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

Hi to all who have assisted so far.
The state of play now is that I have received the new clutch parts and painted them up. I have removed the engine and decided to buy a new Honda. I thought the engine shaft look damaged as it had a big gouge out of the side where the cotter pin must have slipped on it at some stage. I wasn't overly happy with the way the engine was performing anyway so decided to bite the bullet. I am in the process of backlapping the reel whilst I have the engine off. I have gained some practice on this on several old handmowers this week and very impressed with the results from what is a simple procedure.
Any tips on reassembling the clutch? I have gone with a grub screw version rather than a cotter pin version. I have a new bearing to install in it and I assume this just taps in with some encouragement?
regards Tim

Hi Tim,

As far as the thrust bearing is concerned just use a small block of wood and use it as a drift to knock the bearing in. Just make sure you keep it rather square when knocking it in. Make sure it is quite well lubed up with a good HTB grease before putting it back into the clutch body.

Also make sure you get the clutch body on the shaft towards the engine so that you have a fair bit of adjustment in the clutch fork adjusting bolt.

From there there's not much more to say but best of luck with it and hope all works well.

Cheers,
BB

Hi BB,
Yes all went pretty smoothly. A bit of fiddling to get the engine back on but the photo attached is the final product. Running and cutting well. Next step is to touch up the red paint on the chain guard plate
and a few other areas. Otherwise I am pretty chuffed that I was able to do this. Thanks for everyone's help!

regards

Tim

Hi,
I happened to read your forum as I was in the process of replacing the clutch thrust pad. I have removed the clutch body and while doing so, the clutch body key came off and did not have a chance to look at how it's fitted. I noticed the key has a slight bend on the other end and I thought this end should fit on the rod coming out of the engine. Any advice/comment on how assembling this ?
Also, I did not disassemble the clutch body as I don't see the need for. Any comments as well ? Photos below.

Hi Shannon,

Welcome to our wonderful Forum where we all learn something new everyday.

Well that is the sign of a well flogged out piece of key steel and as such you might have issues getting it back in where its supposed to be. As such I wouldn't reuse it and just replace it with a new piece which can be bought for around $5 to $6 through the online shop or if you have a mower shop near by you'll get one there. The Woodruf key (half moon shaped)is also showing signs of wear and I'd replace that one too while it's all apart. It's a small price to pay and not have bigger issues later on.

You might want to consider splitting the two clutch halves open and removing the thrust bearing inside and re-lubing it with new grease, as you might as well do it while you have the clutch assembly out, also inspect how much cork thickness is still there so as to avoid an issue that one of our other members had of no cork at all left. Greasing the bearing will quieten the machine down somewhat when it is running with the cutter clutch disengaged and all the pressure is on that thrust bearing. (same as having your foot on the clutch in a manual car)

Just before putting it all back together get a small file and chase out the keyway on the engines output shaft thus removing any of the proud burs that have been created by the key steel, this will ensure that it will all go together rather smoothly.
Also splitting the clutch apart and only installing the engine side first will allow you to adjust the key steel back and forth so that it's in exactly the correct position as it can slide in too far if it grabs onto the shaft when installing the clutch half. This is just a suggestion.

Let us know how you go and once again a huge welcome to the ODK

Cheers,
BB

Thanks BB for your advise and suggestions. I have opened the two clutch halves.
The cork appears to be ok and intact with the inner cone snugly sitting on it. I did not remove the inner cone anymore.
The thrust bearing appear to be so attached with the clutch body and not that easy to remove. I just left it as it is as I could damage it if I force to remove it. I cannot seem to see any signs of grease from the outside. Will it be ok if I just put engine oil around the gap on this bearing ? Also, if I have to use grease, is there a special type of grease I should be using ?
The spring looks ok as well.

Hi Shannon,

Yes there's plenty of cork in there that's for sure.
Normally one would use a slide hammer with an expandable shank that fits in through the hole and then you wind it out to expand, once that is done you just use the slide part to knock out the bearing without any damage. Can't see any other way of doing the job without screwing up the bearing which is quite an expensive little fella.

In your case I would use some fairly heavy oil (the heavier the better) and let it soak in through the opening that you can see between the inner and outer race. Just don't flood it as that creates it's own set of issues. Then after a while rotate it and see if the bearing has taken enough oil to reach the bearings inside and provide the lubrication it should have. You'll certainly feel the difference.

Have you managed to source any key steel yet ?

Cheers,
BB

Hi BB,

Thanks again. Not sure what you meant by heavy oil. Are you able to give me an example brand and type ? I will also try squeezing the grease in the gap and see if it gets thru.

I assume I can use just the standard grease.

One thing I for forgot to mention was the cutter keeps on spinning even if the clutch was disengaged and so I thought this was because of the worn out thrust pad. Will this be correct ?

I have not ordered the keys yet as I though I might need something else for the clutch body. Good that the body is ok so will order the keys thru the online shop.

Hi Shannon,

I'm starting to think that you have a slightly flogged out clutch half as that key steel is a bit of an indication that the clutch half is moving on the output shaft and as such is no longer running true, thus catching on the clutch cone ever so slightly and enough to keep the cutter spinning but without much force. Also a worn out or melted thrust washer is a sign of an untrue running clutch. I notice there is no captive cotter pin and nut in any of your photos, is it missing or just not in the shots ?

If I am to be correct in my observations then to over come this you'll have to purchase a new clutch body of either 5/8 shaft or 3/4 shaft size,( whichever yours is) an engine output shaft key, woodruf key and thrust washer. The newer designed clutch bodies no longer have the captive cotter and alternatively have two set screws that lock onto the shaft at 90 degrees to each other, this pretty much eliminates the problems with the die cast clutch bodies of old.

Slide the old clutch body onto the shaft without the key installed and if there's any play (wobble) whatsoever, there's your problem.

Cheers,
BB.

Hi BB,

I tried installing the clutch body on the shaft. Is it supposed to sit tightly on the shaft without being able to move it at all as I find there is a slight play ?

I'm not sure what the captive cotter pin, nut and thrust washer are. Are you able to refer to the parts diagram and let me know what number it is on the diagram.

I can only find 2 screws that lock the clutch body onto the shaft.

Cheers,
Shannon

Hi Shannon,

Honestly there should be absolutely no wobble of the body on the shaft whatsoever, basically it should be a firm fit with no play at all.

If you have no captive cotter and just the two set screws with square heads on them then that is the latest model body, but it has obviously come loose and started to flog out the centre hole that fits over the shaft and as such this has damaged the key steel piece, from there on it can only get worse and not better. As previously mentioned a new body must be used along with a new key steel to firmly locate the body and avoid it twisting on the shaft, then just put a new plastic thrust pad into the system and you'll be away for quite a few years. Oh I forgot about the thrust bearing inside the clutch body. Most people will buy a new one if replacing all those other clutch components, but if you have access to someone that has the correct slide hammer tool to remove the bearing you should be able to just force new grease into it from the back side of it and then reinsert into the new body.

Hope this makes sense to you, if not please ask more questions as I'm only too happy to help out.

Cheers,
BB

Hi BB,

That's great. You mentioned to use heavy oil on the bearing. I'm not so sure what you meant by heavy oil. Will engine oil be ok ?
If instead I use grease , will standard or ordinary grease be ok ?

Hi Shannon,

If you are going to be able to get access to the rear of the thrust bearing due to replacing the clutch body you can use just a normal wheel bearing grease like Castrol HTB etc.
Also engine oil can be used but grease is my preference that's for sure.

Cheers,
BB