This version of the Max 91HZ series utilises a completely different system for supplying and regulating the the fuel supply to the carburettor and is called DRS (Demand regulator system). Unlike the Max 91HZ-PS, the Max 91HZ-R utilises a pressure bleed from the crankcase to pressurise the main fuel tank. The pressurised fuel feed is then regulated by a newly designed regulator that is well isolated from the heat of the engine through its mounting position. That regulated fuel supply is then feed into the new 61E carburettor.

The serious 3D flier now has the choice between a mechanically pressurised fuel system (Max 91HZ-PS) or the tank pressurised system in the Max 91HZ-R. It is purely a matter of personal choice for the pilot. What other manufacturer gives you that level of choice in one engine size?

Mechanically, the Max 91HZ-R is identical to the other engines in the Max 91HZ range.

Specification:

Displacement: 0.91 cu in (15 cc)
Bore: 1.091 in (27.7 mm)
Stroke: 0.976 in (24.8 mm)
Output: 3.4 ps @ 15,000 rpm
Practical rpm range: 2,000–16,000
Weight w/o muffler: 22.05 oz (625 g)

Includes: OS #8 glow plug