OutdoorKing Repair Forum Forums The History Forum Model Histories SCOTT BONNAR Models ENGINE - MODEL 201 - c1958

Hello ODK History Lovers
The great Scott Bonnar Company from almost its beginning sold power mowers.
These were electric. In the 1930s they introduced their first petrol-powered
machines. Some engines were sourced locally, but many were imported too. Then,
in the late 1950s, when the rotary revolution was in a spin, Scott Bonnar took
the bold move to make its own engine - the Model 201.

Malcolm Bonnar recorded in his 1971 Memoir under the date 28/12/57: "The first
100 engines we made in the Factory. These engines look like turning out trumps
if the cost can be kept down." The Model 201 was Scott Bonnar's only engine -
a 2-stroke loop-scavenge design of 155cc.

It may have been a matter of pride that Scott Bonnar entered engine manufacture -
other AUS mower companies had done it successfully - and at a time when Scott
Bonnar were presenting themselves as having Australia's largest range of reel
and rotary mowers.

It is clear that Scott Bonnar wanted a healthy slice of the emerging petrol-
powered rotary lawnmower market, and the new engine was fitted to the new 18"
Model 31 Spincut in 1958.



TO BE CONTINUED ...

PART TWO - MANUAL
Acknowledgement: Historian and photographer Geoff Nowak has generously scanned
an original Operating Manual for the 201. Note that this manual does not cover
the key ancillaries for carburetion and ignition. The recoil starter seems to
be of Scott Bonnar make, but the Trip-Release Impulse is of Tecumseh origin.


SOURCE: GEOFF NOWAK ALBUMS

PART THREE - Carburetion
The Scott Bonnar 201 Engine relied upon overseas manufacture of ancillaries
for carburetion and ignition. It would appear that the carburettor was an
English Amal Type 361/27.

PART FOUR - IGNITION
This has been extensively discussed in these forums.

The early engines were fitted with conventional magnetos.
At some point - probably about 1962 - Scott Bonnar adopted the then new
Wipac Magister system.

Member Willingworker has identified the sequence as this:-
Scott Bonnar's 155cc 2 stroke Model 201/202 had 3 different magnetos fitted.
Up to engine number 201-4001..............Wico magneto [Pic 1 in attached]
From 201-4002 to 201- 6193.................Wipac magneto [Pic 2 in attached]
From 6194 onwards................................Wipac Magister magneto [Pic 3 in attached]

"From this it shows that over 6000 engines were produced before the Magister
was introduced. Old S-B employees remember that they had trouble with the Magister.
It does seem strange that some engines without a Magister have a hole drilled in the
aluminium shroud. This information comes from a late 1960s Spare Parts List."

PART FIVE - IGNITION - Magister
Special mention should be made of the Magister ignition system, because it
has attracted considerable dialogue on these great forums.

The 201 had a conventional flywheel magneto for about four seasons before
the Wipac Magister system was introduced.

If one remembers that the 210 production numbers were quite small it may be
that the more expensive Magister units were a selling point to help justify
the increased costs in producing the 201. The ad below (for a Model 35)
appeared in September, 1962, and it appears to introduce this revolutionary
system.





https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/33551

PART SIX - Styling
The 201 went through two significant cosmetic changes.
The first engines, used on the Model 31 and the first Model 35s had a
squarish fuel tank. In about late 1960 the new style (with round fuel tank)
appeared on a revised Model 35. In my view, the older design looked the more
modern. The round tank design, to me, looks decidedly late-1950s Victa.

Model 31 - with 'square tank':-


Model 35 with 'square tank':-


Model 35 with the 'round tank':-

MODEL 31 with original 201 Style:-


MODEL 35 with original style:-


MODEL 35 with revised style & Magister ignition:-

PART SEVEN - Model 43
The Scott Bonnar engine was used in horizontal shaft configuration.
The almost forgotten Model 43 was a 20" version of the smaller Model 33.

Introduced in about 1960, it would have the revised cowling.