Lean or rich, stumble, sooty exhaust? (Solved(hopefully))

[GreenSwede]

I´m thinking - my 75 2002 with Weber 32/36 seems to run quite fine. At the end of breaking it in, and a bit more aggressive on the throttle=)

But, it might be running a bit rich, I think. Yesterday it was running fine, but later yesterday evening the weather got moist and foggy and then the car started to stumble on throttle. My thinking is that moist air has less oxygen in it, and therefor the mixture gets to rich. Am I right?

If so, I guess I´m running a bit on the rich side.

Will read a bit and have a look at the plugs on top of a steep hill, but I think I´ll buy an a/f-ratio meter..

[c.d.iesel]

it's the opposite:

cool - cold wet needs RICHER

warmer - hot lower humidity needs LEANER mixture

time to remove the ski rack ?

[GreenSwede]

it's the opposite:

cool - cold wet needs RICHER

warmer - hot lower humidity needs LEANER mixture

time to remove the ski rack ?

Ok, but not so cold, but wet, then? (8 degrees celsius, that is..(google) 46 in fahrenheit)

Hot air expands, right? Containing the same amount of oxygen?

So a certain volume of cold air contains more oxygen than the same volume of warm air. Disregarding humidity.

But, if temperature is the same and only humidity changes? Damp, moist air - doesn´t it contain lesser oxygen, the mixture resulting richer due to the lesser amount of oxygen in the same amount of air?

[landon]

Water vapor is less dense than air. I've always wondered why people say fog is great for motors. The air is less dense and has less oxygen. So why is water injection good? Seems to me that cold dry air would be best.

[allbim]

Is the manifold heat hooked up and working?

[GreenSwede]

No, actually it isn´t. Bought the Weber as a kit many years ago, and the lower part with the hose connections didn´t fit the new manifold. So it´s passed by.

Is that the difference that would make? Seems a bit logic that I could have some of the mixture condensate in the manifold. Should I dig out a stock intake and hog out for the weber..? Darn.

[allbim]

No, actually it isn´t. Bought the Weber as a kit many years ago, and the lower part with the hose connections didn´t fit the new manifold. So it´s passed by.

Is that the difference that would make? Seems a bit logic that I could have some of the mixture condensate in the manifold. Should I dig out a stock intake and hog out for the weber..? Darn.

Without manifold heat you will (for sure) get carburetor icing under certain conditions. I have actually seen frost forming on the mounting flange of my 32/36 on a warm day before I heated the manifold.

It really runs better with the heat on, and I’ll bet the gas mileage is better too.

[GreenSwede]

No, actually it isn´t. Bought the Weber as a kit many years ago, and the lower part with the hose connections didn´t fit the new manifold. So it´s passed by.

Is that the difference that would make? Seems a bit logic that I could have some of the mixture condensate in the manifold. Should I dig out a stock intake and hog out for the weber..? Darn.

Without manifold heat you will (for sure) get carburetor icing under certain conditions. I have actually seen frost forming on the mounting flange of my 32/36 on a warm day before I heated the manifold.

It really runs better with the heat on, and I’ll bet the gas mileage is better too.

I guess I´ll have to find the old one and modify it to fit the Weber, to exclude that from what it might be.

Same thing today, no fog but a bit of rain this morning. About 10-12 degrees celsius.

If I am at about 2500-3000 revs and slowly press down the accelerator it´s fine, but if I smack it down faster it stumbles. A lot, like I either cut fuel supply, or I poured a bucket down the carb. Also, took it for quite an inspired run just now, but the exhaust is still sooty black at the end. I reckon it should`ve burned clean. Therefor I´m guessing rich. Or ignition not going along..

BTW, my jetting is:

(I intended to follow CD´s prescription, but must have ordered or received the wrong ones, I guess. CD´s in the brackets.)

Primary

idle 60 (60)

main 140 (140)

air corr 160 (145)

Secondary

idle 55 (55)

main 160 (175)

air corr 175 (175)

secondary enrichment plugged

Do I get to much air on primary? And too little juice on secondary?

And, the idle mixture screw, while running best on idle is just a tad more than one turn out. That´s too little due do the small air correction on primary?

I´ll see what jets I have laying around.

Oh, and I´m on 191 ft =)

[c.d.iesel]

a side note - the coolent hoses attached to the intake manifold provide

hot engine coolent to heat the intake manifold - Good thing.

did you by-pass the coolent hoses ?

black sooty is overly RICH! for sure

something is causing excess raw gas

flow to cause that.... ? jets not secured

Aux Mixing cross tubes in wrong position

at the top of the throats?installed up side down?

Aux tubes fitting loose?

got any photos of inside the carb and surrounding

area - we might SEE sumding ?

[GreenSwede]

Here´s a few, just removed the filter top now. I´ll lift the lid and get better ones tonight.

[GreenSwede]

And the primary..

[GreenSwede]

a side note - the coolent hoses attached to the intake manifold provide

hot engine coolent to heat the intake manifold - Good thing.

did you by-pass the coolent hoses ?

black sooty is overly RICH! for sure

something is causing excess raw gas

flow to cause that.... ? jets not secured

Aux Mixing cross tubes in wrong position

at the top of the throats?installed up side down?

Aux tubes fitting loose?

got any photos of inside the carb and surrounding

area - we might SEE sumding ?

I bypassed the bottom that was on the stock intake manifold with hoses. And I´ll match the stock one to the Weber instead. Any day now.

And, didn´t I say I thought it was to rich..?=)

[GreenSwede]

Might have an issue here..

[GreenSwede]

Better pics. Why would the seal break like that?

[c.d.iesel]

YIKES! Ola -

i was just about to say " look at the carb base"

mounting after looking at your photos and then I

see you already found IT!

try installing the 2002 carb insulator block with paper gaskets.

Provides a better seal, heat isolation, soome vibration

dampning. Look for the bmw part number

in the 'parts book'. The carb never does well without a

bmw fiber-block or after-market rubber insulator block.

Pierce Manifolds Calif.

SPACER BLOCK 7mm

No. 99005.119

....and double check that those AUX VENTURI's are tight.

if the ends fit loosly and they are able to wiggle any

in their slots the motor will run snotty!