912 ULS carb sync procedure
I’m about to do my first 912 ULS carb sync and the standard process doesn’t make sense to me. After you set the starting point for the idle stops (1½ turns off of fully closed throttle) you adjust the cables for equal manifold pressure at idle. But when that’s done you have to go back and adjust the idle stop screws to contact the throttle arm(s), since the cable adjustment(s) probably moved the throttle(s) off the stop screw(s). That readjustment could destroy your throttle sync at idle.
Why not do the following? Loosen the throttle arm cable clamp bolts so the cables can slide through them, and temporarily move the return springs to hold the throttles against the stops. Then adjust the stop screws for equal manifold pressures at the desired idle speed. Once that's set, tension the cables and re-tighten the cable clamp bolts, and return the springs to their normal pulling direction. Then move the cable adjuster so the throttles come off the stops at the same time, as indicated by the manifold pressures tracking together as you move the throttle control. You should only need to adjust one cable--the one whose manifold pressure stays higher than the other as the throttle opens.
