How does the spring rate influence the a/f ratio?

It doesn't

Fuel mixture is controlled by needle, jets, pilot screw and float heights.

The spring rate controls how quick the slide will rise in relation to pressure change caused by opening the throttle.

With FCR or any type of carb where you control the slide not a butterfly you can overfuel the motor by opening the throttle too quickly at low rpm.

CV carbs are idiot proof, even if you crack the throttle at low RPM the slides cant just rise up due to the springs.

If your used to the controlability of FCR carbs then CVs can seem slow.

I guess that if your spring rate is too soft then if you crack the throttle at lower rpms the slides will rise too quickly and bog the motor down until the rpm picks up.

What is the force acting against the spring, the same force that determines the final slide position? Is it the difference in pressure between the atmosphere and the intake?

Neosophist wrote:It doesn't

Fuel mixture is controlled by needle, jets, pilot screw and float heights.

The spring rate controls how quick the slide will rise in relation to pressure change caused by opening the throttle.

With FCR or any type of carb where you control the slide not a butterfly you can overfuel the motor by opening the throttle too quickly at low rpm.

CV carbs are idiot proof, even if you crack the throttle at low RPM the slides cant just rise up due to the springs.

If your used to the controlability of FCR carbs then CVs can seem slow.

I guess that if your spring rate is too soft then if you crack the throttle at lower rpms the slides will rise too quickly and bog the motor down until the rpm picks up.