New Guy Here from Knoxville
My buddy and I both have pre-owned royal stars his being a 1997 tour classic with some popping and occasional backfire on deceleration issues. His carbs had been monkeyed with previously; pilot screws, float settings and throat sync all over the spectrum. Mine is a 99 with the standard gurgling sound and slight popping while decelerating that you get with most factory tuned royal stars and has yet to be fine tuned.
Anyway, after learning what I could from you guys here at venture.org, I pulled my buddys carbs and cleaned all passages thouroughly, I set all float heights to 0.645 with calipers against base of float bowl, backed off throttle adjuster on carb #1 to close the throat and checked highest postion of throttle plate (closed) to bottom surface of throttle bore. I checked and rechecked measurement and kept getting conflicting measurements before I realized the hardend steel slide on my quality calipers would not measure the offset angle of throttle plate against the 90 degree angle of throttle bore. Remembering I had an old plastic caliper with a round pin slide I remeasured plate to bottom of bore facing with this tool and got consistent measurements every time and adjusted carb 2 exactly to carb 1, then #3, then #4. All throttle plates adjusted to 0.678. I adjusted pilot screws 2 1/4 turns out, put carbs , airbox, and tank on and... Whoops, I have a problem!
Carb #3 popping thru exhaust while throttling off and snuffing type sounds while idling when warm. Pilot screw adjustment had no effect and exhaust gas was cool compared to carb 1,2, and 4. All other carbs and cylinders sounding perfect. This indicated to me that #3 was running very rich.
After taking carbs off several times to see what the problem was and rechecking every measurement, my buddy and I devised a wooden jig to re-check float levels with clear plastic tubing with carbs fully assembled leveled and plumbed, and then mounted jig in my vice and set the carbs on top. Guess what, No 3 carb float level measured 1/8 high, while all the rest measured exactly at bottom circumference of main diaphram cover ( which is where I wanted them - high for quick low end throttle response). I took a wild guess and lowered float #3 by 0.035 and rechecked float level with plastic tube gage
and it came out exactly level with bottom of radius of diaphram bowl.
Now, can someone tell me why this one float would measure 0.035 lower than the rest but gage equally level with the other floats with tube gage?
Could it be that float seat is lower than the others? Could it be the float seat is turned in deeper in this one carb?
At any rate, we put carbs, airbox and tank back on bike and cranked her up. My God, It Sounds so Good and So In Tune - no backfire and no poping, and no snuffing, sound - Time for a little road check!
At constant throttle the bike seemed much quieter than before, but what was amazing was the smooth but powerful and instant throttle response and acceleration from closed throttle to open and every position inbetween. No lug, no lag or hesitation whatsoever. We hit a long stretch of sweepers and mild twistys where I could keep power up in third and fourth gears, while mainly using engine deceleration for braking and all we could hear, other than that wonderful throaty whumping sound, while accelerating out of curve, was a corresponding cooking sound, kind of like hot coffee percolating fast with an underlying boiling sound while decelerating into it.
And last but not least; Zero, pops, cracks, sniffles, or snuffles while riding for an hour and a half. We'll check the tuning with vacuum gage and tachometer next week but he and I agree, we'd be hard pressed to change a single thing.
