I haven’t spent much time fine-tuning the jetting with the stock airbox, but the few tests I’ve conducted have been very promising. I’m using FP needles and slightly larger main jets. The main issue with the stock jetting is that the mixture runs lean during transient inputs, particularly during quick WOT (wide-open throttle) applications. This causes a lean condition, making the engine feel gutless and low on power.
Recommended Starting Point:
Main jets: 158 / 162
FP needle: 2nd notch with a thin washer underneath
Pilot jets: 45
ACV air jet: 100 (this is in reality, the pilot air jet)
Increased float height: 4mm or 4.5mm (unfortunately, this depends on wear in the non-replaceable emulsion tubes)
This jetting setup has been tested on ADV bikes with the stock paper filter and airbox (with one Sommer door). Low-end throttle response is excellent, on par with FCRs, but there’s still a lean surge when quickly opening the throttle in the midrange, which I haven’t fully resolved yet.
Overall, this setup should feel significantly improved compared to the factory jetting.
