WEAK SPARK AT PLUGS

Hard to say. If the ignition key were left on by mistake for a time and drained the battery it would result in burnt breaker points. Check for spark. Remove a spark plug cable and use one of the old plugs inserted in the cable end. Ground the plug body to the engine block and have someone try a startup, observe spark plug gap for spark. No spark, problem found. Go to breaker points. May be a weak spark(yellow color) and need to replace points and condenser anyways.

Check ignition coil.

very weak and intermittent spark on a points system indicates a failed condenser
replace it and if the spark is a bright blue--ok but if better but not good change the coil

Same way as you do on a car. You missed the spark plug wires. Look for corrosion on the rotor cap and measure the resistance of all the spark plug wires .
The high resistance ones need changing.

i ran in to a similar problem years ago , the spark plugs were bad ,old,and weak.be sure to use delco plugs that are specific to that engine

.....A weak battery comes to mind for starters. A carboned up spark plug is another; start with a new spark plug. If I recall correctly from 39 years ago, your bike has ignition points and condenser. Remove the points cover (on left end of the overhead cam), and check the points. Burned? Pitted? Get a new set of points and condenser but for now, just file the points a bit using an emery board or metal fingernail file. Set the points to .015 clearance at the high point on the cam lobe. If you have a timing light you could check the timing and adjust as needed by rotating the points base plate left or right. Bad points give resistance to the flow of electricity. When the points are closed, the condenser gets charged up. Less electricity going through the points means less of a charge going into the condenser. Now the points open up and the stored charge goes from condenser to coil. The coil then produces a spark. With a low charge in the condenser, the spark is weak and will not jump a wide gap. Set the plug gap to very little and the weak spark can jump the gap. The standard gap is .028. ....... I don't recall when Honda move the points to the flywheel but the images below may help if your bike is that style. Clean any rust on noted parts; magnets and pick up coils. Okay, now I have done my part. Now you gotta do yours; please rate my answer. Thanks!

if it has a duel points system. possible condensers , incorrect point gap, bad coils
if it has transistorized distributor it will be the ignition igniters that are bolted to the distributor
They are scarce and expensive