1951 F.B. Mondial 125 Bialbero
What we have here is a gem! In original and unrestored condition this is one of the three factory F.B. Mondial 125 Bialbero (DOHC) racers known to have survived. It is a 1951 model and is thought to be Carlo Ubbiali’s World Championship winning machine.
We thought it pertinent to run this feature now after the unfortunate passing this week of Ubbiali at age 90.
Let us look at some background on how F.B. Mondial and the 125 Bialbero came into existence.
Count Massimo Boselli was a wealthy land owner and lawyer from Ancarano who had four sons and a daughter. The youngest son, Giuseppe, not only had good management skills he also raced motorcycles and became a partner in GD [Story on GD at this Link], racing them as well. He then went on to be involved with CM (Story on CM at this Link). It was during his time with these two companies that became friends with engineer Oreste Drusiani who manufactured engines and parts for both firms.
In 1929 Giuseppe and his brothers founded a company F.B. (Fratelli Boselli – Bosselli Brothers) to produce three-wheeled delivery vehicles. The concern was set up in factory space owned by Drusiani and proved to be quite successful until it was destroyed during WW II.
The company re-established itself in 1946, continuing to produce three-wheelers, then in early 1948 Giuseppe bought a prototype motorcycle engine designed by Oreste Drusiani’s son Alfonso. This motor was very radical for the period, a 125 cc four-stroke single with DOHC.
Nearly all small displacement race motors were two-strokes at the time. Unusually the design featured a “monobloc” crankcase – this was cast as a single piece (similar to a tube with open sides), it was not split into either vertical or horizontal halves. Alfonso was hired to run a newly established race department and resulting bike was called the F.B. Mondial.
The new bike first raced in September 1948 but had to retire with a split fuel tank (taken from a Moto Guzzi). However the next month the bike, ridden by Giovanni Cavanna in extremely bad weather, set 125 cc world records in the standing start kilometre and mile. On October 24th F.B. Mondial won their first race with Nello Pagani victorious at the Monza GP.
Thus began a period of total domination of the 125 cc class in the new Grand Prix World Championships that began in 1949. F.B. Mondials won every race in ’49, ’50 and ’51 – with riders Nello Pagani, Bruno Ruffo and Carlo Ubbiali respectively.
The main rivals MV Agusta and Moto Morini had fielded two-stroke powered machinery in ’49 but had to switch to four-strokes thereafter in an effort to be competitive.
Ubbiali’s victory in the 1951 125cc class was followed by eight more world championships (all on MVs), five on 125s and three on 250s.
The 125 Bialbero used a short vertical shaft with bevel gears at both ends to drive the central gear of five overhead gears of which the outermost gears drove the camshafts. All these gears were on the right hand side of the motor. Bore/stroke was 53 x 56.4 mm. A dry sump and external flywheel were employed.
My thanks to the bike’s owner, John Goldman, for the majority of the information used to put this column together.