On an exit ramp someone was wavering behind me so I downshifted and then up shifted quickly as they drifted away. The engine stopped running and I coasted to a stop.

I've checked the fuses behind the headlight and they were all good. I had just filled it with gas and checked the oil. I'm hauling it to a place where I can work on it with real tools and other people who have motorcycles.

It cranks but does not start. All the lights and blinkers work.

Later this afternoon I'll take off the seat and tank and check the wiring.

Any advice as I go along would be greatly appreciated.

Welcome. Have you checked to be sure the kill switch is in the run position?

yea that kill switch got me one time.. didn't have the heart to tell buddy who rounded up trailer to haul bike home.. if that isn't the problem..
lights, starter, charging system is completely separate from Ignition system..

CMX450 utilizes an AC (alternating current) CDI.. 100+vac is produced by exciter coil windings that are separate from charge windings all of which are attached to stator.. that 100+vac is stored in cdi compactor until signal is received from pulse generator which puts out less than 1.0vac..
As engine Quit one can assume coils are not the problem as bike will run on one cylinder

First I would pull cdi connector off, with ignition switch ON and Stop/kill switch in run position check the Black/White circuit is NOT grounding, (stop switch when On grounds this circuit as does ignition switch when Off) preventing cdi from firing..

That leaves CDI, Exciter Coil, Pulse generator along with associated connections to focus on..
First I would disconnect and reconnect pulse and exciter connections after they exit left side case..
that should scrape oxide off that may be causing open electrical circuit, do the same with CDI connector..
if that doesn't solve the problem oem Shop specs call for resistance test of exciter and pulse generator windings.. Exciter coil @ 68°F 50-250 ohms,,, Pulse generator @ 68°F 50-170 ohms
if within specs replacement of cdi is recommended.

Since the bikes production a more precise method of exciter and pulse coil testing has been adopted by Honda.
that being DVA Peak Voltage adapter for use with most volt/ohm meters..
https://www.amazon.com/dp/B0093U3TFG
current specs for the Rebel cmx250 peak voltage testing is 100+vac minimum from exciter coils and 0.7+vac minimum from pulse coil.. doubt 450 is much different with output voltage

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