Full circle crankshafts were originally intended for use in reed valve engines. Their ideal field of operation though is with motors where the carburetor is mounted directly onto the cylinder itself. The extensive development of crankshafts on the German/Austrian racing scenes recently has enabled the 40 PS milestone to be reached and even exceeded without the use of nitrous oxide. The differing crank design concepts all start with the full circle crankshaft (from MAZZUCHELLI) as its basis.
The basic idea behind the full circle crankshaft is to enable an increase in the compression of the fuel mixture before it reaches the combustion area above the piston (HPC). With crankcase reed valve motors it cannot be helped that the full circle crankshaft crank webs interrupt the gas flow within the crankcase rather abruptly. The use of a cylinder where the carburettor is directly mounted onto it, such as the QUATTRINI 177cc1XL, release the true potential of a HPC crankshaft design. This combination allows higher engine revs and extra power.
The MAZZUCHELLI crankshafts are produced using tough and wear resistant materials, have minimal machining tolerances and very low bearing play. High revolutions and a long life are therefore guaranteed. If your needs are not satisfied with this crankshaft you may want to take the LPC route (flowed or bell shaped crankwebs)
Conclusion: Recommendable for the QUATTRINI 177cc cylinder. Top choice for reed valve engines.
Full circle crankshaft / stroke 57-60 mm / connecting rod 105-110 mm/ 24/25, M12
Full circle crankshaft, 95 mm crankweb (flywheel side), ø 97.9 mm crankweb (disc valve side), balanced at 12 o'clock, lower connecting rod bearing = silver bearing, 105 mm connecting rod (125/150 cc) or 110 mm connecting rod (200 cc), 57/60 mm stroke, oil seal housing 24 mm, bearing housing 25 mm, stump cone with M12 thread, incl. connecting rod bearing.
SIP-TIP: New bearings, oil seals, woodruff keys, nuts and washers for the flywheel and the clutch are a must. Adequate crankshaft tooling #27338000, #21071000 and #18119000 is a big help. Direct intake cylinders such as the QUATTRINI 177cc are the ideal basis. MMW or MBD reed valve manifolds are also a possibility.