gibvel Posted September 18, 2009 #1 Posted September 18, 2009 (edited) Okay, I downloaded the service data spec. sheet for my 99... see attached. About halfway down page 1 it gives the CO% at which the carbs are supposed to be set. It appears that carbs 1 and 3 are to be set between apporximately 2.5~3.5% and 2 and 4 are supposed to be set between 3.5~4.5%. What gives and why would that have you set them differently. Let me see if I have the cylinder placement correct also. Sitting on the bike facing forward 1=LR, 2=LF, 3=RR, 4=RF I'm sure of 1 and 2 just can't remember 3 and 4. Edited September 29, 2009 by gibvel
RandyR Posted September 18, 2009 #2 Posted September 18, 2009 I have a Guess. My guess is that the air intakes aren't perfectly balanced so the carbs have to be tweeked differently to balance things overall.
BigBoyinMS Posted September 18, 2009 #3 Posted September 18, 2009 My guess... Fuel and air have weight and on acceleration the fuel/air mixture will tend to want to go toward the rear cylinders making them slightly richer. The CO adjustment may be meant to lean the rear cylinders a bit to offset the extra f/a mixture that gets pushed in. In city riding this would make sense but on the highway you have way less acceleration forces.
gibvel Posted September 18, 2009 Author #4 Posted September 18, 2009 My guess... Fuel and air have weight and on acceleration the fuel/air mixture will tend to want to go toward the rear cylinders making them slightly richer. The CO adjustment may be meant to lean the rear cylinders a bit to offset the extra f/a mixture that gets pushed in. In city riding this would make sense but on the highway you have way less acceleration forces. Interesting!! I guess they figure most people are going to get into the throttle on these instead of being a Poko Joe, huh?
bar836 Posted September 18, 2009 #5 Posted September 18, 2009 I would think the placement of the jug makes a difference also. The fronts will run cooler than the rears......
BigBoyinMS Posted September 18, 2009 #6 Posted September 18, 2009 I would think the placement of the jug makes a difference also. The fronts will run cooler than the rears...... I thought about that but being water cooled I don't think there is much difference in temps from front to back. On my air-cooled Road Star it definitely seems to make a difference! The rear plugs on a Roadie are almost always sooty compared to the front. And there's only one carb so no adjusting for it. On mine the rear sooty plugs probably comes from the way I usually ride it. I ride it 3 miles to work and accelerate 'briskly' from a stop (or slow and turn) 14 times getting there.
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