Did you increase the number of turns on your mixture screws in the end or not?
I've just been playing around with a few spare VC engines/carbs in my garage, and one setup provided similar results as to your video.
This is a list of what I've done to solve the hesitation on my bike...
Remove all spark plugs, give them a really good clean with a brass wire brush, then hold them under a blue flame for a bit to burn off the remaining carbon deposits. As Squishy stated above, also clean out the caps and check to see which cylinders are running by tapping the downpipes. (Do this before carrying out the work we're listing). Put your battery on charge and leave it there for a good few hours.
Drain the float bowls, and remove the carbs. Get them on a clean work bench and remove the top hats, making sure not to loose the spring behind it, or the little rubber o-ring. Ensure the diaphragms are not torn/damaged. Tip the carb upside down and remove the slider pin. The pin should have one white plastic spacer underneath the clip and one orange coloured thinner one on top, between the clip and the spring. Next remove the float bowl, and check the float mechanisms aren't seized. Remove each jet in turn to check it's not blocked. Once you're happy that everything is there and in order, put it back together, taking care to seat the diaphragms correctly and remember the little o-rings.
While the carbs are on the bench, this would be the perfect time to set the mixture levels. Carefully wind the screws in and then turn them 2.5 turns out. (Yes this is quite a way out when compared to the stock figure, but bare in mind it was originally run a tad lean, and if you have any exhaust system/high flow air filter fitted this will cause it to lean out, and cause the problem you are facing). Place the carbs on top of the engine and wire in the throttle and choke cables. They are one huge PITA to fit if the carbs are already in position.
Refit the carbs and sparkplugs after letting the cylinders air for a few hours (without the spark plugs in). Refit the airbox (preferably with a standard air filter, but the K&N will do I suppose), check the wiring is set up correctly.
If one or more of the downpipes was completely cold after trying to run the bike, then leave that spark plug out of the engine (but plugged into the coil wire), rest it on the rocker cover making sure it has a good ground, and turn the bike over. (This is without any fuel in the system). If it's sparking then all would seem good, if not then try to get a better ground. If it's still not sparking then it looks like you may have a coil pack/HT lead failure.
Refit the tank, and put a few litres of fresh fuel in it. Don't forget about the vacuum pipe.
Switch the tank to reserve, and hit the starter button. If everything went well, you should now have one running bandit. If the bike is still a bit hesitant at idle, then increase the idle mixture screws half a turn at a time. Once it starts to get better reduce this figure to 1/4 turns. Remember all carbs must be at the same setting. Don't set the screws too far out, (more than about 4 turns) otherwise you will end up sooting up the spark plugs, and you'll have this issue all over again.
The next step to a smooth idle will be a carb balance.
Sorry for the very long post, but I thought I may as well document everything I did in one go.
All the best, and good luck,
Bullet5.
Topic: Bandit 400vm (1991) low rev hesitation with video. (Read 5007 times)