Motorcycle Questions? Ask a Mechanic.
Hi and welcome to the site, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.
Initially and on "...running in 2 cylinders only...", which 2 cylinders?
Have you carefully checked for sparks? ...on all four?
Please click HERE.
Interesting as in most instances, if 2 & 3 are cold then it would be an ignition issue; i.e. missing sparks.
However, that "...all four has sparks..." would point back to a fuel delivery/starvation issue.
Still, the description of "...started to leak..." would possibly point to a float/valve issue; either adjustment, stuck open and/or not sealing fully.
Consider replacement with a repair kit.
Between these two (2), the product HERE appears to be best suited.
On "...need to perform some adjusment..." would depend on what type of float is used;
At this point that the performance of the Honda has not been tried with all cylinders firing, need for needle replacement can not be determine. It can only be 'felt' when everything else are working as expected. Hence not yet needed......and may even be not at all needed.
That the floats are plastic would mean that these can not be adjusted. If flooding, then automatically these plastic floats would have to be replaced. To my understanding, there is no test.
With the carbs / bike running good BUT rise engine RPM seems to be slow or IF hesitancy when accelerating and/or a flat spot THEN checks / works needed on:
Spark plug burn check would help confirm.
"... vac adjuster..." please provide a clear picture or even a LINK to the product description.
There would normally be a connection port at each intake manifold or coupling covered with a rubber cap or a screw.
Connect leftmost hose (#1?) to the leftmost intake manifold as this would be cylinder 1; then 2, 3 and 4 respectively.