OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Solid Engine Deck Series 1 Scotty 45's

Hi to all ODK members,
I had a very interesting chat with the proprietor of a Western Australian mower repair shop this morning, and found out some interesting information on the solid deck Series 1 Model 45 Scott Bonnar.

It has been a long held belief here at ODK that the solid deck Scotty's were far superior to the Series 2, twin rail models, due to the cracking problems of the rails adjacent to the engine mounting holes.

Well, it turns out that the solid deck was not all it's cracked up to be (no pun intended, ).

The fact is that this gentleman has had to repair many, many solid decks due to serious cracks adjacent to the mounting holes to right through to the front of the deck.
The cracking problem is just as prevalent in the solid deck as the twin railer.
So it appears that engine vibration is the cause and has been inherent in the Scotty design since its inception.
As I've said before, you learn something new in the Scott Bonnar story every day.

Sadly I've found that out

Interesting that the crack seems to mainly stem from the outboard engine mounting bolt. With twin-rail SB45s I normally expect the crack at the inboard bolt.

We need to get more information on how many cracked single-deckers are around, versus how many cracked twin rails, and whether there are any cracked rails on mowers that came from the factory with set screw engine-side clutch halves, versus the old captive cotter type. At the moment I haven't heard of a crack on a set-screw mower.

Hi to all ODK members,
Trying to find out numbers would be hard to do...the gentleman I spoke to said he had repaired cracks in stacks of solid deck Scotty's....as well as the twin railers.

The set-screw modification was a Rover innovation, and no single-decker was ever fitted with that straight from the factory. They were all captive cotter type clutch halves.

The question to ask is this:
How many Rovers (they are all twin railers) are out there with cracked rails?

I guess the bottom line is the single-deckers have a cracking problem...
Seeing that is the case, are they more collectible than the twin railer?....

Well here's a cracked Rover in my boneyard..


The solid deck machine from my previous post is also cracked badly at the rear of the deck..

I can only remember seeing one cracked single deck in our archives before, compared with quite a few twin rails.

Is there any way to find out for sure whether that Rover had set screws or a captive cotter?

Hi grumpy,
Here is the proof...Set screws was the go.
Please scroll to page 9.

That page is dated 2004, Deejay. When did the Rover 45 begin production?

I bought the Rover pictured with cracked rails to strip for parts and it had the grub screw clutch. Judging from the paint (which matched other parts of the machine) it was original. The Briggs engine fitted also looked original and was built early '93. I also have another Rover 45 which is definitely original with a Briggs build of late '93 with the grub screw setup also... but no cracks

Hi Michael and grumpy,
That ties into the info I have also...

The proprietary company Rover Mowers (Australia) Pty.Ltd. aquired Scott Bonnar limited in 1980 with Rover as the major shareholder. An export division was left in Thebarton, South Australia until 1983 when the factory closed and relocated to Brisbane.

In 1981, the new company was named Rover-Scott Bonnar Ltd. and was so named until April 1992 when the name officially changed to Rover (Aust) Ltd. They were still producing machines badged Rover-Scott Bonnar at this time, as far as I am aware.

I am led to believe the first machines badged as a Rover were produced in late 1992 or early 1993, but I have been unable to substantiate this, as my records don't have an exact date for the change.

Thanks to Michael, 1993 looks very much like the year of the change.

Hi Deejay,

Seems like you had a interesting talk. I agree with you that Engine vibration is the main cause for cracked frames. Does not matter wether you own a solid deck or twin rails frame.

From you talk did you have any numbers on the breakdown on cracked frames repaired; Solid decks vs twin rails?

Also the repairs made to cracked frames are your comparing 20" single deck against 17" twin rails?

When I was looking to purchase my scott bonnars, just about every 17" twin rail had cracks around the bolt holes. So my conception being that both forms of frames do crack, but there is more examples of twin rails than single decks. This may be due to the mass volumes of twin rails produced over the single deck.

p.s Out of interest, what are the thickness of the single deck and the twin rail decks?

Hi SBM45,
In regards to the discussion, no, we did not talk specific numbers...the gentleman said he had repaired many, many solid deck machines suffering from cracks.

No we did not talk specific machine sizes...It was just a general discussion, on all things Scott Bonnar, including some history of the company.

Never having owned a solid deck Scotty, I don't know the thickness of the deck...Maybe one of our Scott Bonnar Series 1 owners may be able to answer that question.
PS. We did not discuss Rover mowers at all.