Round top switchover gone bad--HELP!

[justaZcarguy]

Mornin'!

Yesterday I switched from the flat-tops to a set of round...

No vac leaks, no fuel leaks. Back carb is running rich, VERY rich. We are talking Richy Rich here, the adjustment for the jets on the bottom of the carb is dialed ALL the way up and the car still runs. Idle seems smooth is the funny thing, then, if you depress the throttle about half way and hold it, you get a motor that's suddenly only reving about 800 then falling, acting like it's starving instead of climbing in RPM. This is if you depress the throttle and hold it, it just sits and stumbles like it's running out of fuel. Which there is little or no rich smoke coming out the exhaust during this, but if you just quickly depress the throttle and let it go, you get a quick rev and a lot of black smoke, like rich burn, not blue like oil smoke. I have never messed around with these carbs, this is a first for me. I have a air synchrometer and they are both balanced flow wise. There is 3 and 1 oil in the chambers (about 20wt.). The front carb seems to be operating fine. Now, I am getting this result by lifting up the pistion all the way into the dome and seeing if the engine stumbles. (Running lean, right?) it stumbles when I lift up the piston in the rear carb, but runs smooth when the front piston is all the way up. I've waited for it to begin to stumble and it won't. So, you would dial up on the bottom adjustment to lean it out, right? (on the rear carb) Well, the adjustment is dialed ALL the way up (on both carbs). And with the adjustment knobs on the bottom of the carb all the up on both, how is the engine even running? I thought the needle would be "seated" and this would cut off fuel????

Sorry to ramble on, it's early and I need some coffee.

Anyway, I also need some help...

Thanks all....

Have a nice Sunday!

With any luck I will also! :tapemouth

[Rob]

I'm not a carb guy but have you checked that the needle and seat is not leaking in the back carb? If it's leaking you will get some bizzare results not dissimmilar to what you have described.

I think you can check it by removing the float bowl top, holding the float up and running the fule pump to see if any lkeaks