1954 F.B.Mondial 200SS






 CNS - Vogelmann












Mid-80ies, I decided to acquire a single cylinder italian vintage motorcycle, most probably an Aermacchi. It wasn't to be larger than 250cc and had to be 4-stroke. I was referred to Heinz Laux, a collector specializing in Aermacchis and Ducatis. He was anxious to help in any way towards an Aermacchi, but he showed me his two F.B.Mondial 200SS, one of which he was willing to part with. He explained that, if I was really serious about having a piece of italian machine building at it very best, I should take the Mondial.
The Mondial was not in running condition in any way, but it was complete with the original italian documents showing it to have been registered in March, 1954. I later located and acquired another 1954 200SS in very bad condition as a parts bin. To my knowledge, there are at the most 5 of this model in Germany. I have seen only 4, two of which are mine.
Based on the original DOHC design from Oreste Drusiani for the 125cc GP racer which won the 1949, 50, and 51 world championships, a 125 SOHC production racer and street versions with a SOHC 175cc and pushrods with 125cc and 200cc were developed using the same crankcase/transmission assembly and barrel. only the timing side cover was changed as needed and of course heads differed, but all had the same hemi layout and hairpin valve springs. The DOHC 250 GP racer was also built until Mondial retired from racing after winning the 1957 250cc world championship with Provini.
Unlike almost any other single cylinder engine, the Drusiani design specifies a tunnel crankcase, a one-piece design with bearing plate on the left side for both crankshaft and transmission shafts. the primary drive, pinion and 13 plate clutch, are outside this sideplate. The housing has another separate sideplate with oilseal outside of which the flywheel runs in the typical italian style. The flywheel is fixed on the crankshaft taper without a key and drives the pinion, which can revolve freely on the crank, by dog clutch through an oilseal; the flywheel hub has its own rollerbearing. With the necessary spacers, the complete assembly aligns the crank in the crankase. Because of this design, the complete engine can be assembled and disassembled in the frame. Likewise, the camshaft can be changed in 10 minutes, and the entire transmission in about an hour.
On the right side, the timing side, the crankshaft runs in cage-less rollerbearings, allowing the crank to wander with the heat expansion of the casing. The gear oilpump is driven by worm gear directly off the crank and the camshaft by the the requisite 2:1 straight-cut gears. In the SOHC and DOHC versions there is a layshaft instead of the cam for the gear tower, kingshaft or timing chain; all three designs were variously used. Another layshaft drives the generator or magneto as the case may be. The kickstarter connects to this intermediate gear when present. Last versions of the 250cc GP engine drive the breaker points directly off this gear; the recess for the magneto is blocked off. It can be readily seen that all the gears are straight cut. The gear tower or chain housing of the OHC engines is set on the side cover which in any case carries the crank, cam, and layshaft bearings and the oil main from the pump to both crank and cam. Pushrod engines have "mushroom" tappets both bottom and top actuating eccentrically adjustable rockers. The pushrods themselves are aluminum. Oil feed to the head is through the barrel casting in the SOHC and pushrod versions and by separate line in the DOHC, but very often as in my engine, a separate line was added to the simpler engines because the seals between head and Barrel were very touchy. In the same picture, the original Dellorto 27SSF with size II separate floatbowl can also be seen. The 32mm header and long megaphone are original.
The frame is the standard type of closed double tube, brazed with lugs. There is an additional stiffening tube between the steering head and the rear frame which is bolted in after the engine has been mounted. This tube can just be seen under the tank in the side view. The very substantial hydraulic front fork has 35mm staunchions that would be comparable to a 50mm fork by today's standards. The steering head has the usual friction steering damper. Tires are stipulated at 2,50/19 front and 2.75/19 back, both on 1.6" rims. I have 2.50/19 in front and 3.00/19 in back at the moment. The bike weighs in at 110kg with 5ltrs. in the tank.
This is the world championship machine for 1957