Hey guys, I've recently started club racing in the UK and I'm riding my race converted CBR600F4 that used to be my daily commuter and at the moment I am basically running it stock, excluding required changes for ACU compliance, plus a radial master cylinder and some different sprockets for gearing.

I've done 2 rounds now (Snetterton and Cadwell Park) and i have found that I am losing out down the straights quite significantly once I get into 4th and 5th so I am looking at options to increase power without significant engine works since I'm not sure I can do engine upgrades in my class, and I feel like there's simpler options to start with. I was trying to find full exhausts for this bike but there doesn't really seem to be any good options out there so I was considering getting a full system from Arrow that is actually for an F4i and using the port for the O2 sensor for an aftermarket AFR gauge to keep an eye on the fuelling as the season progresses and tweak the carbs as I go.

Question no.1: Has anyone run an aftermarket exhaust system from an F4i on an F4 before, and if so what issues should I look out for?

Question no.2: Has anyone tried to use an AFR gauge to monitor fuelling before, and if so how reliable is that?

For reference, this is the exhaust I'm looking at https://www.sportsbikeshop.co.uk/mot...tent_prod/4626 , I would get the full titanium system, and this is the kind of AFR gauge I'm considering, https://www.speedingparts.co.uk/p/en...gaAr8gEALw_wcB

N.B. I have run several different gearing configurations and I'm certain that's not the problem.

 

1. AERO: Using slightly larger windscreen improves top-end. Double-bubble can gain you 3-5kph depending upon tract

2. GEARING: are you hitting redline at max-speed down longest-straight? If not, you can gear down to increase revs and acceleration. Go up 1-2 tooth on rear-sprocket each time until you hit redline

3: POWER: most external mods give minimal gains since engines are so optumised from factory. It rules allow, run free-flow air-cleaner and remove air-box snorkel.

Yes; factory WOT tend to be too rich and you can pick up +10% hp from just leaning out mixtures to max-power 13.5:1 AFR. I gained +14% on my Ninja 250 by just fine-tuning AFR with no hardware mods!

I recommend wideband with datalogging. Much more accurate and safer than trying to stare at AFR meter while going 200kph down straight! You can also draw AFR curve with RPM similar to dyno chart for optimum tuning. I really like these units, fully digital with on-board memory for datalogging. No laptop needed: https://wbo2.com/