So why did I do this, when my Kawasaki KLR-650 has never darkened the interior of a dealer's door? Well, it's the stone age vs. the digital age. My KLR-650 is defiantly stone-age. It has one cylinder. The ignition has its own coil at the magneto and does not need the battery in any way to operate. It has a stone-age carburetor that is gravity-fed with no pumps or anything involved, as long as the bike is upright enough that the carb is below the gas petcock, the carb gets gas. If you kill the battery somehow, no problem -- just push-start the thing. The downside of course is that it makes about as much power as a riding lawn mower (34hp in actual dyno tests), has a top speed similar to a Ford Pinto, and gets fairly humdrum gas mileage for a 650cc motorcycle (around 40mpg).
But my new DL650 V-Strom is digital age all the way. You can't look up at the clocks and read off the odometer mileage when the bike is off. That's digital. You gotta turn the key on. You have a digital fuel gauge, digital temperature gauge, digital Antilock Braking System. The fuel pump is inside the gas tank and requires up to 40 watts of power to operate, and drives digital fuel injectors on digitally controlled throttle bodies. If you have no battery power you aren't going anywhere -- the injectors won't run, the fuel pump won't run, the stepper motors controlling the idle valves won't run, you're SOL. The upside is that you get 60 horsepower, a smooth power curve from idle to redline thanks to the oxygen sensor allowing the fuel injection to precisely map the fuel-air ratio at all throttle settings and RPM's, clean emissions thanks to the catalytic converter in the tailpipe, and even if you ride it fairly aggressively you still get 50mpg, and can get better if you keep your RPM's below 5,000 RPM (but that's boring!).
Now, for the most part I don't mind the fact that my Nightstrom is completely digital age. The upside is that it has tremendous power, excellent ridability, and gets great gas mileage. But one of the things required at 600 miles for a DL650 V-Strom in California is a throttle valve sync. And because idle is computer-controlled on the Nightstrom, this requires Suzuki's special computer to disable the computer-controlled idle and center the idle stepper motors on that computer-controlled throttle body. Then, and only then, can you adjust the idle air bypass screws so that a) each throttle body has equal vacuum and b) the bike is idling at the specified 1300 rpm when the idle stepper motors are centered. Anything else would be Just Wrong(tm).
See, here's the deal. Idle speed is controlled by the computer on this bike. There is a flap in each throttle body that allows more or less air to pass into the throttle body at idle. This flap is controlled by the idle stepper motor. When the bike is cold, the idle stepper motor will adjust the idle slightly upward at the same time that the injection system enrichens the mixture slightly. When you are at high altitude, again the idle stepper motor will adjust to give you slightly more air while the injectors lean out the mixture slightly (remember, we have an oxygen sensor down by the catalytic converter, so the injection system always knows how much fuel to inject to get ideal combustion).
So anyhow, under normal conditions, you want the idle stepper to be in the middle, so that it can open or close the idle air flaps as needed when conditions are *not* normal. Thus the need to use the special Suzuki computer to lock the idle stepper in the middle. If you try to adjust the idle air bypass screws without first locking the idle stepper in the middle, the computer will notice that you're giving a little more air to cylinder A that was showing more vacuum than cylinder B, and will tick the idle stepper downward to reduce the idle back down (since giving more air raised the idle to above 1300rpm). It is easily possible to get the idle stepper into such a position that it's no longer capable of adjusting idle. You can sorta compensate by giving a little less air to B at the same time as you give a little more air to A, which hopefully would avoid clicking the stepper, and I would do that if I was in the middle of Africa and didn't have Suzuki's special computer available to me, but there's no guarantees that this will keep the idle stepper centered when the bike is idling at 1300 rpm under normal conditions. The only guarantee is to use Suzuki's computer to lock the idle steppers in the center before you start twiddling the air screws.
So anyhow, that's the downside of the digital age: trips to the dealer (or potentially to an independent mechanic who happens to have that digital tool). Sigh. Computers. Talk about your love-hate relationship... I love the benefits of the thingies, but sometimes I do pine for the days of stone-age motorcycles where you didn't need much beyond a screwdriver, a big hammer, and a pair of pliers to fix pretty much anything. Luckily I have my KLR for when I'm pining for those days :-).
-- Badtux the Motorcyclin' Penguin