Ok, I'm stumped and at a standstill.
Once the sidecar was installed I never got the performance I needed (highway speeds) so off with the sidecar, back to 18T primary sprocket, new chain and short megaphone silencer.
However, even without the car the C5 still will not exceed 50mph. Period. It's fine at Start and has decent accel up through 4th gear, but once I'm in 5th I constantly have to accelerate just to keep it at 50mph. At WOT it just stutters.
What I've checked so far, and the results:
Fuel - Weak, badly leaking pump replaced. Checked for leaks in the Filter/Throttle body manifold, Throttle/Injector body Insulator, Injector body/Intake port insulator, and Injector/Injector body. No leaks noted. No performance improvement.
Injector - Has very nice spray when using the start switch. I didn't check at various throttle openings. Should I do this? Or can I assume a consistent spray throughout the throttle range?
Insulator - Replaced due to crumbling causing interference with the spray. No improvement other than the bike now starts and idles great.
Spark - Nice enough spark. Swapped between the BPR6EIX and BPR6ES. No difference in performance. Re-installed the EIX. Replaced the cap, coil, and wire. Spark even better, but no performance improvement. Plug(s) looks normal. Maybe very slightly lean without the EJK.
Sensors/Connectors - Cleaned and re-connected the all connectors at the TPS (still in original position, wasn't moved), Head Temp sensor, Fuel pump Connecter, Coil, the re-installed O2 sensor, alternator, and RR. No performance improvement.
It's been suggested I check the compression (requires removal of the Auto De-Comp), but since I'm not seeing any smoking at the exhaust I'm not sure that's justified. Please correct me if I'm wrong.
Per the Troubleshooting in the back of the service manual, the following have been checked:Tire Inflation good, Chain Adjustment correct, Brakes not binding, Cooling Fins clean, correct spark and plug, clean new Filter Element, Mobil 1 V-Twin oil as always and correct level, Wheel Bearings not sticking, Throttle cables lubed/not stickingand adjusted properly, B-Start cable not sticking, no suction leakage, and the piston/cylinder don't appear to have much carbon build-up and what I can see of the valves looks good.
I'm leaning toward a fuel issue of some kind, but TBH I'm stumped and frustrated as I'd like to get this running as good as before so I can sell it to make more room in the garage.
Any suggestions will be most appreciated.