Whilst setting up the CO on my standard st2 I was able to obtain arange of 0.9% to 2.4% approx (Thats min to max value) Is this OK. I ask because on the FIM website they talk of settings in the 4% to 6% range as ideal. Can I assume this is only obtainable when a Ultimap chip has been fitted ? The bike seems to run fine on a 2% setting where I left it.
?? You can go over 10% usually, if you want to. There are two ways of controlling the CO. The trimmer in the ecu itself is a global adjustment. It alters both cylinders. You then need to tweak the air bypass screws to bring both cylinders in together. These are the two you closed when balancing the throttles. Screwing them out will weaken the relative cylinder, screwing them in richens. A good start to get both the cylinders the same is 1/4 out on the front and 3/4 on the rear. The rear always runs a little richer, although less so with the FIM eproms. Get the front to 4% or so with minimal bypass using the trimmer and then pull the rear down with the bypass screw as required.
Thanks Nelly, The school of thought I have followed was to balance the throttle bodies with Vacuum gauges (This should in theory give equal CO in both cylinders) then set the overall CO on the trim pot. I seem to have acheived a good balance thru the revs on the butterfly linkage alone (i.e. both air bleeds shut). I might check this again in case the Gunsons CO I bought is not working correctly
You have to balance the throttle bodies mechanically with both air bypasses closed, else the mechanical balance of the butterflies will be distorted by the air being bled in down stream of them. Once that's done, then balance the CO as above. One other thing to bear in mind is measure the CO at the take offs on the down pipes. The exhausts are linked at the collector so measuring at each can will again distort the readings. It can be done but you need to monitor changes in CO pretty quickly as your measuring the average of both pots. The gunson will not react quickly enough. The sampling pump isn't big enough. The theory on correct CO being achieved just by balancing the throttles is a sound one, but in practice won't ring true. The rear cylinder is running hotter and the inlet tract not as vertical as the front one. Those two elements affect the combustion as well as others, so the rear will run richer on "identical" settings, hence the bleed screws to balance things up. Even on near identical CO readings, the corrected values for CO, O2, CO2 and lambda usually differ between cylinders. If the highest CO reading you can get is 2.4%, somethings not quite somewhere would be my guess.
Linear Mode
