From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Instructions for setting and testing the carburetter diaphragm, air valve, and low speed jet.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan194 | |
| Date | 29th January 1925 guessed | |
| contd :- -9- speed jet should be set only within the automatic range of the carburetter i.e. at the speed where the diaphragm is just on the point of admitting air through the diaphragm ports. Normally the diaphragm is set so that the top face is .025 above the bottom of the ports in the high speed choke and a test for this setting is given later. Therefore the air valve should have a very slight lift approximately .050" when this adjustment is made otherwise we run the risk of setting the mx{John H Maddocks - Chief Proving Officer} jet too soon before dilution starts and thereby encountering a rich spot. To test the diaphragm adjustment, run the engine at such a speed that the air valve has just seated with a correct mixture. By unscrewing the complete dash-pot, we shall reach a point where the running becomes erratic. The amount we have to unscrew to obtain this state should not exceed one turn. The mechanical setting of the low speed jet is taken as approx. 40 mins. from full down position. Of course the best setting for each individual carburetter, which must be found by experiment, will probably vary slightly from the above figure but no excessive variation should occur as this should indicate some other trouble - possibly in the induction system. The mixture should be tested at the point where the air valve ports start to open by observing the position of the mixture control which gives the steadiest running. If it should be exceedingly rich at this position - assuming that the high speed jet is correctly adjusted - the fault will most probably lie in the spring having too much contd :- | ||