OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Scott Bonnar 45 restoration - where do I start?

Hi all,

First time post here, so I'll begin by thanking you for having me along on this very informative forum.

I am a long-term kikuyu owner and have it for both my front and back lawns here in south-west Sydney.

I scarify every year, always in late September and sometimes again in late March / early April, depending on how much thatch and sponginess the lawns develop during a Sydney summer. I have had my trusty Honda 4 stroke for the last 12 years or so, and combining regular mowing with watering and fertilizing, I do try to keep my lawns respectable.

Last week a neighbour and I were chatting about lawn care etc. The subject eventually moved to roller mowers and how I had always wanted to try one. Rob mentioned that he had one in his garage which had sat idle for over two years. One thing led to another and now I am the proud owner of a 40 + yr old SB 17 inch 45 roller mower (in need of some work).

I am not a mechanic but have a healthy interest in machinery and maintenance cycles etc.

Having had an initial poke and prod around the SB 45, I am beginning to commit myself to a full restore - a new 3.5HP Briggs and Stratton engine at least, possibly a new catcher box and blade reel. I am aware that there are issues with the carb as a steady stream of fuel leaks from the float bowl area, so at this stage I have no idea about the state of the engine. A new engine might not be a bad idea anyway, as the current engine does look like it has seen better days.

The twin rail chassis appears to be in good shape - no visible cracks. A few expected signs of wear and tear on the sprocket cover were found and the catcher has quite a few dings and dents. The front and rear rollers appear to be good, no squeaks or resistance from worn bearings has been found yet.

I have managed to ascertain that parts are readily available for the SB 45 so I have no issues there.

My first question concerns tearing down the chassis as I am leaning towards the idea of a total ground-up restore. Without falling into the trap of getting in too-deep too-quickly, is there an online guide available to help me walk through the restoration process?

The current 6 blade reel is in dire need of some TLC. One or two blades are bent and all the blades are very dull. If the reel needs to be replaced, should I go with another 6 blade reel, or would a 10 blade reel be the better option, given my lawn is kikuyu and not couch?

Ideally I would like to be in contact with members who have completed their own SB 45 restore projects. I am a beginner - green as grass if you'll forgive that pun - but I am keen to learn as I go.

Thank you for reading my long winded intro and I hope to learn a great deal from like minded roller mower owners.


Cheers, Paul
Sydney, Oz.

Hi Paul,

First a big warm welcome to this fabulous wealth of information that we cal the ODK Forums.

As you have noticed I have moved this thread to the SB section of the "Repairs and Maintenance" sub-forum where it will be of much better use to new members and also existing ones as the "Lawn Care section" is merely for in-depth turf care stuff only.

I must admit that what you are about to embark on has been covered over and over again on the platform and I'm sure you pretty much get all your info from previous members who have embarked on exactly the same thing as what you are about to also do.

The best thing you could do at this stage is take quite a few good close up and general photos so that we can get a good idea of what needs to be your starting point.

So for now, Welcome to the wonderful world of the Model 45.

Cheers,
BB.

Hi Folks,

Thanks for correcting my posting error Bonnar_Bloke. I will know better next time.

I should have thought about posting a few pics of my 45 in my original post. Please forgive me, I am a mere newbie.

Hopefully I've worked how to attach the pics...

Cheers, Paul
Sydney, Oz.

Hi Paul,

Firstly thanks for posting the photos.

I'll have to say this one has me quite intrigued as it's colour is somewhat unusual. It still looks like one of the very last Adelaide built machines, but already sports a new Eagle Farm built ID plate. Sadly we can't read anything from it as all the screen printing is now illegible.

I'd say it's got a hammertone finish on it which suggests Adelaide but we're lead to believe that the first Queensland built machines may have still been painted while the powder coating line was still being finalised. I will say you are far better off with a painted unit opposed to the ill-fated Powder Coating that they had in all the later Eagle Farm built Kermit Greens and Rover Reds.

Your machine has at some stage been re-powered with a Tecumseh engine replacing the Original 3HP Briggs power plant.

I will say that these single vertical thumpers aren't that kind on the chassis rails opposed to the newer style sloper engines like the Honda's and new Briggs engines. These are far kinder to the rails and reduce the issue of fatigue cracking.

Cheers,
BB.

Hi BB,


Thanks for replying.


As far as the origins of my mower are concerned, I simply have no idea.


As mentioned earlier, I am having thoughts about doing a complete ground-up restore. The Tecumseh engine is going to get replaced. At this early stage I am considering a brand new Briggs & Stratton 3.5HP as it will be delivered with the carb and exhaust etc.


I just ducked out to the shed now to take a closer picture of the rails where the engine mounts on, and sure enough there is a crack in the rail. After I get the teardown done and the chassis media blasted, I will need to find someone to weld up the cracked area. I imagine it would be a good idea to get a piece of metal welded onto the underside of the rail where the crack is, yes?


While doing the picture attached, I also noticed the reel and bed knife have remains of red paint on them. Perhaps that may help uncover the origin of my machine a little more?


Cheers, Paul
Sydney, Oz.

Hi Paul,

Is the finish inside the chain case identical to the outer colouring of the machine by any chance ?

I was going to bet London to a Brick that you were going to find fatigue fractures one the engine had been removed. Repairs must be done very carefully by someone that totally understands metal expansion and contraction as that will be the chassis' biggest enemy during the welding process.

