Just my opinion, but stop wasting start spray shyte, that 'trick' is rarely effective, but keep at it if you want to kill extra time. Give the engine a proper leak down test to detect vacuum leaks.
If I had that bike I would give is a going through and check a number of issues that you might have overlooked during overhaul and modification.
Carb - SHA15:15 did you put a oring between the carb and 15mm intake. 11/16 X 13/16 X 1/16 oring will suit the 15mm SHA. Make sure you derestrict the intake if it necks down from 15mm where it transitions from round to rectangle. You would need jet in the 74-78 range when you decide to put a goodly pipe on that instead of the stock pipe.
Exhause - is it stock exhause completely and no derestricted? The higher volume of air-fuel being processed bu the bike needs to breathe, derestrict the pipe or get a good aftermarket one on there. Stock exit should be opened to about 11mm ID (not bigger) for the kit and carb. Use a new crush gasket and tight her right tight, first time you get the engine heat soaked check it is still right tight while the engine is still cooking hot.
Timing - for stock points set the points to 0,40mm (.016 inch) at index, timing should be 1,5mm BTDC. Plugs should be gap at 0,40mm.
Kit install - did you index the kit to the motor or just throw on a thicker base gasket? Index the kit by putting the piston at BDC and check that the edge of the piston aligns with the floor of the exhause, Use gasket material of proper thickness to make that alignment happen. For the ring gap, if you have no kit manufacture spec it is 0,004 per 1,00 of bore, you need that to be correct, it is only coincidental if it is correct with a new assembly, they are not pre-gapped from the manufacturer.
Clutch is not hooking up in that video. On the clutch, the inner arms are for starting and the pads on the periphery of the cover are the main clutch. First make sure the starter arms extend fully to the outer bell without effort with their little springs unhooked. Even if its starting action seems to be acceptable. Make sure the friction surfaces inside the cover and inside the carrier are free of surface rust, you can scrub them goodly with 220 aluminium oxide cloth. If the main pads are not squared then they may be worn too much, so if the tips of the friction material is worn down you would want to change them out, or change the entire cover. Treats sells the main clutch pads, there are two sizes of rivets used in Moby main clutches, 3mm and 4mm. Dont know what size this set comes with but you will need those drill bits to drill out the original pad's rivets anyway.
https://www.treatland.tv/motobecane-stock-clutch-PAD-n-RIVET-set-p/mbk-clutch-pads-n-rivets.htm Treats also sells the cover as an assembly https://www.treatland.tv/motobecane-stock-clutch-drum-p/mbk-clutch-drum.htm but you need to wire weld the cover to the core before using it because they are not very well assembled from the factory.
Hope some of that helps.