RH exhaust emitting occasional black smoke.

[Stevex]

LM2 with PHF36s with original bellmouths (stacks).
I've noticed that when warming up the engine prior to a run out, after flipping the choke off, when I blip the throttle I can see some black smoke from the right hand exhaust. Wife's also said that the exhaust also shows some black smoke when she's following me on her bike. Not there all the time, mainly when opening the throttle.
As the bike's off the road for winter I took out the plug and it was sooty black (the left plug is fine).
I've had the right carb apart and all the jets are correct bar the main which has a 145 fitted instead of a 140, but I can't see this being the overall cause.
Floats are good and the height's correct.
The only thing I can think of is the choke piston maybe letting by; the rubber seal is well indented. I'm going to replace both as a matter of course.
Have I forgotten or overlooked anything?

[Chuck in Indiana]

piston maybe

 :1:

[Antietam Classic Cycle]

Perhaps the accelerator pump (stroke) is adjusted differently on the right compared to the left?

[Stevex]

Perhaps the accelerator pump (stroke) is adjusted differently on the right compared to the left?

I thought that was a possibility too Charlie, but when I checked, they're both adjusted to the same settings.
I haven't checked how much fuel is expelled per throttle lift, but the adjusters are both wound out by the same number of turns.

[MotoG5]

On my LM1 the choke pistons and/or springs caused this issue over the years. Little black smoke and mild misfire at low rpms were the usual tip off. Usually replaced both items.

[omega1]

Mine did not puff out black smoke but one plug was consistently sooty compared to the other. Replaced needles and atomisers in both carbs which resolved the issue.

You need to check the actual fuel flow from the accelerator pumps - dont assume that same setting = same fueling

[flangeman_70]

Choke! Moto G5 has named it.
I've just had exactly the same issue of left choke just being unseated by about a gnats testical.
Those rubbers on the bottom of the plunger are only able to deform so far and last a finite lifetime.

Adam

[Chuck in Indiana]

Choke! Moto G5 has named it.
I've just had exactly the same issue of left choke just being unseated by about a gnats testical.
Those rubbers on the bottom of the plunger are only able to deform so far and last a finite lifetime.

Adam

Hey, the OP was first, I was second..  that sounds like the most likely scenario to me.
Still could be something else, though.

[flangeman_70]

Hey, the OP was first, I was second..  that sounds like the most likely scenario to me.
Still could be something else, though.

d

Right you are Chuck, I didn't read the quote properly 
Let's see where our good advice leads our fellow guzzista

Adam