Italië / Italy

 


CAPRIOLO CENTO 50 149 cc (ohv)
The Cento 50 respect to the competitors is comfortable, elegant but expensive and delicate. It was produced in a few hundred exemplary from 1953 to 1956.

The Cento 50 (by Riccardo Orioli)

In November of 1953, at Milan Show is presented the model Cento 50 aesthetcally quite with frame structuraly identical to Capriolo 75 but with plentiful dimension, Earles fork, hidraulic suspension, have four stroke flat twin engine ( two opposite horizontal cilinders of 75 cc), equipped with 2 Weber carburettors. Even if it is schematicaly similat to BMW, represents a new in the Italian production. The purpose of the Aero Caproni was to build cleanly, smart superior bike respect to comperitors of same cylinder capacity.

The Frame

Made in Arco di Trento factory have the same structure of the 75 for to underline the continuity of the species. The prototype have the front fork more sophisticated respect to Capriolo 75. Of original costruction, with pressed steel sheet arm it is Earles type but will replaced with a plus traditional telescopic type just before to go in production. The rear fork arm still remain in pressed steel sheet with two idraulic bumpers mouted in inclined position. Refined it is also the care of the particulars how the use of directional indicators embeded in the rear optical group or the warning light of neutral position included on headlight. Comfortable also the single seater seddle and the little carrier. In the 1955 will born a second series of the bike and at this time, besides other improvment, will insert the full width brake hubs.

The Engine

Apparently obtained from the union of two termal groups of 75cc put in a new basament with integral four speed gear box, result instead different from progenitor whose keeps only the architecture. In fact the major part of the pieces aren't interchangeable and the generous monobloc seem calculated for to ospitate more bigger cylinders. This will do not much lubrification problem ( emulsion with condensation water ) so to conduce to replace the two axes crank shaft with two solid counterweight ( second engine version ) for to reduce the empity space. The ignition with two coils is battery-coil ignition type with automatic spark advance ( centrifuge mass ) post inside a large frontal case. This position will not favour the reliability of the bike that is vulnerable in the ignition. So for to put remedy the igition contact was moved from battery coil ignition cap to classic igniton contact inside flywheel. At the same time the ignition coil was reduced from two to one. Only one carburettor is present for to give the mixture at both cilinders. This solutions seem derived from automobilistic technique instead of calssic BMW implementation with one carburettor for each cilinder. Although tried, the difficult to syncronized two carburettors have carry to this solution, only concession is a air regulation screw for each (long) aspiration pipe. The distribution keep the face cam put in the lower point of the head in manner to favour the lubrification. The two cams are specular and only the left cam is the same to 75. Differently from Capriolo 75, the gearbox have the same longitudinal orientation like crank shaft, but the final trasmission drive use a chain inside a shaft so to avoid one of two conic couples and its power dissipation. This choice favour also the travel comfort because the bike is deprived of classic overturn pair associated to shaft trasmission drive. Other side, vibrations, in the twin flat engine structure are absent.

Engine: flat twin four stroke . Alloy cylinders with refitted cast iron liner.
Bore and Stroke: 47mm x 43mm 
Capacity: 149,2 cc
Compression ratio : 1:7
Power: 7.5 hp at 6000 rpm.
Head: aluminium alloy with cast iron valvles seats120°.
Valvle drive: cast iron, angle of valvle 45°.
Combustion chamber: hemispherical.
Distribution: over head face cam and rockers.

Distribution diagram: 

Inlet valvle Exhaust valvle 
opens 34° BTDC opens 60° BBDC 
closes 50° ABDC closes 24° ATDC 

Generator: Nassetti or Dansi 35/38 W, 6V
Ignition: battery coil ignition Marelli 
Spark advance 32°-38° respect to BTDC
Contact breaker with gap 0.35/0.40mm
Spark plug: KGL F 70

Carburettor 1953: Weber with diffuser 18 

Carburettor years later : Dell' Orto UA18BS 3 

Throttle Slide 60 
Needle jet 255/B 
Needle D 7 fitted 2rd notch 
Main jet 72 
Slow jet 35 
Float weight 5g

Gear box: integral four speed gearbox, speed insertion realized by expantion balls, cluthc plates under oil.

Transmission: 

1st gear 2nd gear 3rd gear 4th gear* 
Gear ratio 8:1 5:1 4:1 3:1 
Speed 19.5 Km/h 31 Km/h 48 Km/h 70 Km/h 
*Note: The 4th gear is direct. The ratio 3:1 is made from the conic couple 21/42 on crankshaft and the conic couple 30/44 output to gerarbox. 

Final transmission : chain
ratio = 2.631 Pinion Z=19 Crown gear Z=50 

Lubrication: with gears pump, recovery with gravity. 
Filter: with metallic grid for aspiration and centrifugal, in output, on the crankshaft.

The literature on this bike is poor you can buy the book Italian Motorcycles of Mike Walker 
printed by Aston Publications

Ciao

Riccardo Orioli

CENTO 50 149 cc (ohv) .
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