I always used a friend's Unisyn flowgauge when balancing carbs. It worked fine at low RPMS and at high RPMS. IT DID THE JOB.

I am now using an STE Synchometer with absolute measurement dial but it pegs at higher RPM's. I tried the two different rubber fitting that came with the STE tool and also tried to use the holes in these fittings as bleeders but no luck.

How can this tool be used at 3000rpm?

Works fine for me at 2,500 rpm. Unisyns have been useless above 1,000 rpm for me. Make sure the radiator fan isn't blowing air into the sides of the unit and make sure you have a good seal against the carb inlet. There are also different flow versions of the Synchrometer. The SK flows up to 30 kg/h and the BK flows up to 35 kg/h. They also sell a bypass adapter that lets in a set amount of air for those engines that flow above the limits of the meter.

Thanks again John. You are spot-on.

I figured it out (silly me)... the main trick is that the meter is best viewed when rotated sideways 90 degrees . I was first trying it in vertical and 180 degree rotation but the parallax was preventing a useful measurement . I also figured out (now that I could see the scale in more detail side on) that around ~2,000rpm I could set fast idle screw so that the front carb measures exactly 25kg/hr I could then measure the rear carb and adjust the balance screw so that it matched exactly at 25kg/hr.

It was very easy to balance at off-idle and at idle and more importantly, absolute and repeatable measurements.

I would recommend the BK version to others to tune in the higher rpm range.

Edited July 25, 201212 yr by Blue

I also noted that on these carbs, 23mm of fuel to fuel bowl top lip height is ~13 turns (1.3cm) down (max) of the jet.