both 90 degrees to that they will miss spots in the center if you go too fast.

SGray said:

The dealer told me he had done all he could do.

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Try to find a more experienced tech that is independent of the brand.

I mean, he insinuated he fixed it, you showed him the problem still persists and he just shoved it off basically telling you he can't fix it when his story was different just moments before lol.

SGray said:

Is there a way to fix the problem of grass left uncut between the blades? It is particularly bad between the left and center blade. I removed the relatively new blades (installed about 2 months ago), and rotated them, L to C, C to R, R to L, and I get the same result...2 stripes of grass the entire length of my mowing, which means I have to mow over the same path a second time, but slightly moved to the side to make sure my blades cut the 2 stripes that are left between the 3 blades. The grass between the left and center blade is up to 12" wide, while the grass left between the center and right blades is about 2-4" wide. I have the ProMaster 2

Click to expand...

SGray said:

Is there a way to fix the problem of grass left uncut between the blades? It is particularly bad between the left and center blade. I removed the relatively new blades (installed about 2 months ago), and rotated them, L to C, C to R, R to L, and I get the same result...2 stripes of grass the entire length of my mowing, which means I have to mow over the same path a second time, but slightly moved to the side to make sure my blades cut the 2 stripes that are left between the 3 blades. The grass between the left and center blade is up to 12" wide, while the grass left between the center and right blades is about 2-4" wide. I have the ProMaster 260.

Click to expand...

Check that your spindles are good. Pull off your belt and check to make sure there's no bearing noise and they free spin. I had one that would get hot after I mowed a few rows and slowed down that blade. So I thought dull blade or loose belt or that the hole in my old deck wasn't letting it create the suction it needed to lift the grass or something. Pulled my hair out for a couple seasons making sure I cut the grass before it got more than an inch or two otherwise I had to go over a lot of it twice. Check your spindles .

Johner said:

I would suggest your losing lift with those blades. I can not prove that. Only thing I can say is check the front edge is lower then the back 3/8". Looks like the deck needs welding repair.

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It definitely doesn’t need welding. I can see how you can think it does but there is definitely no crack there. It’s practically a brand-new mower 60 hours.

Scotty xd said:

It definitely doesn’t need welding. I can see how you can think it does but there is definitely no crack there. It’s practically a brand-new mower 60 hours.

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Look at the photo that you put up. There definitely needs to be a bead put on where the two curved baffles meet.
Your other problem is those Gator style blades. They aren’t good for anything but fall leaves.

MParr said:

Look at the photo that you put up. There definitely needs to be a bead put on where the two curved baffles meet.
Your other problem is those Gator style blades. They aren’t good for anything but fall leaves.

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Nope doesn’t need welding here’s another picture different angle red arrow is from another story ….. these blades are better for mulching grass

Make sure your blades have been mounted correctly to run in the right rotation. I purchased a rider from a relatives widow that said her husband bought a new mower just before he passed away because the old mower no longer cut the grass well. Upon inspection, I discovered that one of the blades was installed upside down, which meant that the back side of that blade was striking the grass instead of the sharp side.I also discovered that the center star that fits into the blade hole was not all the way in and this caused the ends of the blades to be off in height to one another. One end of the blade was 1/2” higher than the other end.

SGray said:

Is there a way to fix the problem of grass left uncut between the blades? It is particularly bad between the left and center blade. I removed the relatively new blades (installed about 2 months ago), and rotated them, L to C, C to R, R to L, and I get the same result...2 stripes of grass the entire length of my mowing, which means I have to mow over the same path a second time, but slightly moved to the side to make sure my blades cut the 2 stripes that are left between the 3 blades. The grass between the left and center blade is up to 12" wide, while the grass left between the center and right blades is about 2-4" wide. I have the ProMaster 260.

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I have the same problem with my 2 blade Husqvara YTH22V42 where there is a strip about 3" wide that seems to correspond to the right (discharge side) blade spindle location or there abouts. I am using high lift non mulching blades and it always seems to do it whether the grass is short of taller. I thought high lift blades would fix the problem but they don't.

Looks as if 2 decks were welded together without the offset recommended in #13 so the blades will always hit each other .

Looks as if 2 decks were welded together without the offset recommended in #13 so the blades will always hit each other .

We are now getting 2 different people with problems. Should start a new thread.
To the OP: "When I got it, he said it's like new. I asked him to come with me to the side of his business where the grass was tall, like I typically cut when mowing. I ran the mower through the tall grass and it left 2 stripes"...
Do you ever just cut normal length grass? And if so, what does that look like?

Dwayne Oxford said:

My brother tried cutting a spot he'd let get high with a Yardman/MTD. He was stalling and squalling belts. He quit and said have to get bush hog. I told him I'd cut it. He asked what with. I said my 30" Snapper, he laughed. I mowed it, he asked why it would do what his couldn't. I said in a feminine voice, yours is for clipping the lawn, switched to masculine, said mine's for cutting the grass. One long blade with high tip speed and one belt, two pulleys VS two, short, slow tip speed blades, buncha pulleys and long convoluted belt(s).
You're trying to bush hog too fast with a lawn clipper. That front blade isn't able to hold speed.

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Blade tip speed is limited by ANSI to 19000 FPM, regardless of the blade length. Unless the MTD was set up wrong by the dealer (very possible, as the "dealer" for most of them are big box stores), the blade tip speed SHOULD be the same. I think the 30" blade acts more like a bush hog than the multi blade deck on the MTD, and that's why it works better. Plus, Snapper decks are generally regarded as better than MTD's, and probably flows better.

