the spark does look a little weak in the vid, should be more blue than the yellow-ish it is....
check all connections, clean with brake clean if dirty, check black wire ground
@ coil for good clean connection to bare frame.
unscrew plug boot, replace is the best option to rule it out, most any auto store should have the screw on NGK boots for around $5.
cut 1/2" from wire end before screwing new boot on.
do the ignition troubleshooting to find any problems with the coil and stator
you can turn the airscrew in to 1 turn or even 1/2 turn out to richen the pilot circut, nothing wrong with that at all.
if under a 1/2 turn produces highest idle, that suggest you need a leaner pilot jet, which in a stock carb is very unlikely.
turn the airscrew 1/2 turns or less at a time, allow 20+ seconds for engine to respond to the new air/fuel mixture, until you find the spot that produce the highest idle, this should be done with the idle speed set slightly higher than normal. return rpm's to normal after finding airscrew setting that produces highest idle.
fine tune with 1/8th turns till it revs clean and returns to idle without hanging.
no tuning can be done successfully until it is proven leak proof, with a proper leakdown tester