The best method to date we've unearthed is the "Jones Gusset Repair method"

Check out the following thread.

https://www.outdoorking-forum.com.au/forum/u...e-double-sb45-restoration.html#Post64558

Cheers,
BB.

Hi BB,


Thanks for the reply. I haven't had the chance to pull off the chain cover yet... I am a shift-worker, currently on nights. I hope to get out to the shed and confirm the state of the chain cover asap.


Thanks also for supplying the repair link, it is very informative and will help a lot. The rail repair process outlined by the Jones Gusset method looks like the ideal solution. I need to find someone in the South-West Sydney area who can do this repair work. Are there any suggestions please?


I also wonder if there's any advantage between having a twin rail chassis versus a solid deck. Do solid deck 45's also suffer the same cracking issues?


Speaking of vibration cracks, I've seen one or two photos where owners have fitted new engines. Some of these engines have the cylinder pointing rearwards at 45 degrees instead of the more traditional vertical design. BB, you mention that these sloper-style cylinders are not as damaging to the rails. Can you offer any suggestions for a suitable sloper-style replacement engine? Would a 3.5HP engine be too much for the twin rails to handle?


Apologies for all my inane questions...

Hi Paul,

As far as quality welders in Sydney are concerned I can't help you there, but maybe someone from that neck of the woods could hopefully chime in.

Yes Solid decks have also been known to crack, but no where near as easily as the twin railers do.

The current 3.5 Briggs sloper engines are quite good and are no where near as rough as the earlier style upright older Briggs designed power plants were.

I've recently bought one myself and installed it on my 20 inch Solid deck and it's probably the best improvement on the machine that I've experienced.

Cheers,
BB.

Ok, thanks for the sloper engine info BB, your knowledge and experience is very useful and I greatly appreciate you sharing it.

Was there any noticeable difference in vibration between the sloper engine and the vertical?

Hi Paul,

Absolutely was, this is the best value for money engine currently available. Generally around the $250 mark if you shop around as many dealers are offering them at this figure to move stock quicker.

If I had a non fractured twin railer I would be swapping over to this model engine so as to preserve the chassis as with the older style thumpers the inevitable will happen, the situation would be "not if" but when.

Cheers,
BB.

Hi BB,

Ok, here's few more pics.

The inside of the chain cover had a decent layer of dried up grease and oil around the perimeter, so I gave it a wipe over before taking these pics. Having looked closely at the chassis sides, I now wonder if the mower has been repainted at some point. You can see evidence of darker paint underneath the slightly lighter top surface, especially around the upper end of the slot for chain tensioner.

I'd also like to ask about two other areas. The bearing case for the drive shaft seems to be a sealed unit as I cannot see an oil hole. is that normal?

Also wanted to show more pics of the catcher. Given the amount of damage shown, is it worth sending to a panel beater or would I be better off getting a fresh catcher?

Hi Paul,

Now this has me somewhat rattled. The evidence of darker green underneath points toward it being a much earlier machine than what we think as Alpine Green finished around 1977 when it was superseded by Apple Green. Now the thing that puzzles me is that Rover ID plate which to date I've never seen one fitted on and Adelaide built machine, but then I'm always open to points of evidence that haven't shown up to date for me. I've always felt the Rover style Ally plates were not used until production continued at Eagle Farm, Queensland following on from the end at the Holland Street premises in Thebarton, SA.

As far as the Transfer shaft bearing is concerned Rover changed to a sealed unit and this reduced more costs opposed to the previous self aligning bearing that was used in the earlier SB Model 45's. Note the oiling hole is missing in the housing.

Everything seems to point to an Eagle Farm built machine here, but the darker undercolour that you have revealed is still somewhat puzzling.

Cheers,
BB.

No harm in getting a quote for a new catcher, but don't be surprised when you see the price. It is fairly well used as can be seen.

For me, it comes down to what the machine will be used for. If it's an every day machine, you can knock out the obvious bits yourself and slap some fillers in the rest, but if you're going for a showroom finish then a new one will be more economical and far better looking.

TC.

There is a chap that's registered on this site called "SB Obsession" that also is a seller on eBay and his father-in-law Denis makes very faithful reproductions.

Here is a link to a current listing of Jason's,

https://www.ebay.com.au/itm/Scott-Bonnar-Rover-45-Catcher-17inch/312407270154?hash=item48bceca30a:g:7qUAAOSwnCdcSYu~

Cheers,
BB.

Hi all,




Cheers BB, Is the darker undercolour the apple green you mention, or is it the lighter top coat? I wonder if the previous owner has repainted this mower at some point? Rather than strip it all back to bare metal, it seems to have been simply painted over. Not that it matters now because I will be getting the whole lot sand blasted and repainted after the rails get repaired.





Thanks for your input TheCount, I didn't know if the catcher I have is recoverable given the extent of the damage. I am planning to use this SB45 as a groomer, so a ground up restore with everything all shiny and new will be my aim.




Excellent link BB, thanks for sharing this info. I am currently putting together a mental list of prices for the bits and pieces I will be replacing. Then I need to work out how to present my findings to the "Minister of War and Aesthetics".

Sadly these things don't restore very cheaply do they and the winners are these eBay part sellers that load the prices way over the top compared to the price that they obtain them for via GA Spares.

Cheers,
BB.