Need to know how to properly set the guide wheel heights on the mower deck and the blade height for proper mowing heights.

Turn off the mower completely and clean out beneath the deck with a mower-cleaning tool to remove any built-up grass deposits. As debris collects inside the deck, the blades can't move freely and you'll have unusual patterns or unevenness forming in your lawn as a result. The mower-cleaning tool scrapes this debris off and restores the deck to proper function.
Measure the height of the mower deck with a ruler when the mower is on flat ground. The deck should be an equal distance from the ground on all sides to ensure an even grass cut. Adjust the leveling bolts on both sides of the deck as needed to readjust the height until it's even. If the mower hits something like a rock or a large stick while mowing, it may knock the deck off balance.
Inspect the deck for any dents or warping. Use a rubber mallet to carefully straighten any dents in the deck if the deck is metal. Plastic decks generally need replacement if they crack or warp.
Remove the deck for a more thorough inspection or cleaning as needed. Remove the grass catcher and take off the pins or mounting bolts holding the deck in place. Lower it to the ground and pull it out from under the mower. Unhook the cutting blade from the underside of the deck with a wrench and set it aside.
Sand off any rust with sandpaper and use the mallet or a hammer to eliminate any remaining dents or warps.
Reinstall the deck once any corrosion or dents are fixed.
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if you are talking about before even moving, it could be grass and dirt caked inside of the deck. If you are talking about when you start mowing, it could be front to back height adjustment. owners manual has instructions for adjusting deck height.

first make sure left and right sides are same height. Next, adjust front and back heights per users manual. If still off, make sure you dont have a bent blade or bent or missing front or rear deck link.

There are a couple of causes for this. Is the blade height the same on the new mower? Higher blade height could cause a lot of the grass to be blown out from under the deck, and not into the catcher chute.

On the trailing edge of the mower blades is a small 'wing' for lack of a better term. There are two types of blades, mulching blades that have a lower 'wing', while catcher blades that have a slightly higher 'wing' but it makes a difference.

If the season has been hot lately, the grass may not be growing as fast, hence less clippings, and less dense grass could also cause this.

Hello,

I am guessing that this was posted in wrong category.

You mention that you have to keep pushing / letting go of the accelerator. Is the engine RPM changing, or is the tractor surging, when you do this? What happens if you keep a steady pressure on the pedal? Isn't the throttle control via a lever on the panel?

Your uneven blade height can be caused by a multitude of issues.
1) If the spindles were changed, the wrong spindle may have been used on one side or the other.
2) The wrong blade adapter has been used on one of the spindles.
3) Mower deck has been bent
4) Mower deck is binding. Try raising it all the way up, and lowering all the way down. See if the uneven cut changes at both levels (all up or all down).
5) Blade is bent on one side, though this would usually cause such a ruckus and vibration it would be quite noticeable.
6) Belt is slipping. Yes, sounds strange, but if blade speed changes significantly, then the position where the grass is actually cut changes because the grass can "lean over" more.
7) Using a mulching attachment in tall grass can cause 1 blade to clog, and the cut grass that is swirling bends over other grass that needs to be cut.
8) Mower deck support bracket has been bent
9) Mower deck wheel has a bad bearing, and doesn't support the deck at same height as other side.
10) Mower deck is cracked / bent at a support location
11) You have lost a retaining pin at a support bracket and the bracket is loose.
12) A spindle's bearings are worn out, and the spindle is "jumping" as it turns.

If the blades are directly beside each other where they blades will overlap, it is normal for a small amount of height difference to occur. But, most decks have off set blades, one slightly in front of the other.

you should be able to raise the deck all the way, and pull the tractor's front wheels up onto something (landscape timber?) to get more access, then measure blade height in relation to bottom of the deck. If different, then you are looking at wrong blade / adapter or a spindle issue. If the blades are the same height, then you are likely looking at a deck support issue / binding in linkage.

Are your blades upside down? Mower deck level?Proper air pressure all 4 tires?Correct blades for the diameter of cut? Deck bent? Deck hangers bent?

It sounds like your mowing deck is too close to the ground. Can you adjust the blade height with a lever? I have a Craftsman riding mower, my deck height is adjusted manually with the use of a locking level shifter, be sure yours is set to the proper minimum height and this will eliminate driving the blades into the turf.

You need to turn that knob to its highest point with the deck height lever to its highest setting. Now turn that knob counter clockwise a few turns and let the deck lever all the way down. That knob will stop the lever part way down. If it mowes to high rase that deck lever again and turn that knob counter clockwise some more and let that deck lever down again. Repete till you have the correct cutting height. If you were cutting to low turn the knob clockwise insted of counter clockwise in the instruction above. The knob only set the stop of the deck lever. Once set the deck lever lifts the deck up and holds it but when you let that lever down it returns to its mowing set height.

There should be a lever with notches on each wheel to raise the mowing deck higher or lower. Make sure each wheel is the same height.