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I have a '78 750 that either runs well or doesn't run as well. There's no inbetween, it's like a switch. The problem is electrical.
In the good state, it runs as it does from the factory, pulling hard past 5000 rpms, even in fifth. 100 mph doesn't seem like a problem (never tested).
In the weak state, it feels like a cylinder dies at full throttle. My personal speculation is that the spark is too weak to fully ignite the denser fuel-air mixture pumped into the combustion chamber at wide open throttle. The bike will struggle to 80 mph.
Idle is the same for either state.
Again, this is not a carb problem, it is electrical. I am certain of this. All four cylinders have spark. In the weak state, the spark color changes from orange to dark blue but is not fat (less than half a millimeter wide). In the good state it is probably fat.
Coils are at 4.7 ohms each.
1 and 4's coil: 42.7K ohms between wires
2 and 3's coil: 32.0K ohms between wires
Both coils get 11.7 volts with the ignition on and bike not running. Battery is new and at 12.53 volts.
Points are at .014 and 8,000 miles old, as are the condensers.
The bike still runs but not optimally. One clue is that there has been some stormy weather in the northeast since I rode the bike last. The long-gone instrument panel lights in my father's Dodge Dart suddenly came back on after this weather. The humidity is screwing around with things...
I can tell between states because in the good state, the GS throws my head back as soon as 2,000 rpm.
I miss the good state
My question is, did I miss something? I thought my timing was good, maybe I should recheck...
In the good state, it runs as it does from the factory, pulling hard past 5000 rpms, even in fifth. 100 mph doesn't seem like a problem (never tested).
In the weak state, it feels like a cylinder dies at full throttle. My personal speculation is that the spark is too weak to fully ignite the denser fuel-air mixture pumped into the combustion chamber at wide open throttle. The bike will struggle to 80 mph.
Idle is the same for either state.
Again, this is not a carb problem, it is electrical. I am certain of this. All four cylinders have spark. In the weak state, the spark color changes from orange to dark blue but is not fat (less than half a millimeter wide). In the good state it is probably fat.
Coils are at 4.7 ohms each.
1 and 4's coil: 42.7K ohms between wires
2 and 3's coil: 32.0K ohms between wires
Both coils get 11.7 volts with the ignition on and bike not running. Battery is new and at 12.53 volts.
Points are at .014 and 8,000 miles old, as are the condensers.
The bike still runs but not optimally. One clue is that there has been some stormy weather in the northeast since I rode the bike last. The long-gone instrument panel lights in my father's Dodge Dart suddenly came back on after this weather. The humidity is screwing around with things...
I can tell between states because in the good state, the GS throws my head back as soon as 2,000 rpm.
I miss the good state
My question is, did I miss something? I thought my timing was good, maybe I should recheck...
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