I've always assumed the co settings reflected the variances in the injectors themselves-Gen I bikes seemed to confirm this as the settings, once learned, were all over the place. The Gen II thing has troubled me-it would seem something else had come into play,
IF it was true that many bikes had the exact same settings-which doesn't really make sense to me. Yamaha most likely tunes the motor before it leaves the factory-setting the injectors to establish consistent CO readings across the 4 cylinders. Unless the cylinders themselves have wildly varied inconsistencies, the injectors would ordinarily be very close to each other in co settings. But, on the Gen I's, like mine, the settings varied from +21 to a -3-a pretty wide spread (Franks settings). So, either Gen II's have a consistently inconsistent variance (tough to wrap my lips around that statement), something else has recently (or always has?) come into play if they are setting a whole range of bikes to the same exact numbers. Which would blow my theory all to hell. As has been stated many times-the only sure way to know is to open up the individual exhaust runners and pull a CO reading from each hole. I've come close-the Holeshot header allows me to pull numbers off of pairs of cylinders-unaltered by catalytic converters, the numbers are fairly true-and with the flowed injectors, all set to the same CO reading on the display, the numbers are so closely aligned as to suggest that the CO alterations
are to adjust for discrepancies in the individual injectors. Soon after I installed them, a mis-fire developed, which I suspected was an injector gone sour after being screwed with-CO was sky high on the right side pair-but a bad plug wire connection turned out to be the culprit. Having already replaced the suspect injector (#3), a CO test showed little difference between the flowed injectors and the unflowed replacement-but it was there, however slight. Bumping number three 4 points evened up the numbers. Subsequently, the bike ran great until the motor started getting rough, and was
EXTREMELY sensitive to TBS synch. Thinking I had screwed the pooch with the whole deal, I had resigned myself to just buying 4 new injectors and being done with it, until a post by another forum member suggested a problem with the large electrical connector just under the neck, and sure enough, mine had the very same corrosion. Cleaned up, Frank runs great. I cannot stand ANY vibration from the motor, and so do a TBS synch about once a week (yes, it goes out of whack that often, nature of the beast), but as a result, Frank is almost perfectly vibe free. For those that think this is excessive, medical issues insist that I absolutely minimize right hand buzz, or I quit riding. I can synch Frank in 10 minutes, tank on to tank on, so it's not like it's intrusive-besides, I like keeping him in top form. It has suggested to me though that as sophisticated as modern fueling systems have become, the old problem of keeping 4 completely individual cylinders, each with it's own air and fuel mixing device, operating as 1 is still very much with us, not much better than 4 CV carbs, or, God save us, 4 Amals or for that matter 4 SU's.
Great for power and fine tuning, but rarely all on the same page without constant attention.
