How does spark plug gap effect longterm fuel trims?

[ledzz1]

Hey guys
Recently installed new plugs

The only difference being the gap was opened up a tiny bit as requested by the tuner

My question is.. my ltft for the last year has been around -10 to -12
Never seeing under that

Within a day its now reading -4

This is better however how do spark plug gaps effect ltft?
How does a tiny bit bigger gap make it run leaner in a sense even though still rich.. but more optimal than before?

Trying to understand how it effects things

 

[XR650R]

The gap is what your tuner recommends.
Spark plug gap affects everything going on in the engine, obviously.
It's specific to the tune, and a reputable tuner will have it running great with the gap they specify.
I gapped new plugs per my tuner's specs, and I'm really happy with how it runs. It's not stressed at all, just quicker.

 

[Dialcaliper]

Too large a gap will result in misfires where the coil voltage is not strong enough to cross the gap in a high pressure environment

Too small will result in a shorter lower voltage spark, which means it takes infinitesimally longer for the fuel charge to ignite and burn, giving slightly later effective ignition timing.

Later ignition timing in a rich mixture can mean slower and thus cooler combustion than intended by the tune, which means more of the fuel remains unburned and passing out the exhaust, where the O2 sensor picks up a too-rich mixture, and adjusts the fuel trim leaner to compensate.

Basically your tuner sets optimal ignition timing with a certain gap, which you want to match.