OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Another Scott Bonnar 33 project

Hi,

I picked up a SB33 not working and I wish to put it back to what was designed for. Cut a nice lawn.

Pics of it. Will add detail on a next post

The Kirby engine has some issues:
Start coil broken
Fuel line to carby missing
some Choke parts missing from carburettor
Petrol tank open valve seem stuck
Has very low/weak compression

My goal is to get this machine back to running efficiently and with some reliability and easy of maintenance. So I decided to replace the tired engine. Got a Briggs & Stratton 3HP year 86 I think. Sound good. and Im rebuilding its carby right now.

Replace engine nrs below

Got the engine out and this is where I'm stuck,

I can't get the clutch off the engine's PTO shaft. Removed the 3 bolts and would expect it would split apart. I'd love some tips to remove the clutch with minimal risk to damaging it. Any ideas ?(Note, the sofa is in my mancave/shed not the living room)

Hi,

Where abouts in Adelaide are you located ?

as I may be able to help you out.

That large nut needs to be undone and as you have the engine disconnected from the mower this may make it a tad difficult.

Cheers,
BB.

Hi,

Im located in Parkside close to Unley.

Cheers,
Pedro

After the heat wave passed, I can work again in my shed and the project resumes.

Still have to remove the clutch, I was trying to get a opposite force from the other side of the engine. Perhaps a few more runs of wd40 will do.

Tested engine mounts and seem a perfect match. Engine looks good on it.

Still waiting for a carb kit to get the BS 3HP back to prime time.

Hi,

An update to progress.

The old (newer) BS 3HP is now tuned and running nicely. Good tone. Problem was fuel pump mebrane was hardened. and ajustment screw was too open.




Still fighting with the clutch. Got the bolt out but still stuck.

Hello pfbranco

This is a great topic, with great images.
The approach is to get a decent daily driver - I like that!

The clutch may require splitting and application of a puller to
separate it from the crankshaft.

Many thanks for adding to the Model 33 record.

-----------------------
Jack

Thanks Jack.

I assume you a talking about a this sort of puller:


I dont have one.

Is it mandatory or can be done any other way, I can see an pin that if rusted ho be holding the clutch



While I struggle with the clutch I need to plan ahead next steps, Sharpening Blades

They don seem that bad to me:








Another question is it back lapping easy to do and possible DIY ?

Cheers
Pedro

Hello Pedro

Yes, that's the sort of thing, but Mallet taps on the housing
should be all that is needed. I will ask Mod BB for his thoughts.

Yes, backlapping is easy to do, but this one needs a grind.
I do not feel backlapping will restore the pitted faces now.

---------------------
Jack

Hi,

Some Progress
Got the clutch apart. Had to smack it with a mallet like I stole it

Hi Pedro,

I fully support Jack's advice regarding a full reel spin grind and Bed Knife replacement as the rust pitting is extensive and thus creates issues when trying to grind, especially the bed knife.

Cheers,
BB.

Progress,

After 3 days of WD40,

removed the tank from the Kirby engine, and was able to tap with a better angle. Clutch is out undamaged.

Persistence pays doesn't it, especially when it comes to dealing with corrosion.

Cheers,
BB.

Started reassembly.

To help others with a similar Scott Bonnar 33 model. took picture of the clutch assembly parts, it has cylindrical pin.




Its easier to tap the clutch back in with the slot down otherwise the pin will fall out.



This is how it looks back in. its tricky if you miss align it. I failed first try.



Time to mount the model 33 clutch assembly, and this pops some questions, first is the clutch cone is bare metal with metal. is a cork material supposed to exist in between?

Next is lubrication, I used some grease where the clutch moves back and forth, engaged/disengaged and close to the spring moves outside the shaft, also some oil in moving parts. Is this correct?



I assembled to try and a think I still need to move the clutch half close to the engine an bit closer to the engine. I got so much trouble to get it out that I might have not pushed enough.The clutch seems to slip. Well its part of the learning process..

Machine is running again.




Second attempt clutch still slips, need to dismantle again.

Third try. its good. No slip Will try tomorrow when noise doesn't disturb others.

There should be cork for the cone to grip on to. This will also throw your engine clutch relationship out without it being present.

Cheers,
BB.

Thanks for the info BB, ordered the clutch cork.

Any good places in Adelaide to sharpen the reel? Good value for money.

The best place in Adelaide is "Australian Saws and Blades" on Research Road Pooraka.

Cheers,
BB

Its cutting grass again, this 40 year though like a tank machine is quite fast when you apply drive. I have to walk quite fast and need to get used to it. fist time I operated one.:), proud of the engine tuning done by myself, considering I got it cheap because it was not running properly. Very smooth, sounds like a go-kart or a minibike.



Next is sharpen the blades. hope it is not too expensive an kill the project budget.

Cheers

hi guys, I'm trying to get the clutch of my 33 B&S driveshaft with no luck! My plan is to put the motor on my 45 that is in better condition. The posts above don't detail very clearly how the clutch connects to the shaft when there is no bolt / cotter pin. Any help is appreciated

Here's the other pic

Have you tried loosening that nut?,

Hard to see in the photo but the nut is loose and sitting loose on the driveshaft

You need to use a 3 Jaw Puller to get it off the PTO shaft and not use a hammer at all.

Cheers,
BB.