OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers SB 45 cutter clutch slipping

The clutch on my SB45 has started slipping badly. I found a thread about adjusting the distance between the engine and the clutch to about 1 cm to improve the "clamping force" and have followed the procedure to no avail.
Is there some way of increasing the clamping force of the clutch without dismantling everything and replacing the cork?

Hi Beammeup, I'm not sure what this term 'clamping force' refers to....the operation of the cutter clutch is fairly straight forward...the clutch cone is moved by the forked lever and thrust pad inward to dis-engage and released to engage... you can adjust it by the bolt and locknut underneath the cutter clutch handle.. it adjusts the throw through the forked lever by contacting the clutch lever so as it 'over-centres', the clutch dis-engages.
If the clutch cone has fully traveled to its outer-most position (fully engaged) and is still slipping...the clutch cork lining is cactus and must be replaced. No amount of moving the position of clutch to engine distance, will rectify the problem.

Thanks Deejay.
The cone has indeed moved to the outermost position and there is still slippage...so it looks like a new cork lining is needed. Is the spring usually also replaced in this operation?

By 'clamping force' I was referring to how tightly the cone pushes into the clutch housing to produce drive. I suspected that the spring might have lost tension or something like that if the problem was not the cork itself. Cheers

Hi Beammeup....no mate, the clutch cone does NOT push IN to the clutch housing...It comes OUT to drive....and the spring pushes it out as the cutter is engaged....I just hope you haven't damaged it, by forcing it inwards....
If you haven't got one, a manual may come in handy for you to read before doing adjustments....There's one in the Parts Lists and Manuals area...(subscription required).

Thanks Deejay. It seems we have a problem in semantics. My apologies. I have understood what you said and have done no damage. The spring pushes the cone away from the engine and hard into the right half of the clutch housing. When the spring is fully extended the cone protrudes as far as possible to the right of the shaft (looking from the front). I get this.
My question is that since it is slipping, should I just replace the cork, or is the spring loosing tension also a common problem and therefore wise to replace the spring while I have it all apart? I hope this makes what I am getting at clearer. Cheers

Hi again Beammeup, Sorry if I misread your intentions...

The cork lining runs around the periphery of the inner section of the right-hand clutch housing, (looking from the front)...and suffers frequently from what is commonly called 'glazing'. You may be able to rough it up a bit to get it to work, but it is worth the trouble to replace it....saves you having to pull it down again at a later date.

It is not a hard job to replace it; (just a pain to remove the old cork and adhesive) and as you have asked; it is a good idea to replace the clutch spring whilst it is all apart, as they are not expensive.
Also it is a good idea to check the clutch thrust bearing as well for serviceability and replace if necessary.
Any probs just ask and we will step you through it.