Join Date: Oct 2006
Location: Green Bay, Wisconsin, USA
Make: GL1500 SE
To me it sounds like an ignition issue. Remember that the voltage required to fire a spak plug is much higher when the engine is loaded. Is the bike even worse if you lug it and try to accelerate? I wonder about resistor caps on the plug wires or a bad coil etc.
When the engine RPM gets up a bit and the load on the engine decreases the voltage required to fire the plug drops. If any part of the ignition system is just marginal it could run OK when the load on the engine is moderate or light but balk when the loads are heavier like when it pulls hard at low RPM.
A scope would be the best way to see if that is the issue. A backyard mechanic can hook a timing light to one plug wire at a time and have a passenger watch the light flash to see if the light flashes irregularity is in sync with the engine. You would have to do it 6 times. Once on each plug wire. Is the problem worse when riding 2 up? I would think it would if the ignition is the issue, but maybe not in lower gears.
Worked on the "big rigs" for 45 years now just riding my Wing whenever I can. Gets cold in Wisconsin.