Misfiring K75

[nortonbrian]

I will try to keep this brief. Purchased 1992 K75, been sitting for a year. Replaced battery and tires, rebuilt brakes, changed all fluids.New filters, plugs, gas tank clean, injectors serviced. Replaced all hoses, fuel pressure ok.
Bike ran fine for 200 miles, then developed an intermittent misfire. So swapped out following:
Control unit under saddle with a known good one.
Ignition unit from e-bay, could be bad
HES, e bay, ditto
Cleaned ground wires under tank
Cleaned all connectors, used dialectic grease
Bike starts up immediately, and when given throttle it wants to go, but the misfire holds it back.
Tried a jumper wire [fused] from the battery to the starter solenoid, also bypassed the ignition switch. Can any electrical genius suggest bypassing the wiring harness?
I wish it would quit completely, might be easier to find the problem.
My thoughts now are to replace the wiring harness.
Any suggestions gratefully received, as theres a great bike lurking in there somewhere.

[K75RT Keith]

Check the plugs to determine if one is fouled
Check the plug wire caps are tightly installed on plugs
Possible bad Plug Wires or possible failing coil. 
HES unlikely unless problem on occurs when hot. 

[Motorhobo]

+1 on spark plug wires. If you're still running the original OEMs they've seen their day and look on beemerboneyard or euromotoelctrics.com for aftermarket replacements because the OEMs cost 4x as much.