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

Hi Guys,

I am new to the forum as a poster but have been a reader for a while now. Firstly...you have a great forum going. I bought a Scott Bonnar 45 about six months back but haven't used it through winter or spring. I just tried testing it out the other day and the drive stops spinning under load. I figured it might be the clutch and I would like to get the mower working well. I would also like to get the reel and bed knife sharpened and adjusted and I wondered if you guys could recommend someone in Melbourne.

I will post some pics tomorrow.

Hi dramapig, and a warm welcome to the forum. It's always great to welcome another Scott Bonnar owner on board, as we all like to learn new things and tinker here!

Instructions for posting pics can be found HERE

Instructions for removing the cylinder reel and soleplate can be found HERE


The best way to find a good engineer/machinist to sharpen your reel and bedknife, is to contact your nearest Lawn Bowling club, speak to the greenskeeper and find out who sharpens their reels....Greenskeepers are usually a friendly bunch who will help you.

Looking forward to seeing the pics of your Scotty, once again.... to OutdoorKing.

Hi DeeJay,

Just on a side note, many Bowling greens are going away from genuine lawns and are putting down synthetic turf, thus eliminating the services of a greens keeper and water bills.

The chap I use for my reel and blade sharpening has lost quite a few bowling clubs off his books due to this issue.

Just thought I'd bring that point up.

Cheers,
BB

Hi BB,

I have a good mate who is a greenskeeper and lays new greens (both bowling and golf on the coast of NSW....He is at present pulling out heaps of synthetic greens of many Bowling Clubs and putting grass greens back in....Synthetic greens are not all their cracked up to be and suffer from many probs, that grass does not.

Maybe that will happen in Sth. Aust. in the long term.

Hi DeeJay,

I can only hope as I hate synthetic grass, it just doesn't look real does it ?

Cheers,
BB

Hi Guys, thanks for the warm welcome and for the quick responses. I found a company in Cheltenham called ADE Turf that service pro greens keeper equipment including reel grinding...not sure if they are any good. Cheltenham is a bit of a hike from me so I think I will try Deejay's recommendation first and contact the local bowls club. I managed to take some snaps of my SB this afternoon so here goes...












The mower has obviously had a Briggs & Stratton motor added and the old one replaced. I have the manuals for both.

ADE Turf certainly have the top-end gear for cylinder/bedknife grinding.

However, it's likely that they aren't the only firm who do, in the Melbourne metro area, so see if there's someone closer to you. You may have to balance convenience vs. price, though.

There are some 'bitsa' aspects to your SB45. For one, it has the captive cotter main clutch body, which was never OEM fitted to Rover-plated 45's.

Hi Gadge, which parts are you referring to? Just the clutch?

Hi Gadge, just a gentle heads-up mate, this machine could be what we describe as an early "transitional" machine...as it wears the ID plate from Rover-Scott Bonnar...and may have employed NOS Scotty parts in its construction...We have seen that on the forum in the past.

Seeing that the Briggs has been replaced, without the Model, Type and Code for the original engine, we may never know the approximate date of erection of this machine.

No worries Deejay, I was confident I'd quickly be corrected by one of the true SB experts here, if I had it wrong!

Hi Gadge, DeeJay and Dramapig

Firstly I'm not trying to push anyone while their down as that's not my style, only helping here I hope ?

I'd be pretty confident that the clutch is more than likely the last of the Alloy type captive cotter units that were used still in the early Rover days until the twin set screw unit was designed and put into production around the time of the full Rover 45 machines.

Gadge is probably in the mindset of the earlier cast iron captive cotter units that are nearly indestructible until hit with a hammer by a novice. They are the biggest gold nugget on the early SB units and I'd crawl over hot coals to gain more of them.
If you look closely at that photo you'll see that both clutch halves are alloy, which indicates it's of the later variant.

BTW Just finished a job this morning on a cast iron unit that had the cotter done up too tight and then hit with a hammer by some novice twitt (previous tenant as DJ calls them), lucky I just happened to have a spare cast iron unit on hand to keep the 20 inch solid deck all original.


Cheers,
BB

Hi Guys, would it be worth me stripping the clutch down (thanks to Deejay's videos) and posting photos? I must admit that I now feel a little disappointed with my mongrel SB

I new the motor wasn't the original...looks like it might have come with a Briggs & Stratton 60152.

I would rather fix it myself if it is not too difficult.

