Carb info. explination.

[gibvel]

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]

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]

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]

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]

I would think the placement of the jug makes a difference also. The fronts will run cooler than the rears......

[BigBoyinMS]

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.