Yup I know this is solved but I thought I'd post up a little more FYI:
Rotaries: Most of the early war types like the Gnome Omega, Lambda and early Monosoupape 100 were strictly controlled by switching the ignition on and off. But there were exceptions.
The early 7 cylinder LeRhone 7C, 60 hp was made with the monobloc throttling body w/fuel metering, it had two levers on it's quadrant in the cockpit, one to control air volume and one to control the fuel mixture. They were a bit fussy, as opening the air volume control also needed you to finesse the mixture carefully richer so as to not cause a lean fuel intake back firing and or popping, and possible flame out. Or too rich and the fuel mix is too much and causes a stumble and lot of misfiring.
It took a bit of experience and a good ear to run a Lerhone. The LeRhone company used their 'carburetor', for lack of a better term, for most of their common rotaries like the 9C 80 h.p. and 9J 110 h.p. engines. They could be reliably throttled to a little below half throttle but trying to reduce the throttle further would mess with the distribution of castor oil dribbled into the intake pipe. About 600~700 rpm was considered 'tickover' and was sufficient to taxi most WWI scouts with.
The Clergets were entirely different and had a more modern linked air and fuel volume carburetor and fine metering adjustments for altitude. The Clerget 110 through 130 were used on a few different Sopwith scouts including the Strutter, Triplane and early Camel, and was considered a pretty decent engine, and was more easily throttled than the LeRhone. The Bentley BR1 was a copy of the Clerget 130 with better breathing and cam timing. It was nominally about 160 h.p., both types could be throttle down to about 35%, about 400~500 RPM.
There's a few differing opinions about the Gnome copied Oberusals, whether their having a primitive throttle or just couping it with ignition. The LeRhone copied Ur.II was throttled and supposedly was better than the LeRhone. Seimen Halske counter rotating engines were able to idle fairly slow. Of course Germany's problem was sourcing Castor oil, and was a big issue during the later part of 1918 for their rotaries. There were bounties for undamaged Entente rotary engines and boxes and barrels of Castor oil.
Not to make this a mini novella edition, but.. You know Greybeard is a member here, and should anyone need some detailed assistance with WWI engine facts and figures, he's the best.