OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Removing clutch and replacing cork

Hi,

I've been rebuilding a Scott Bonnar, actually it's a bastardised hybrid of a green Scott Bonnar and red Rover 45, but I'm not doing it for looks, just a good working machine.

Anyway, it's all running smoothly except that the clutch slips when engaged. I've pulled the clutch apart while still on the shaft and found the cork is broken and not stuck to either side of the clutch. I want to replace the cork.

Problem is I can't figure out how to remove the shaft and clutch. I figure I need to remove the sprocket on the end, but to do that I need to remove the bolt holding it on, but the shaft spins both ways so there's nothing to get resistance against to remove the bolt, it just spins. Any tips on how to remove this?




Thanks,

Paul

If you want to remove the sprocket I suggest you just hold the shaft with a pipe wrench while you remove the nut with a conventional spanner. You'll have to remove the chain before you slide the sprocket off, unless the chain is worn out. There should be a joining link - I think I see it toward the rear of the mower about 1-1.5 inches down from the sprocket.

Thanks Grumpy,

Managed to remove the bolt, can't figure out what to do next. The clutch wont slide far enough down the shaft to get off the engine crank, is it supposed to?

Paul, I've never worked on one myself, but from other threads I understand you need to slide the other half of the clutch off the end of the crankshaft, so the clutch is treated as a single piece. Then you can slide the shaft and clutch to the left far enough axially to move the clutch forward far enough to go past the engine, so it can slide to the right. In other words, take the whole clutch and shaft off together.

To remove the clutch from the crankshaft, look for a cotter pin nut. Undo it two or three mm and tap the nut end of the pin gently once with a mallet. The cotter pin is a captive type - it does not come out, in either direction, but it unclamps the shaft when you tap it. It will then have slight movement axially, showing it is loose. The clutch may be stuck on the crankshaft by corrosion. If so, tap it axially on opposite sides with a mallet and/or carefully use a lever between the clutch and the engine. Be gentle - the engine, especially, is fairly thin cast aluminium.

you have to take the engine off to get the clutch shaft off, there is no other way, there is about a 1 cm gap between the engine shaft and the clutch shaft, so there is no way that you can undo the clutch housing to remove it.

you also have to undo the small housing that attaches to the end of the cluctch shaft, the one that wont slide either way, as there is a bearing in there that is pretty much sealed to the shaft.

so undo the engine, and teh clutch housing and every thing will slide stright out no problems

Thanks guys,

Grumpy, I don't think I have a cotter pin, I have two square headed bolts attaching the clutch to the crankshaft. I have undone these and can move the clutch about 1cm away from the engine, doesn't seem to be enough though.

Tezza, sucks if I have to remove the engine, sounds like a lot of work. I have undone the small housing on the other end of the shaft, but it just spins, like you said, must be a bearing attached to the shaft.

G day!! all Paul going by your photos u are close, if u cannot get the engine clutch housing of the engine shaft i would leave the shaft side of the clutch housing alone and just remove the engine with the halve intact on the shaft when u have done this u will have access to the engine clutch cone and will be able to fit a new engine clutch cork attached is a photo regarding above said kind regards steve...

Paul, deviosi's method will work, and is probably easier than tezza's. Removing the engine is essentially 4 bolts and a throttle cable.

Hi Paul, and a warm welcome to the forum. It's good to have another Scott Bonnar owner on board.
I too agree with Steve's (deviosi) method and removing the engine is easy-peasy, a grumpy has mentioned, just 4 bolts and the throttle cable, and leave the clutch shaft intact. Remove all traces of the old cork and glue.

The adhesive that Steve uses is perfect to glue the new cork lining, and use the clutch inner cone with clamps (as per Steve's method) to hold the new lining in place as the adhesive sets.
Please let us know how you get on.
Paul, once again,

Thanks all for your help and warm welcome

Had look last night and it looks like the engine is pretty easy to remove, so will have a crack at it this weekend. I've got two mostly complete mowers, so I might just swap over the clutches for now and then try fixing the worn one. Where can you purchase new cork? The cork in it is not too bad, it's just in two parts and not glued, so I guess I could just glue this back on. Looking at an old post I'm assuming Kwik Grip is the commonly accepted best adhesive?

One of the reasons I have two mowers is the first one I brought (green Scotty in second photo) doesn't have a solid rear roller, it's roller is in two parts each about 10cm wide, anyone seen this before? Seems odd to me.

Finally a big thanks to you regular posters on this forum, while trying to swap the blades / cutters between each mower I couldn't get the sprocket off the shaft, it wasn't till I read these forums I learnt about a gear puller which made my life a lot easier.

hi Paul! most good mower shops keep scott bonnar clutch corks,catcher blocks, reel bearings. Small cost big gain replacing the damaged cork kind regards steve....

Removed engines and swapped the clutch over from my spare parts mower yesterday, worked perfect.

Thanks again for your help.

Good one Paul, great to see that it has gone well for you.
I agree with Steve, replacing the cork is the best option, and their cheap...As this thread is complete, I will now close it.