OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Diplomat 430 Front roller assembly wear

I pulled apart my SB430 so I can get the reel,bedknife sharpened. I pulled apart the front roller assembly and it has pretty bad wear. Could have caused the alignment problems i have been having. The rear roller has no adjustment. Thought I would post some pic's so poeple can get an understanding how its setup..





Hasnt got the fine adjustment screws like Model 45's. As you can see its harder to adjust the reel, bedknife.

Hi Jason, thanks for posting the pics, it gives us a clearer picture of what is happening in the front end of a Diplomat....I think that you might have found the cause of the misalignment....not just the end caps (as I suspected) but in the assembly itself..
I now know the reason that a lot of dealer workshops don't like doing the reel/bedknife adjustments....there is no fine tuning....In my opinion, Scott Bonnar really lost the plot with this method.

I don't think reel adjustment needs to be difficult, Deejay. You can just put a piece of 0.002" brass shim in between reel and bedknife at each end, press the reel against the bedknife, and tighten the screws. Then rotate the reel to remove the shims. You will probably ruin the pieces of brass shim each time but it wouldn't hurt the steel reel and bedknife, and the pieces of shim can be quite small - perhaps 1 cm square. This is very similar to the procedure for adjusting the clearance between coil and flywheel.

That seems easy grumpy, but you would have to agree that the bearings would have to be in perfect condition, and the reel perfectly square to the bedknife which in itself would have to be true and aligned correctly to achieve the desired result....plus you can't work from the front on a Diplomat as you can on a SB45....because of the rear grass throw design...

Thanks for the replys..
What I didnt really mention properly is when I lift the front of the mower up the roller was all sloppy and loose. Like that spring is no good. The SB45 I had done it too.

Thanks for that idea grumpy I will try that! I'm getting the blades done so I will soon find out how hard it is to align. Just read a "toro university basics to reel mowers" PDF file off google. I enjoyed reading it very interesting!
I just bought an outboard motor so I told the missus Ill just sell the SB430 to cover the costs. It backfired! I sold it for $540 then the buyer changed their mind for obvious reasons so I just sold the SB45 instead for $500. I'm still in front so far the SB430 only cost me $20 where the SB45 owed me $500..

Heres anather error with SB430..


It really becomes a problem when you mow long grass if you keep the lawn short its ok. Its worn though the housing I cant weld cause its diecast so epoxy might be the go.
Lets keep these SB430's alive

Deejay, I think you only need the two reel bearings to both be in the same condition rather than perfect condition, and you have to be consistent between the two as to whether you push them down or lift them up to take up the clearance. If they are a bit worn, you might use a thicker shim than 0.002" (or better still, replace the bearings), to make sure the reel does not contact the bedknife. Obviously you also have to check that the bedknife is square to the frame, with the usual alignment tool, to get even cutting depth across the mower. Since you adjust clearance by moving the bedknife, if you find the knife is out of square to the mower frame when it has even clearance to the reel, you have to move one side of the reel with the slotted adjustment on one of the reel bearings, but that should be a once-and-for all alignment adjustment until the next time you have the reel ground. I think by the second or third time you did it the process would not be much harder than adjusting an SB45, but I agree you would not get quite such a precise adjustment by using a shim as you can get by feel. However, remember that John Deere recommends the shim method for their greens mowers.

Jason are you sure that roller-end is zinc, not aluminium? From the look of it it could be either. Epoxy will work on either one, but there should be a more permanent solution.

I will throw my 2 pence worth in even although it's been a couple of years since I adjusted my machine.

The soleplate is not adjustable other than on a pivot, so if it's not aligned with the frame, the bottom plate needs reground.

The cutter is fixed at one end and adjustable at the other.

Lets assume the bottom plate and cutter are perfectly ground.

You loosen back the 2 lock bolts and 2 swivel bolts on the soleplate and swivel it into within 0.002" of the left hand side of the cutter (pulley side)

When done tighten the 4 bolts.

You then loosen the 2 bolts on the non pulley side of the cutter and adjust the cutter to within 0.002" of that side of the bottom plate.

Tighten the 2 bolts and check.

In practice it's quite easy

The OP has movement in the spring of the adjuster, I dont think that is a problem because you have no weight on it, once it's on the ground their will be no movement.

Any movement at the front end is probably coming from elongated holes in the front roller arm assembly where the roller shaft goes through.

Grumby, From what I can gather it looks like the rear roller end is diecast. I've tryed welding diecast before it just burns up. It's like the two piece clutch diecast thing ( the one that stops the blades) that the SB45 has. They crack and all you can do is replace it.

Thanks kempe I'll do that, surely it can't be that hard. You make it sound easy enough. A question about yours, when you squeeze the clutch handle does it just stop or does it roll for bit first? Im thinking it might be the rear roller alloy housing bottoming out.

