[ho50ca]

Bottom of the float bowl there'l be a tube-like fitting; the screws are inside. If they haven't been touched they'll be capped by some little brass plugs that'll need to be very carefully drilled out, as the screws are right behind them and you don't want to bugger them.

This is easier if you disconnect the carbs as a bank and flip them over. You'll have to remove the tank, disconnect at least the choke cable, all vac lines, fuel lines, and anything else that prevents this.

Loosen the clamps holding the carbs to the rubber manifolds and rock-pull them loose.

When you've done this, grease the manifolds with a little silicone brake grease or KY and slide the carbs back in. Reverse removal.

After this, generally you can come up with a small tool so you can make adjustments to the carbs in place with, if you look closely at how everything is arranged and what can be got in there. I use the tip of a replaceable bit screwdriver, marked on one side with white out so I can count the turns.

 

[ho50ca]

No kidding raising the needles didn't help, that's primarily for midarange enrichment. Turn out the idle mixture screws a 1/2 turn at a time and see if it improves.