Weber carburetor balancing

[FreeLSD]

I understand you. Thanks a lot!

[1,6 HF]

Quote:

Originally Posted by Alfacliff if you synch the carbs at a rpm above the idle circuits, the bleed screws have no effect. then adjust the bleed screws for ballance at idle speed. the bleed screws are supposed to affect the idle circuit only. if the throttle synch is off and is compensated for with the bleed screws, then speeds above idle wont be very synched. cliff

[FreeLSD]

I think cliff meant that running off-idle gives the real difference in airflow, not affected by idle circuits itself, along with air bypass screws. So for best off-idle running (progression and main) it worth synchronizing throttles just above idle (say, on progression), where the sync is really important - and only then eliminate any difference in airflow on idle with air bypass screws. That means that in one carbs BOTH the air bypass may be turned out to equate to another carb. Do I get it right, cliff?

[1,6 HF]

I discussed this issue this weekend, and the consensus is that it can indeed make sense to synch the carbs on the main circuit (min 300 rpm--probably about 3500), in which case there's really no point in synching on the idle circuit.

On the main circuit, there shouldn't be much difference between the two barrels of each barb. If there are significant differences between the barrels of one carb, there no 'bypass' option other than drilling small holes in a throttle plate (an option I don't really find appealing). But if there really is a difference, there may be other issues, such a worn throttle plates, bent shafts, &c.

[figleaf11]

Have you checked throttle plate positions by checking visually thru the 3 holes?
Ralph

[whagan]

Chiming in here to notice that poster is talking about using a Mercury column vacuum gauge to adjust carb idle jets, I wish, I have the gauge for my motorcycle but was disappointed to find out there is only one vacum point on the intake manifold of my 67 Duetto and that's for#1 cylinder for the hose to the Crankcase vent. Which makes no sense to me, basically a big air leak to only #1. I always adjusted throttle plates, (butterflies, chokes) first so they are equal then the idle jets (bleed screws) by sound/ rpm and effect of grounding each plug and make sure all effect RPM the same.