F3680 mower deck height adjustment

jcummins · May 27, 2015

My first mowing with this F3680, I'd say the cut is excellent. Better than I hoped for. Perhaps it looks so good because it is shorter than I normally cut and that may be a more groomed look. But I want to raise the cutting deck height.

Over the years my understanding is that the front of the deck should be slightly lower than the rear. Supposedly that gives a better cut, with the deck slightly angled into the grass. The gauge wheels are set in the 3" position, the rear lift rods are set in the 2.75" position. The exact opposite of what I thought I knew. Now, I'm scratching my head, do I raise both equally or do I adjust it so the front is lower by 1/4". Given the cut quality, I'm now lost.

jcummins · May 27, 2015

I have a F3680 manual, but I do not have one on the mower deck. I've got good info on it though from the F3680 WSM manual you can download. I may have figured this out.

On the lift rods there are washers, 6 of them on my mower deck. Although I cannot find the source, I recall the washers are for fine tune of the deck height, left to right, etc. They've got 3 of the washers below the adjustment collar...and that adds to the rear deck height. And 3 washers measure 1/4". Not sure why the height adjustment was done in this way, but as long as I understand it, it's fine.

EastTexFrank · May 28, 2015

It took me a little while to figure it out also. It's a good, robust system but not at all intuitive. There are probably a dozen deck height adjustment systems out there that are a lot easier to use. Once I got mine set to where I wanted it, I haven't messed with it since.

jcummins · May 28, 2015

Yes I agree. The ZD326 I had was the twist of a knob, however, I had to go through some troublesome adjustments to get the deck level. 5 years later, it needed that same adjustment again. The F3680 deck looks complicated, at first look, but actually it's fairly simple, once you understand the different settings. And as you said...robust. You can see it, compared to others. Once I set it, probably won't touch it again.

johncar · May 29, 2015

Hi jcummins, I have a copy of the deck manual and you can download it from the Kubota support website:
http://www.kubota.com.au/media/2287/ops-rotary-mower-rck72r-60r-f36-rck54-f28-k5682-7111-8.pdf

You are probably aware of all or most of this by now but just though I would share my journey of discovery so far:
The recommendation is to make the deck level so what ever you set the front wheels to you do the same settings for the rear deck supports. I set mine at B-Y from memory which is the second most highest setting and that is because I am mowing my paddocks which are a bit rough in places with plenty of rock and debris which I want to keep the blades out of. My place is also quite hilly with areas 25 to 30 degrees so I hope the mower is up to it.
The washer shims at the rear supports are to fine tune that height and to get mine dead level I ended up with five on top and one left under and I assume that is due to the rubber block being a bit worn and compressed to some degree from new perhaps.

The thing to be aware of when making the adjustments is that the rear supports are numbered and lettered in the opposite direction to the front ones so where A is the top hole on the front pin and X the top hole in the collar, on the back ones, A is the bottom hole on the pin and X is the bottom hole on its collar. So using the same relative holes in the opposite direction should give you roughly level.

I have noticed too that when mowing that the two front wheels on the deck stay well planted on the ground when the deck control lever is in the fully forward position allowing the deck to properly float on the front jockey wheels but if the lever is in the neutral position one corner of the deck will lift seemingly not allowing the deck to float properly. I was initially mowing with it in the neutral position which was probably not the best idea.

jcummins · May 29, 2015

Thanks for the manual link.

Keep us posted on your experience on slopes...I have the same issues.

So far the F does crabs a little, nothing even close to the ZD, .... just noticeable. I had 275lbs on the rear of the machine, not sure why the extra weight since many F's have no weights, and I've removed to see what difference it makes. Will mow again first of the week.

Researching different tires...but not have much luck. Both local Kubota dealers have not been much help. But besides the muddy areas around the pond, kind of thinking holding the hillsides would be better with better tires.

Rip · Jun 15, 2015

I also found the deck height adjustments to be more fiddly than it could be, but is pretty simple. As my machine had seen about 1500 hrs in council use I discovered early on that the shafts of the rear deck links had worn nearly all the way through but caught them in time and welded them solid losing just the bottom hole. Although I also run my deck at around 4" (10 cm), once I had it at a reasonable level I figure on just leaving it there.

As I am pushing the envelope on this (or any) machine on the steep 1/3 of our property I did add 3" (150 mm) wheel spacers to widen the main wheel track by 6" and also liquid-filled (water w/some antifreeze for anti-corrosion) those tires which added about 150 lb total and further helped the already good traction (new turf tires) and stability.