Hi Dramapig,

Before you start stripping it I would check the adjustment on the clutch cable at the chassis end, 9 times out of 10 that's where the issue lies as clutches do wear and do require adjustment.

I'm in a bit of a rush now but will answer somewhat better when I return

Hi bonnar_bloke, I didn't see your previous post when I posted my reply. I tried adjusting the clutch cable but didn't get any love. I will have another look at it during the week then. Thanks for the advice.

Hi Dramapig,

Is there any slippage in the initial drive shaft clutch which is located at the end of the engine output shaft or is it just slippage in the drive train (mobility) itself ?

Cheers,
BB

Hi bonnar_bloke, I think it is in the drive shaft end as the entire drive stops spinning. If I adjust the revs or tilt the mower back it seems to re-engage intermittently. I tried adjusting the chain tension but that didn't make any difference. I will take it for a spin tomorrow and video it so that I can check afterward. I can post the video on youtube if necessary.

Hi dramapig,
What we don't want is for you you to go adjusting things 'ad-hoc'; This can lead to other problems resulting from your lack of knowledge, (which we entirely understand) and can give you a false reading of what is really the initial problem, and cause further damage to your machine

What we really need, is to have you on the same page as us, with regards to the correct terminology as to the drive train of your machine as such...
Here are the salient points:

(1) The cutter clutch is the one that is directly connected to the Engine PTO (Power-take -off) shaft on the right hand side, (looking from the front), painted black, round; secured by 3 screws with a nut looking at you on the inner side, ( the captive cotter-pin) when you rotate it..
This is where I believe your problem is....

(2) The land-roll clutch, is located in the chain case, and is located in the chain-case under the removable cover on the extreme right-hand side (looking from the front) behind the largest sprocket in the bunch...this is the system that drives ( self propels) your machine across the lawn...and engages when you squeeze the left-hand lever on the left-hand handle bar.

As you have adjusted this...it may need re-adjustment to correctly position it back to where it was initially.
Similarly, the primary chain tension adjuster may have to be re-positioned to where it was initially....there must be 1/2" play in the center of the chain (roughly) and definitely not tight, this is the chain that runs to the cutter sprocket (the double one that connects to the cylinder reel) from the small 12 tooth (little) sprocket that connects to the engine PTO shaft.

Now that we are now on the "same page" as far as terminology is concerned, we can proceed to your problem...What I need to know, is exactly what is happening...Can you post all the symptoms that is occurring as you are trying to mow?

As what you are posting at present, doesn't explain your problem.
I will personally help you sort it, if you can tell me what exactly is wrong....Using the correct terminology as I have explained....If that makes sense!
I will get to the bottom of it....

Hi Deejay, thanks for clarifying the terminology and I certainly don't want to stuff the machine up by adjusting the wrong things. That said, I am not a complete nube with regards to motors and chain driven equipment so I had a reasonable suspicion that the cutter clutch is the issue...hence the post. I will run the mower again tomorrow and report back. Thanks for all your help as I am a complete nube when it comes to the cylinder mowers.

Hi dramapig, and thanks for reporting back.
I will look forward to your post, we can then proceed to get your machine sorted.

Hi Deejay, Sorry for the delay getting back to you. We have had some atrocious 40 degree days with strong winds here so have been unable to work outside. I reset everything back to the way it was. Symptoms are...when I engage the clutch lever the SB starts to move and the cutter clutch and engine shaft start spinning (as to be expected). After a few seconds or under any load, the cutter clutch outer cones continue to spin but the inner cone stops as does the engine shaft, chain, cylinder etc. I haven't touched the cutter clutch yet but thought it might be the inner cone lining. Happy to take advice from you though before I do anything. It does look like the cutter clutch is alloy.

Hi dramapig,
OK, what we need now is some pics of the cutter clutch cone, one with the clutch is fully engaged (ie. in the position it would be when cutting grass) and one with the cutter clutch disengaged....I want to see particularly how far the clutch cone extends past the outer ring when it is engaged, and how far it is pushed in when disengaged. Thanks mate.

Instructions for posting pics using our forum Inline Uploader can be found HERE
Looking forward to seeing the pics,

Hi Deejay, photos are attached.

Clutch engaged

Clutch disengaged

Thanks for your help and let me know if you need more info or photos.