When people say "diecast" they usually mean diecast zinc, but the two metals most commonly cast in a permanent mould (i.e. die) are zinc and aluminium. (For some mysterious reason Americans call zinc "potmetal".) The two metals look rather similar, but act differently. Zinc can't be welded, but can be soldered, with special solder and flux. Aluminium can be welded, with argon-arc equipment (Americans use helium instead of argon), and in a limited fashion can be soldered with a really special solder covered with an even more special flux. I think your roller-ends are probably aluminium, but can't tell from the picture. So, it may be that filling the hole with body-filler is the most practical solution available to you, unless you know someone with the right welding gear.

Looking at the wear on the outer edge of the rear roller I'm wondering if you have failed bearings?
Bit unusual for rear roller bearings to go because they only turn slowly it's the other 4 bearings that go first because they turn at engine speed.
When I replaced mine I used about 50% less fuel, that's how bad they were.:-)

Not sure about the housing bottoming out, is your grass thatched? maybe it needs scarified.

When I press the clutch handle she goes forward but I have overhauled the clutch, new lining and ring gear

Have you got drive or is it slipping, not sure from your post

Hi all,
Just an update on my diplomat. I have had in pieces ove winter. I decided to put it back together I replaced the roller and reel bearings. And had the reel,bedknife sharpened. A bit of fiddly work getting adjusted I closed the gap on the bedknife to the reel with a strip of newspaper. The reel has fine adjustment on one side so once I got that right it will cut paper and the the reel still doesn't rub on the bedknife.
I didn't do anything to the front roller assembly and its still leaving lines so might try replacingspring in front in the assembly to help firm it all up. The front jumps up and down on the bumps I try to slow the revs down but these damn diplomats go a bit fast I think. Motor doesn't like going slow either..

It's like I need to regroove the rear roller as it slips a bit on hills, you can see the wear on the previous photos. Anyone else tryed regrooving the roller? Most poeple would replace the roller I would think..

As a Scotty owner myself, I have never heard of anyone having to re-groove a rear roller. In fact, the Scotty Model 17 Supercut I have, has no grooves in the rear roller at all.
No greens mower I know of, have grooves; so the problem may lay elsewhere.
What sort of slope (hills) are you trying to mow, and is the grass wet whilst you're mowing? All cylinder slip a little on wet grass, but the weight of the machine usually overcomes this difficulty. You could also try mowing across the slope, rather than trying to mow up it.

Yeah it's on a slope I try to go down on the really steep spots if I try to go across it slides sideways. The lawn isnt wet at all either. The diplomat seems to drive a lot faster then my models 45's I've had before. I'll have to work with it then. I'll see how it goes after I put a new spring in the front roller assembly.
Cheers :-)

I replaced the front roller spring, I didn't realise that when I started mowing the height adjustment was slowly coming loose so the lawn got a nasty crew cut. But its come good now I just fitted a longer spring.
I fitted a new belt now it likes to drive itself when handle lever isn't engaged. Enough to be annoying going down slopes.
I can't really put much time into it now got heaps of uniwork, its mowing well so that's what really matters..

My machine started leaving lines when I mowed, also had the problem of the rear roller spinning on a slight hill I have.

Being spring time I have just spent 2 days of my holiday scarifying my lawn back down to almost soil level, no more lines and no more roller spin.
I would consider dethatching your lawn

Hi Kempe, that is good advice....Just a tip, after de-thatching, you may consider coring the lawn then applying a good quality fertiliser (Pivot 400 is very good) and then watering in well....The lawn will come up a treat!

Yeah, I also hired a corer and by god are they hard to manouvre!! (getting a bit old for this)
I also like to spray the lawn with wetta soil before watering, I buy the 1 litre concentrated and put half in the container that you connect a hose to and fill it up with water, makes the water penetrate the soil deeper.
Have also heard a cheaper way is to just use dishwashing liquid instead of wetta soil as it's the "sufactant" part that is important.
I wouldnt have called my lawn heavily thatched but 2/3 filled a 4 cubic metre waste bin and boy are they expensive to hire ($240)
All up this would have cost me over $400, hiring a waste bin, scarifyer, corer and trailer to transport it all, best to organise a whole property clean up at the same time, or share with neighbours
Will try to post a pic later on
PS Should add I also hired a rotary lawn mower for the heavy work of picking up after the scarifying as I didnt want to use the Diplomat for such heavy work. :-)

Hi Kempe, thanks for the reply mate, this is good advice and great for the archives. Looking forwards to the pics!

Lawn scarified and cored 2 days ago, currently being fertilized with high nitrogen for growth and watered well in after being sprayed with Wetta soil.
The small rise you see on the bottom pic, left hand side, was enough to spin the rollers when it was thatched