Hi all, I've been doing carbs sync and I've adjusted them almost the same but at the time I was synchronizing every pair the idle speed was raising initially from 1250 to finally around 2800 rpm. Haynes says that measures must be 230 mmHg with a maximum difference of 10 mmHg.
Tried to solve it screwing out the idle screw but idle does not drop from 2800 rpm. In this photo you can see the idle adjustment screw that is already separated from the part that it pushes when it's screwed in.
Checked the intake rubber tubes as I saw some crack in them, they were in very poor condition. That could explain the high idle speed because of the extra air intake due to the cracks. Changed them but sadly the idle speed problem remains the same.
Checked that in both open and close position the throttle cable opens and closes the butterflies completely.
I suppose that after changing the intake rubber tubes a new sync must be done but I wonder if the vacuum from the first carb must be covered. Normally it is connected to the gas tank petcock but when doing the sync it was connected to anything. Maybe some air was entering through it and distorted the sync measure.
Green arrow is where I attached the Carbtune and red arrow is the vacuum intake.
Something to say is that idle speed was 1250 rpm both in cold and hot conditions (never used the choke to start the engine) so it could indicate that something is wrong with the fuel/air mixture. The idle screw was always completely turned out, no effect due to it.
I checked the turns of the mixture screws, they had all 2,75 turns out except carb 4 that had 3,25 turns out. I adjusted all to 2,5 turns out but idle speed remains the same.
Final questions:
Could the vacuum intake in carb 1 affect when doing the sync?
Should I do a sync again covering it this time?
Could a lean/rich mixture affect to the idle speed knowing that before the sync the idle speed was correct?
Idle speed raises after carb sync
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gallegoenlaluna
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Last edited by gallegoenlaluna on Tue Feb 19, 2019 8:55 pm, edited 1 time in total.