Just in case someone didn't understand blade overlap in the previous pic i did a little photo work to make things clearer .

Thank you for the picture. Was helpful in understanding problem. Maybe front blade dull?

SGray said:

I'll measure them tomorrow. I have a 60" mower, so I assume the blades should be around 20" each. I remember reading that the Cub Cadet Tank mower has overlapping blades and the pulleys and belts have teeth so that the blades are positioned at 90 degrees to each other when the belt is installed so the blades won't hit each other when turning. The teeth in the belt and pulleys prevent the belt from slipping as you don't want the blades to hit each other. The overlapping blades keep the striping from happening. Yep, I just found it online. The 60" mowing deck uses three 21" blades. That's 63" of blades for a 60" deck. Maybe Gravely should consider this design.

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In case you're unaware, the blades are measured diagonally. That's why you can have 63" on 60 " deck. Also, sloing down your mower speed can sometimes get rid of those stripes. The first thing I would check is belt tensioner(2)

Get an Exmark or a Bad Boy.

eyekue138 said:

Get an Exmark or a Bad Boy.

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You’ve got to be kidding.

Someone who was talking about the computer software and models etc, which is way overkill for this and I doubt it helped them solve their problem at all, was talking about the faster you spin the blade the better.
This is not actually true.

In the arena we're dealing with it probably is because we're probably not able to get a blade to spend consistently at too high of a speed in any type of grass but you can certainly lower your quality of cut by spinning a blade too fast!

There are a lot of other factors at play here and you're not going to determine them all with a computer model or program because you would need some very sophisticated scientific measuring devices and you would have to test repeatedly and test a multitude of decks to actually come up with a theory or consensus.

Back to the problem though, it seems that the first thing that comes to mind is that Center blade is certainly not spinning fast enough for much at all. I don't recall the original poster ever answering the question of making sure if that blade was on the correct direction..
I get a handful of hours every season in with the blades on upside down and the customers have no clue that they are not cutting properly!

If the blade is then I suspect the belt is slipping on the pulley. You should be able to check this fairly easily by engaging the blades and just sitting there not even mowing anything for a few seconds to maybe a minute and then turn it off and start to feel the other pulleys and see if the center pulley is noticeably warmer than the other ones.

You might have to run a couple of minutes for this but I have found this problem before.

I've also had several gravely and ariens machines where the belt tension was way off for several different reasons but the main answer was to put a new belt on it and a new spring or a shorter spring or relocate the spring mounting point on the deck.

All I know is if that Center blade was spinning faster and maintaining its torque and speed, it would be cutting better than that.

When cutting taller grass, weeds, raise the deck and cut then lower and recut. The front of the deck will flatten the grass and it may not have a chance to be sucked back up to be cut.

Freddie21 said:

When cutting taller grass, weeds, raise the deck and cut then lower and recut. The front of the deck will flatten the grass and it may not have a chance to be sucked back up to be cut.

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Freddie21 said:

When cutting taller grass, weeds, raise the deck and cut then lower and recut. The front of the deck will flatten the grass and it may not have a chance to be sucked back up to be cut.

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Do as Freddie21 suggested, and I’ll add:
If all
Other suggestions have been checked, then try mowing in the late afternoon or evening when the grass is dry. Even on a day without rain, the grass can be very damp in the morning from dew overnight.

Scotty xd said:

View attachment 68812View attachment 68812
Any closer and they will be slapping each other

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Those blades are way too far apart
When using Gators I often have to buy a longer set & grind then down to fit
You measure blade spacing cutting tip to cutting tip
And cutting tip to cutting tip those blades will be 1/2" apart
The end of the blades often has to rake backwards from the tip to the flute
The blades are too short .

SGray said:

Is there a way to fix the problem of grass left uncut between the blades? It is particularly bad between the left and center blade. I removed the relatively new blades (installed about 2 months ago), and rotated them, L to C, C to R, R to L, and I get the same result...2 stripes of grass the entire length of my mowing, which means I have to mow over the same path a second time, but slightly moved to the side to make sure my blades cut the 2 stripes that are left between the 3 blades. The grass between the left and center blade is up to 12" wide, while the grass left between the center and right blades is about 2-4" wide. I have the ProMaster 260.

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Did you ever get the problem fixed?

Coincidentally I always get a strip of poorly cut grass at about the right side of the left blade/center blade overlap. John Deere 62" deck. Blades factory new measure 20 9/16" long. I replaced my blades, then looked at the upper side of the deck and the idler pulley was tilted! The lower bushing was almost worn in half. $75 for new bushings and pulley and a new belt later, all seemed OK until I cut any grass and found the blades were turning slowly - found that in replacing the belt it slipped over the engine pulley. Got that sorted, and it cut very well - this is the second time I have had to replace that pulley though in maybe 450 hours. JD dealer said the three pulleys need to be replaced every year or so, but the other two are un replaced and work fine. The idler pulley is the only one with a grease zerk (which I use religiously) so you would think it would wear slowest, not fastest.
BUT...yard got cut - this time of year my grass grows an inch a day so going a full week between cuttings is not possible.

Scotty xd said:

View attachment 68812View attachment 68812
Any closer and they will be slapping each other

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The blades look like they are to high in the deck, are your blades straight or bent/offset like the factory blades?