OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers SB45 Cutter Clutch Engaging Automatically

Hi All,

Not sure if this is the right place for this thread as it probably relates more to 'Repairs and Maintenance' for a reel mower - and I didn't notice a section for this. But I am hoping someone may be able to help me. I have a SB45 17" reel mower (that I am still intending on restoring some time soon!).

Lately (the last 4 or 5 times I've used it), I've noticed what I consider to be a fairly serious issue, that seems to be getting worse. Essentially, the cutter reel engages even when the cutter clutch handle is disengaged. It seems to be an issue with engine vibration as initially it happened at high revs (and presumably maximum machine vibration) but it now occurs even when the engine is running as slow as possible. I can actually see the reel 'twitching' when I disengage the clutch, and at full revs within about 10 seconds the cutter reel makes a 'snapping' noise and kicks back into full spin (even though the clutch lever is still in the disengaged position). I feel it's a bit of a safety issue, and now when I empty the catcher or wheel the mower over concrete areas, I have to actually kill the engine, rather than just lowering the revs and having the cutter disengaged.

I've had a cursory glance and I suspect it may have something to do with the adjustment of the cutter clutch and the engine drive shaft, but unfortunately that's about as far as my current knowledge will take me. I did notice what seems to be a noticeable amount of free movement in the cutter clutch lever from full vertical (disengaged) to the right (if standing in front of the machine looking at it) - i.e. the opposite direction the clutch lever is intended to move. I've also noticed the screw directly beneath the engine half of the cutter clutch - does this have anything to do with the issue? I also noticed what I thought may be a bit of wear on the clutch lever where this screw meets it - it appears to have ground the surface flat (unless this is originally how it was manufactured). I have attached some photos below, so hopefully they describe better what I am talking about.

Has anyone come across this issue before? Is there an easy solution? I am intending on doing a full restore to this mower, so if the issue is difficult to repair I am considering just packing the mower away until a time comes where I can complete the full restore and hopefully diagnose the problem in more detail.

Appreciate any thoughts or advice. Thanks in advance.

Kenny.