Historically Speaking - The 1925 Invincible JAP


The Invincible Jap was one of Australia's larger manufacturer's of motorcycles using proprietary components (Motors, Gear Box, Seat, Magnetos and Carby) with the rest made and assembled in Melbourne.

Made between 1922 (actually first sold as 1923 models)  and 1925 they are one of the rarer Australian machines, yet surprisingly there are quite a few examples in collections which are tightly held.
There are many thoughts on the total production numbers made with production figures suggested of between 350 and 800 in total.
It has been suggested by a local reliable source that the company actually built the invincible in small batches and as such skipped a significant amount of numbers.
I believe that 350 would be closer to the total production quantity however we will never know. 

Rear Section of Our 1925 Invincible Jap.
Note: Harley style Messinger seat (which will be replaced with a sensible Big Ar-se saddle)
The Invincible was introduced in 1923, and sold reasonably well, however the design was not changed in any significant form and by 1925 / 26 with the Invincible Jap become aged and died a natural death. There are several reports of later Invincibles being sold up to the 1930's but these were most likely aged stock that was being run out similar to the vechile sales today.

We do know that there were several significant updates on the models to try and keep them looking modern.
These include the introduction of  26 x 3 rims in 1925 (to fit "Balloon" tyres which were a fashion item on Excelsior and Indians of the same year.)  to replace the larger 28" x 3" used earlier.

Other changes include a Best and Loyd oil pump that tided up the tank layout, rather than the Enots pump used on the earlier models.

Several Brake modifications were also made, but again the brakes were not well equipped and didn't work well. 

Nearside of the Machine, Note the similarity to Harley , Excelsior and Indian.
There are reports of New Old Stock (NOS) components being sold off up to before the second world war, and this could well be correct, but cannot be supported.
The heart of the bike is the motor, which was offered in different sizes to suit the buyers budget and use. The largest size engine fitted was the 8hp, being 85.4 x 85 mm stroke which totals 990cc. 

They also offered a sports motor of the same size, but with the larger Ricardo or KTR (R for racing) cylinders that were quite the rage for the sporting rider as Bert Le Vack was busy trialing an building go machines.
These motors are quite different, and were basically the same configuration that were fitted to the period Brough Superiors of the time, in various 2 cam and 4 cam styles.

The main components used are listed below

1.             Motor ( Jap 6 or 8 Hp)
2.             Gearbox Burman
3.             Seat Messinger
4.             Magneto (Thompson and Bennet / Lucas made  or Bosch)
5.             Carburetor (Cox Atmos or Schebler)
6.             Electrics (Optional but P & H Nominated)
7.             Frame (Local)
8.             Forks (Local)
9.             Fenders (Local)
10.           Rack (Local)
11.           Pedals, Bars, Luggage Rack (Local)
12.           Tanks (E B Brothers Local)

The Lighting was optional, and the suggested system was a P & H Generator (Similar to a Splidorf) that ran off the rear of the clutch and resulted in a cut out in the lower part of the tool box to accommodate the generator.

Like most local built machine's of the day, the sales team was not going to loose a sale if the customer wanted something else fitted.
As a result the Schebler carburetor was used on most of the Invincible Japs, due to the acceptance of these as they were also used on Harley's and Indian's.
The Cox -Atmos carburetor which is itself a interesting item actually works well, but has many levers, air/ fuel ratio's adjusters and complicated rotary throttle assembly, (not unlike a racing Schebler).
These were deemed overly complicated, and for this reason we plan to fit a Schebler DLX to our Invincible.
I will also write another article on the Cox -Atmos carby as this is piece of work, and is original to our machine.

There are published lists of Frame Numbers, and the JAP motor Nomenclature holds true for most Invincible's and this is readily available from a number of sources.

I hope this answers some of the questions !

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