Have a stage 2 with mikuni. Keep my idle around 1250. Screw is around 1.75 turns out but I have messed with it too see if I can get the smoking to stop but to no avail. Dont know exactly what pilot jet I am running right now. But have you guys ever seen a mikuni black smoke on idle from a pilot jet being too big ? Just wondering where I should go from here. Not white smoking or anything. Just a rich black smoke. Smoking like this from idle to around 1/4 throttle.

When did that issue start? Has it ever been unsmoky at idle? What size pilot is in there? How long did it sit without running? Checked all o-rings in the carb to make sure none are mangled, dry rotted, etc? Replace them even if they look ok. Compression test? Intake gaskets ok and valve lash set? Leakdown test show anything?

Those are the things i would focus on. After changing the fuel in the tank.

#CFFITR
#mudmotor>physics

Engine sat up for about 3 months, bought it from a guy like this and he said it was turned rich for hunting seaosn, which doesn't make since too me cause we dont have a cold hunting seaosn down here at all. Engine has like 65hrs on it. Always smoked like that since I bought it.
Changed gas to fresh gas, made no difference.
Compression test 181-182 on both cylinders
Leakdown test 6 percent on cylinder 1, 7 percent on clyinder 2
Pulling the carb apart in a few too see what jets are in it

More I'm thinking about, leading me too a very rich tuned engine.

Vavle lash set too .006 thousands, and has brand new intake gaskets and intake to black death intake gasket.

Yeah, see what that pilot is and check the o-rings. Since it stops blowing smoke past 1/4 throttle, whatever it is is on the idle circuit. But even at 27.5 my engine never gets smoky if the screw is adjusted somewhat close to where it needs to be.

#CFFITR
#mudmotor>physics

It's got a 25 pilot. And a 167.5. Needle clip is set in the middle slot. All seems normal. All the seals and everything are good. I'm confused onto why it's running so rich now.

Plug with 20 hours maybe.

No real oil residue, mainly carbon and fuel.

There is a tiny air hole inside the flange that the air filter adapter goes on. Its the air bleed to the pilot. When plugged u get a full rich pilot. Also some heads with certain valvejobs on the exhaust seat can require as little as a 15 pilot

Another common problem is a failed fuel pump that leaks fuel into vacuum signal line. Worth a look

Abously worth a look, I will go take a look at that now, thankyou !

Not the fuel pump or the air bleed, I'm highly leaning on a rich pilot

I would stick a 17 in it just for testing. At 2 to 3 turns out it should idle kinda shitty from being too lean. This would let u know that u have found the problem area. Also it’s possible that your 25 got drilled too big in the past.

Also once i had an old mikuni fighting me with a similar situation and turned out the choke circut was bleeding fuel in the carb body. Luckily i had a spare mikuni sittin here that made testing easy

Yea I'll order a couple pilots, and hum didnt even think about that, I'll jack my buddy's tomorow and see if that straightens it also