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DannoXYZ · February 17th, 2020, 01:14 PM

There's two concepts involved here:

vacuum leak would occur between head and carbs since restriction of throttle generates vacuum. Leak in rubber manifolds would suck in extra air that didn't go through carbs. This leads to lean mixtures that indeed can cause difficulty starting.

pre-carb leaks wouldn't really be classified as vacuum-leak since there's no vacuum ahead of throttle-body/slide restriction. But yes, there's configuration of air-box and velocity-stack style intakes that shapes air-flow pattern before carbs. Any distruption of that flow would change air-volume going into carbs and cause difficulty starting.

Let's see how it starts 1st thing tomorrow morning.

February 17th, 2020, 01:14 PM	#4
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	There's two concepts involved here: vacuum leak would occur between head and carbs since restriction of throttle generates vacuum. Leak in rubber manifolds would suck in extra air that didn't go through carbs. This leads to lean mixtures that indeed can cause difficulty starting. pre-carb leaks wouldn't really be classified as vacuum-leak since there's no vacuum ahead of throttle-body/slide restriction. But yes, there's configuration of air-box and velocity-stack style intakes that shapes air-flow pattern before carbs. Any distruption of that flow would change air-volume going into carbs and cause difficulty starting. Let's see how it starts 1st thing tomorrow morning.