Hi DeeJay and dramapig,

Just my observations and that is the engaged picture shows (just) that the clutch fork may still have the slightest pressure applied to the thrust washer clutch thus allowing the clutch to slip under load. I've always adjusted the clutch fork so that there is ever the very slightest amount of play between the fork and the black plastic thrust washer, thus from there you have total clutch contact, but I'll leave it to DeeJay to make the final call on this.

BTW just an observation and it looks like there hasn't been much lubrication applied around the thust washer area for some time.

Cheers,
BB

Hi to dramapig, and BB,
And my thanks for posting the pics, and for BB's observations, regarding the thrust-pad.

They say pictures say a thousand words...and there is no exception in this case....The problem is with the clutch cork that is glued to the inside of the outer clutch-half...or should I say lack of it!

I believe that would explain all your symptoms, as the cork has most probably worn well past its used-by-date.

I have come to this conclusion because of the excessive protrusion of the inner clutch cone when it is engaged, and not depressed far enough when it is dis-engaged.

Here's your pic of the excessive protrusion:

Clutch engaged....

Here's mine....
Clutch engaged....

Here's your pic of the clutch cone not depressed far enough to dis-engage:

Clutch disengaged

And here's mine...
Clutch dis-engaged....

You will need to follow my "Engine and Clutch Removal Guide" HERE and remove the cutter clutch assembly and examine the clutch cork....and replace it. You will have to remove all of the old cork carefully and all traces of the old glue...Eucalyptus oil may help with the glue removal, then you have to remove all trace of the oil....'Prepsol' (wax and grease remover) is excellent for that!

The replacement cork can be found HERE

This is the method of gluing the new cork in place and the recommended glue for the purpose...


Here is a pic of a used cork in place, with heaps of life left in it....for comparison with yours, after removal....

Good luck, and please keep the pics coming....

Hi Guys,

Well I guess I'm going to say that "2" pictures are worth even more ! Well spotted DeeJay.

I must admit that I initially thought that the cone was out too far but the the wife distracted me about going out and being rushed I overlooked it. From looking at the A~B comparison shots dramapig's clutch must make some horrific noises when activating the lever as there is probably no cork left on it at all and she's metal to metal with that amount of protrusion.

If there's one thing I've learnt and that is that when you don't have the item right in front of you to operate and look at constructively then sometimes one overlooks things that are just so plain and obvious while looking for something much more sinister and hidden.

Again well spotted DeeJay and that's why you're the "old Master" on here !

Hi BB, and Dramapig,
There is an old saying that goes something like..."At times you can't see the wood for the trees"....Don't belt yourself up too much BB, we've all done it at ODK and the best part is, this is how we learn new things....

You will often hear me say to new members..."We all like to learn new things and tinker here"...You have imparted your great Scott Bonnar knowledge, that you have gleaned from your experience with the marque, to many a 'newbie', but sometimes occasionally, it takes a fresh pair of eyes to spot the problem....

This is what ODK is all about...helping our members sort their probs....in a friendly, professional manner...You do that all the time, and is much appreciated by all concerned....

To Dramapig, let the adventure continue....

Hi Deejay & BB

Thank-you both heaps for your time and expertise. The cork makes a lot of sense; I will order some today and post pics as I go.

BB I will definitely get onto lubrication after I have sorted the clutch out.

I might take a video of what I am doing just in case. Thanks again guys

Hi Deejay, I watched your video again...very thorough

One problem, I cannot budge the captive cotter pin. It is difficult to tap as the cutter clutch is hard up against the motor. I don't want to hit it any harder as I am scared I will damage the engine shaft. I have already flattened the head of the nyloc nut.

Any suggestions?

Update...the captive cotter pin moves upward but won't drop down at all. I've disassembled the clutch and as suspected the clutch cork was destroyed. It wasn't attached and it had broken into pieces. The spring still has plenty of tension and the and the inner clutch cone looks ok, but I'll let the experts make that call. I'll post some photos later once I manage to get the main clutch body off the engine shaft. Damn that captive cotter!

Hello Dramapig, Administrator Deejay, Technician BB and others

I interrupt here because this is turning into a great topic for the "101" of SB45 primary clutch removals.
Dramapig (what a great name!), the captive cotter will not "drop down" because it can't.
It's just like the cotter on a bicycle crank. You tap the pin to "release" it.

Once 'released', you need to tap the engine side of the clutch housing to move it off the crankshaft.
In most cases it will move freely and easily. It is only then that the cotter can be removed.
It is no longer 'captive'.

All very interesting.
------------------------------------
JACK.