BS38 1979 Carburetor Stumble - Low Speed

[glennpm]

Okay, my '79 XS650F is running very well now.

Two up on the pilots = 32.5
one up on the mains = 137.5
needle clips raised one step to slot #2 (lowering the needle)
mix screws about 2.0 turns out.

This is my motor info:

Uni pods
277 re-phase
no base gasket (cam re-indexed)
Port & Polish
Norton commando Specialties mufflers

Hope just minor tweaks to follow

 

[glennpm]

Duplicate post

 

[5twins]

So what cured it? Careful re-adjustment of the floats? By the way, one up on the mains would be a 137.5 for the '78-'79 carbs. A 142.5 is 3 up.

 

[glennpm]

Yes, appears the main running issue was from the floats not being set quite right and not the same side to side, i.e. tweaked a bit in one of the bowls. After this and with the 30.0 pilots, it still wasn't running great. After changing to the 32.5 pilots, readjusting the needles and re-syncing the carbs it is running very good.

As you mentioned 5Twins, these carbs are very finicky about float heights.

Thanks for the help!