Throttle valve modification

An application of additional shnyure port in OS 25LA cylinder brought several changes in combustion state, inviting powerful rotation 12,100 rpm with Graupner 9-5 prop under K&B 500 fuel taking along vigorous vibration, but is within tolerance. Apparent improvement of combustion efficiency was observed. In order to eliminate 3 dimensional vibration adequately, several trial experiments should be performed utilizing mechanical vibration tachometer gazing at trembling directions though the method might be so primitive now a days, re-balancing of the counter weight is performed like this even in the manufacturer's research and developing division.
Some lean mixture at idle speed of 25LA on the testing bench reminds me of the very important advice 30 years ago done by the former representative of Yamada Industrial Company at Inuyama City in Aichi Pref, the lower throat of the drum type throttle valve should be slightly opened because of lean mixture compared with the condition of natural aspiration carburetor, YS regulator controls only at middle speed and the slow speed mixture should be established promptly. In another words, very accurate and perfect balance of the drum throats upper and lower throat comparison could eliminate complicated mixture control and adjusting at idle speed in the carburetor construction. Careful checking on this important point, the fact was revealed that all of the genuine YS motors has throttle valves so designed as he had said to me.
Though I do not know he is now alive or not, hope I he is still now in our world, because we have a lot of fond memories. Now, the company has been finished the change of generations, his sun is inheriting the company.
Anyway, the bench test of modified carburetor in 25LA would be performed fairly after such modification on the throttle valves, I'm sure that the experiment would obtain favorable result.
By the way, the main needle valve for natural aspiration design makes it difficult to control and adjust precisely, dull angled needle shape makes it too sensitive and too keen to adjust it in NA fuel supply condition, only one click changes the mixture ratio effusively, but it is not impossible, within my tolerance at all.
Once obsessed by the attractive interests and curiosity of the internal combustion motors, it is very difficult for me to withdrawal from it.