MALOSSI small frame tuning – the next generation! Close on the heels of the 136cc MK II cylinders release the Italians follow it up with the MALOSSI Hyper Racing (MHR) version of their smallframe mainstay. An aluminium cylinder, new barrel-mounted inlet manifold, bridged exhaust port, new piston equipped with just one piston ring and monster transfer ports you could lose things in! This version is MALOSSIs ticket to the premier direction of smallframe racing - Hyper Racing.
Similar to previous versions, this cylinder is compatible with all Vespa 50-125/PK50-125 models, with both conventional disc-valve or reed valve inlet manifold systems. To enable this a suitable inlet cover is included with the kit. To make use of the cylinder mounted reed-valve intake the manifold from the MK II cylinder can also be used. The mounting studs are identically spaced, although the cylinder itself will require slight modifications below the first cooling fin. Otherwise MALOSSI also produces suitable manifold for the 136cc MHR cylinder. The right angle at which the petals were positioned, in relation to the cylinder, has been changed to a slight angle. This allows a much improved gas flow (fluid dynamics) of the fuel charge mix.
Alongside the massively increased size of the transfer ports the port timings and inlet port angle have also been redesigned on the MK II version. The most noticeable novelty in the area of the exhaust outlet is the new bridged port design. The inlet port is divided into two stabilising the single-ringed piston in this area.
CONCLUSION: All in all an viably attractive cylinder kit with lots of tuning potential MALOSSI rate this cylinder with a power output of 25 PS at 11.000rpm. We, however, see this as a minimum figure with enormous room for a much increased power output with careful tuning. The overall quality of the materials used in its construction guarantee durability under heavy load.
Aluminium 57,5mm bore/6 transfer ports
Aluminium cylinder with a hard chrome lining, 51mm stroke, 6 transfer ports, reinforced piston with a single 1x1mm right angled piston ring, M6 sized exhaust studs, bridged inlet port, double bridged exhaust port, centralised cylinder head with an o-ring gasket and 12.5:1 compression, kit includes a gasket set and cylinder inlet cover.
SIP-TIP: The potential of this kit deserves its combination with a larger carburettor kit, new spark plug, racing crankshaft with a 20/20 or 24/24mm cone-stub dimensioning, performance exhaust, an electronic ignition system and a taller gearing (2.86-max.2.34). Take care to mount the piston ring with the lettering towards the pistons roof/crown. The increased size of the transfer ports requires the OE crank case to be modified, especially in the stator-plate mounting area. Our SIP standard crank cases also require this modification. All necessary instructions are included in the delivery.