OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Scott Bonnar 45 - Clutch Restoration

Hello. I'm new to this forum and to owning a reel mower. I purchased the mower from an older person who was getting rid of it. Got it for a good price. After doing some research on this site i see that the mower has had an engine upgrade to a Honda. The mower runs and starts okay. But I cannot get the blades to dis engage. I move the handle and it makes a clunking noise and keeps spinning. I've used it in the on position and it seems to work fine. Just wondering if in actual fact I'm doing more harm then good.
Also what's the best way to sharpen the blades. I've also read that you backlap the blades. Where do you purchase the compound that you use.
Any help would be much appreciated as the weather is getting better I'm looking forward to getting a nice lawn.
Images of my mower are below hop that helps.
Cheers
Brendan

Hello Brendansarah15,

From my observation it seems that the whole clutch body might be sliding back and forth on the engines PTO shaft as the engine side of the clutch half seems to be missing it's set screws that pin the clutch to the shaft and stop it from moving.
The clutch half you have on this mower has been replaced with the later upgraded version that utilizes two set screws that pin the body to the shaft at right angles.

Can you please physically grab the whole body and see if you can feel movement in it and then get back to us and we'll advise on what is required to be done.

Also on the side of blades, can you please tip the mower backwards and take some good close ups of the reel and where the blades come in contact with the bottom bed knife. I'll then be able to best advise you once I've seen those shots.

Cheers,
BB

Thanks for the reply. Yes I think you may be right with the clutch upgrade. And yes it does have the 2 grub screws on the shaft. The clutch seems to be very stable on the shaft and will not slide along it. I also tightened them to make sure. Do I need to adjust the arm that engages the clutch.

I've also attached some pics of the bottom plate and reel.

Hi Brendansarah15,

Firstly I'm sorry but I couldn't see the actual grub screws in the photos of the clutch and as such I thought they might be missing, but that's not the case here.
Now looking at your initial photos again it seems that there is a engine, clutch and shaft alignment problem.

Can you tell me that when you pull the starter rope does the clutch rotate totally in line (concentric) or is there some wobble associated during the rotation ?

Now as far as your sharpening is concerned it appears that your bed knife is no longer serviceable (going by your photo) as it's not straight on the engine side of the mower.
The basic fundamentals of a cylinder mower are that the blades on the reel must all be equally gapped all along your bed knife. In your case no amount of back lapping or sharpening will solve this. You need to have this bed knife removed and replaced by an engineer and only then can both the reel and bottom blade be sharpened and re installed correctly into the mower to obtain the correct mechanical alignment.

Cheers,
BB

Thanks again for the information.
On start up with the clutch in the off position. The clutch doesn't actually start moving for a few seconds then make a noise and started spinning from the pressure I assume, so I usually just turn the clutch to on. Could it be something to do with the arm that move to engage and disengage the blades
To remove the bednife isn't it just undoing the 6 screws in the bottom of the mower as I see you an just purchase the bednife blade separately.
Cheers
Brendan

Hi Brendan,

Sorry but I feel you may be misunderstanding the terminology. The Clutch body is the major circular part that we can see, the part that moves in and out is the clutch cone.

Now what I was asking is when you pull the starter the outer body should rotate while the cone should be standing still and this is with the lever in the leaning over position. Now while you are pulling the starter slowly is the body rotating absolutely straight or is there a bit of left and right wobble happening. Once you've given me the answer to that I can continue your assessment and we'll get to the bottom of the issue.

As far as the bed knife is concerned, please never attempt to remove the bed knife yourself, rather you remove the complete sole plate assembly and the reel and take them to your nominated machine shop and they have the correct equipment to do the removal of the bottom blade and reinstall a new one. Then it has to be machined at the same time as your reel so that they match. You can not just buy a blade and put it on unmachined.

Cheers,
BB

Hello bb

As I'm very new to this kind of mower I may of misunderstood. I'm slowly getting around the terminology.
Lever is in off position I slowly pull the cord the big cone/clutch rotates the shaft on the other side of the green side sometimes tries to turn. Once the mower is actually going I think the force of the motor side shaft is stronger and it makes the other side of the cone spin despite what position the lever is in. Do you think it just needs adjusting or is the inside of it work out. When i do engage the blades it makes a clunking noise and keeps spinning.
I hope that makes sense
Thanks for the heads up about the bednife. I need tondo some research as to who could fix that as I'm from a small country town. May try the local golf coarse.
Cheers
Brendan.

Hi Brendan,

Yes, go and see your local golf course as they are sure to be able to put you on to who they use to do their machines.

I'm getting the impression you still are not understanding what I'm trying to convey to you in regards to the clutch housing running true or not as that is a major part of whether the clutch is grabbing only on a partial part of the revolution when the drive is disengaged. Regardless of that it seems that your clutch cone is slightly out of adjustment and will require the clutch fork adjusting screw to be wound in a bit more, but it can only be wound in to the point where when the drive is engaged that they is a slight amount of clearance between the fork and thrust pad. Also I would make sure that all the clutch parts and associated pieces are well lubricated as that's essential for smooth clutch operation.

Cheers,
BB

Hello bb
Sorry this must be frustrating trying to explain via messages. I'll try again. clutch is in off position. I pull the cord the housing of the clutch turns but the actual cone does not spin and there is no vibration. Once the mower gets going it sounds like the cone /shaft is trying to turn. And it actually starts to turn a little and after 30 seconds the blade ends up spinning. I'll try doing little adjustments on the arm that pushes the cone in.
Cheers
Brendan.

Thanks DJ for moving this thread

Cheers,
BB

brendanandsarah. Im getting the exact same problem with my 20" at the moment and i just bought it. Start it up and the blades are spinning when not engaged. makes clunking noises. Starts fine but after a second or too the shaft virbrates and engages the clutch

Hey mate,

Different person here but im having the exact same problems with my 20" the round part is defiantly wobbling left to right and not straight on mine.