RichG wrote:The carb syncronisation adjustment balances the lift of each throttle slide in the carb. Its very fine adjustment indeed and a vacuum gauge is needed to measure the pull through each carb.

Update to my previous comments on 'very fine adjustment':
I have just syncronised the carbs on my 21R track bike. Wow, they were a huge way out. One carb was pulling about 25% more than the other at 2000 rpm (constant). It took a few turns on the balance screw to sync them, made a huge difference to how the engine runs.

Checking float heights is also a good point. The last 2 sets of carbs I have stripped had floats way too low in the bowls (high measured float height), so low level of fuel maintained in the bowls. But more likely to impact on higher RPM fuelling than at tickover.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30