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Bike: 1979 GS1000L, 2 valves per cylinder, w/ 28k miles, compression 135 to 140 lbs on all cylinders.
Story: Late this past winter, the valve clearances were checked, only 1 of 8 needed any adjustment, the original points-type ignition was removed, a used electronic ignition from a later-model GS was installed, the timing was set and double checked, new plugs were installed (twice), the gas tank was flushed/etched at a radiator shop, an in-line fuel filter was installed, the carbs were pulled off the bike (twice) and were inspected, cleaned, blown out with compressed air, adjusted, and synchronized with mercury sticks. (In the process, #3 carb was found to be trashed beyond repair and was replaced with a clean, functional, used carb from another bike, the float height settings and fuel and air adjustment screw settings were found to be way off and were adjusted, the needles and seats and O-rings were inspected and found to be OK, and the whole kit and kaboodle was put back together and the bike was ridden for 200 miles by the mechanic (I told him "Pretend it's your bike and ride it around for while"), before being turned over to me.
Current Situation: Certainly, the bike is much, much better than before. However, after the 200 miles with the mechanic, and another 100 or so with me, the plug in cylinder #4 is black, and the other 3 plugs are 3 different shades running from tan-to-brown. The bike seems to "flutter" at engine speeds in the range of 2800 to 3400 RPM, which is where I seem to ride about 80% of the time. The flutter goes away above about 3500 RPM and the bike runs strong at higher RPM. Trouble is, I ride around 3000 RPM most of the time.
Any ideas what might be wrong? (I'm on good terms with the mechanic, who is puzzled too, and said he'd get it right, no hard feelings, and said although he checked the needles and they looked OK, maybe it's the needles. He also said that the rear wheel sprocket hub might have some play in it which might explain the flutter. That could be, but that doesn't explain the different spark plug colors.
Is it unreasonable for me to expect a smooth-running bike, on a bike almost 25-years old (but with "only" 28k miles), or to expect 4 cylinders/carb/spark plugs to be all all running the same, and showing the same color on all 4 plugs after a few hundred miles?
Story: Late this past winter, the valve clearances were checked, only 1 of 8 needed any adjustment, the original points-type ignition was removed, a used electronic ignition from a later-model GS was installed, the timing was set and double checked, new plugs were installed (twice), the gas tank was flushed/etched at a radiator shop, an in-line fuel filter was installed, the carbs were pulled off the bike (twice) and were inspected, cleaned, blown out with compressed air, adjusted, and synchronized with mercury sticks. (In the process, #3 carb was found to be trashed beyond repair and was replaced with a clean, functional, used carb from another bike, the float height settings and fuel and air adjustment screw settings were found to be way off and were adjusted, the needles and seats and O-rings were inspected and found to be OK, and the whole kit and kaboodle was put back together and the bike was ridden for 200 miles by the mechanic (I told him "Pretend it's your bike and ride it around for while"), before being turned over to me.
Current Situation: Certainly, the bike is much, much better than before. However, after the 200 miles with the mechanic, and another 100 or so with me, the plug in cylinder #4 is black, and the other 3 plugs are 3 different shades running from tan-to-brown. The bike seems to "flutter" at engine speeds in the range of 2800 to 3400 RPM, which is where I seem to ride about 80% of the time. The flutter goes away above about 3500 RPM and the bike runs strong at higher RPM. Trouble is, I ride around 3000 RPM most of the time.
Any ideas what might be wrong? (I'm on good terms with the mechanic, who is puzzled too, and said he'd get it right, no hard feelings, and said although he checked the needles and they looked OK, maybe it's the needles. He also said that the rear wheel sprocket hub might have some play in it which might explain the flutter. That could be, but that doesn't explain the different spark plug colors.
Is it unreasonable for me to expect a smooth-running bike, on a bike almost 25-years old (but with "only" 28k miles), or to expect 4 cylinders/carb/spark plugs to be all all running the same, and showing the same color on all 4 plugs after a few hundred miles?
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