My machine was already equipped with the stock 110 lb rear counter weight but I figured I could use some more to take better advantage of the rear drive axle especially when I was partially lifting the mower deck to maximize main-wheel traction on the steeper hills (35+ deg), so I had another 115 lb (52 kg) weight fabricated out of steel and bolted it on top of the existing one. It helped noticeably. I had heard that the newer machines with the extra-wide wing-decks use about this much counterweight.

I was also looking to add a 2" trailer hitch receiver but figured to heavy-up the counterweight bracket before loading it any more..... however, if I decide to do a hitch-ball type, I may just sandwich a flat plate between my weights and let it go at that.

J Cummings - Your crabbing situation could be due to worn rear-axle bushings/bearing perhaps due to steering ram over-travel.....should check that possibility as JohnCar found.

Cheers, Rip

johncar · Jun 15, 2015

Some great info there thanks Rip,

Interested to hear you are working on such steep slopes with it as 35 Degrees is getting up there. I couldn't find any other tyre choice through Kubota so rather than risk too much out of sync with the tyre diameters I will probably just fit a new set of turf tyres too when I can find a bit of spare cash. I do tend to slide down the slopes a bit when travelling across them but our climate is fairly dry and the grass can be a little slippery so there may be not much I can do about that.

Where did you source the wheel spacers? if you don't mind telling me as they sound like something I could use too and plenty of my block is 25 - 30 degrees plus. The mower feels fairly stable but an extra bit of track is very appealing.

For now I have fixed my steering ram over travel by turning up a nylon spacer and fitted externally on the ram as per the pic below. I was able to adjust the front tie rod end in enough to limit the right hand lock and then the spacer at 48mm long limits the left hand lock. I imagine that the kubot fix kit for this would be an internal spacer to do the same job but I didn't feel like pulling the ram apart so it seems so far so good with what I did. I machined in a bit of a recess so that debris is less likely to get jammed between the spacer and the push rod seal.

Rip · Jun 16, 2015

Hi John, I got the wheel spacers from Christian Hansen at thetrackscompany.com Phone +1-510 601-7550 in California. They were under US$300 including shipping two years ago......they fit perfectly and looked quite well made. There are a couple other outfits that make other styles but you seem to have a pretty well equipped shop so could fabricate something.

Your solution to the steering ram issue may well work long-term....I will have to see if I have the same issue.

The tyres on the machine when I looked at it were completely worn out (as were the mower blades) and I got the dealer to include new ones, but he was not going to go more than OEM....at least they were brand new.....more aggressive would be better traction, but at least I do not tear up the grass when I do spin a bit......but all we have is "mowed paddock" and not lawn.....works for us! The whole 4+ acres was quite overgrown (belly high to a horse) when we got it back in 2012 (renters, you know) so I put the F through a torture test for the first few months.....it did it (and on just a single V-belt, not the twin it should have had).

Cheers, Rip

jcummins · Jun 16, 2015

Rip said:
I also found the deck height adjustments to be more fiddly than it could be, but is pretty simple. As my machine had seen about 1500 hrs in council use I discovered early on that the shafts of the rear deck links had worn nearly all the way through but caught them in time and welded them solid losing just the bottom hole. Although I also run my deck at around 4" (10 cm), once I had it at a reasonable level I figure on just leaving it there.

As I am pushing the envelope on this (or any) machine on the steep 1/3 of our property I did add 3" (150 mm) wheel spacers to widen the main wheel track by 6" and also liquid-filled (water w/some antifreeze for anti-corrosion) those tires which added about 150 lb total and further helped the already good traction (new turf tires) and stability.

My machine was already equipped with the stock 110 lb rear counter weight but I figured I could use some more to take better advantage of the rear drive axle especially when I was partially lifting the mower deck to maximize main-wheel traction on the steeper hills (35+ deg), so I had another 115 lb (52 kg) weight fabricated out of steel and bolted it on top of the existing one. It helped noticeably. I had heard that the newer machines with the extra-wide wing-decks use about this much counterweight.

I was also looking to add a 2" trailer hitch receiver but figured to heavy-up the counterweight bracket before loading it any more..... however, if I decide to do a hitch-ball type, I may just sandwich a flat plate between my weights and let it go at that.

J Cummings - Your crabbing situation could be due to worn rear-axle bushings/bearing perhaps due to steering ram over-travel.....should check that possibility as JohnCar found.

Cheers, Rip

My experience with the weight on the back is different. Had 275lbs, took it all off, and I could not detect a difference. It makes since to have some weight back there....but my judgement is still out on this. I've got some steeper sidehilling I'll be testing it with...to darn wet right now.

Yep, going to check that steering ram.

Got to get the money first, but fairly certain I will be replacing the turf tires with Carisle AT101, and perhaps put rimgaurd in them too.