settting air/fuel mixture - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 2 (permalink) Old 08-06-2017, 08:34 PM Thread Starter
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settting air/fuel mixture

Been reading on the forum that most people adjust the air/fuel screws (jets?) 2-1/2 to 3 turns out from the seat. Is there a procedure that specifies max or min vacuum to achieve the optimum setting? I can’t find anything about it in the service manual. Still trying to get my “new to me ‘04” dialed in. Bike runs fine. Trying to improve the fuel economy. But…………..I don’t want to fix it if it’s not broken.

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post #2 of 2 (permalink) Old 08-06-2017, 10:54 PM
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Using a vacuum gauge, you can adjust for the highest vacuum reading, just substitute rpm for vacuum below.

You can also set them for the fastest idle rpm.

Fully warmed engine, ridden to full operating temp.

Turn the screw in until it stops (don't tighten), turn it out two turns. Do both carbs.

Start engine, add 1/4 turns out (pause in between) until the rpm drops slightly, turn back in 1/4 turn (rpm should rise slightly). Do both carbs.

Readjust idle speed as needed via adjustment knob.

This used to be called 'lean roll' or 'lean best idle'.

You can recheck the adjustment by:

Turn screw in 1/4 turns until the rpm slows or stumbles, back out 1/4 turn.
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Last edited by Spockster; 08-06-2017 at 10:57 PM.
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