I have the twin Hitachi SU set up on an A14 with GX head. I recently cleaned out the carbs, and have been trying to tune them. I balanced them using the tube in the ear method which seemed to work fine, but setting the mixture was a different story.

I've read two methods for setting the twin SU mixture. One I read off a link from the 1200 wiki, and one that I read from the Haynes Weber/SU carb manual. The wiki link says to push the lifter pin in all the way quickly and listen to the rpms, but Haynes says to push it in only 1/32" after slack has been taken up. A lean carb will cause the engine to die, a rich carb will cause the rpm to rise and the a correct mixture will cause the rpms to rise slightly, then fall slightly. I'm not sure if it really makes a difference if you follow the wiki link method or the haynes manual method; I tried both.

Anyways, when I got the rpm to rise slightly and fall slightly when either of the lifter pins were pushed in, the engine idled poorly. One thing I remember about tuning carbs is that as you adjust the mixture and you approach correct, the rpms should rise. So this confused me. Do I trust the lifter pins or the rpms?

This probably isnt the kind of help uou are looking for, but from experience tuning carbies using the various methods you find in books and online is problematic cos unless you have 10 years experience you will always struggle. I got a cheap AFR meter kit ($65 aud) and o2 sensor in the exhaust & havn't looked back. They aren't super accurate but a damn site better than sniffing exhausts and the old 'two turns in on the idle, oncrease the main by one size, and see if it getts a flat spot at 2550 rpm on transition from 1/4 throttle to 5/8 throttle..... and if it does then check the float level' All that gear has you running around in circles for weeks.