Sorry Cape forgot about the light TT said it best If you need to know use the custom search bar on the top left. This is what I found. Thanks TT.
Ken
TwoTired:
The slides or" throttle valves" have cutaways that should face the air filter side. The cutaways have the motto "we never close". It is the engine side of the slides that really govern how much air gets through the carb.
I've alway felt that bench syncing the carbs is only good for coarse synching. Because just tightening the adjuster lock down can make a inch or two of vacuum change at idle for the guages. This can be the difference between a smooth idle...or not.
Also, worn slides can leak air that bench syncing can't compensate for.
So, on the bench in the garage, I use the "Light" method. This way I can't nick the slides or bores with very hard and sharp drill bits. And, I don't like leaving signs that I have been "in there". I shine a strong light into the carb bore at the air filter/ cutaway side. While looking straight through the carb bore, I then use the big idle knob to close a slide until the light goes out. Then I back it off until I can just see a crack of light. Now I use the individual adjusters for each of the remaining carbs to do the same, no light/light, to each in turn without moving the main idle knob. When you are done, though, the main idle knob position should be the same for light or no light for any carb slide across the bank. I then give the idle knob a twist or two to open the slide enough so the engine will start up. Then put them back on the bike and make any final synch adjustments with the guages. It's usually pretty close with low time carbs and close fitting slides. But, worn slides or carb banks that were assembled from parts of other banks, often need greater tweaking on the guages.
I'll let someone else post a drill bit method.
Cheers,
