If the heavy negative ground wire from the battery is connected to the frame/engine block and you jump the two large terminals on the starter solenoid with a screw driver the starter motor should start running.
Of course, that assumes the heavy positive power wire is good and is connected from the battery's positive terminal to the starter solenoid.
I mention this because looks can be deceiving and both of these wires may look connected but if there is an internal break down between the wire eyelets and the actual wire it may be good enough to carry weak amounts of current but it won't carry the heavy amperage the starter motor will demand.
Many times I've seen battery cables that looked good and looked connected on automobiles but the starter wouldn't work.
On removing the cables on these cars I've found all sorts of corrosion between the terminals and the cables, or cables that had wires that were so badly corroded that they wouldn't carry any current in excess of that needed to light the headlights.
I know on our Royal Enfields we don't usually let things get that bad but still there is a chance of an internal wiring breakdown between the cable ends and the heavy wire.
I think Royal Enfield India studied and took to heart the words found in,
"The Basics of Proper Wiring and Its Application to Motor Vehicles-1947" as written by Lucas.
I've heard rumors that his chapter entitled "The Creation of Electrical Smoke" was particularly fascinating to them.