This is an update to my problem with my 3W-140 B2F posted a few weeks ago. Thanks to all of those for there help, but I don't think I fixed the problem yet.

Here's the current situation:
At less than 2.5 turns on the low needle, the engine will not rapidly transition from idle to full throttle without quitting lean. It does run good at 2.5 turns on both needles. This setting should be way too rich, but it's not. A few flights ago the engine ran fine at 1-3/4 turns on both needles. Just for fun, I attempted to find the point where it was too rich. There is no change in performance from 2.5 turns to 5 turns on both needles. This tells me that something other than the needle valves are limiting the fuel flow. It performs the same with the cowl on or off. I have not flown the plane, and do not plan to fly it until I can get it to run at normal needle settings.

I have done the following:
Replaced the diaphragm.
Sealed all the surfaces between the carb and engine.
Opened the restricted exhaust to the stock muffler configuration.
Changed the Ams Oil 100-1 mix from 90:1 to 50:1.
Checked the screen filter inside the carb.
Checked the fuel system for air leaks.
Isolated the static pressure port by routing it into the fuselage.

Does anyone have any other suggestions before I replace the carburetor?

Thanks Cliff

Try another carb before you take an unnecesary risk. In our attempts to conquer the problem, we sometimes lose sight of our objectives. Not a criticism, but sort of a "I learned the hard way"
type of statement_bob

You mentioned you changed the oil mix ratio of 100:1 Ammsoil from 90:1 to 50:1. Is this the same oil or the 50:1 oil... There is a BIG difference...

You mentioned you sealed the phenolic block, did you check to if it was warped? If so how? Most users have a habit of over tightening this component, leading to an air leak...

Where should I buy the replacement carburetor? Is there an upgrade to the current Walbro WGA-7?

Mike,

I may have over tightened the parts, but I also put gasket sealer between all the surfaces. I am very confident that the assembly is sealed. I did mix the Ams Oil 100-1 at 50:1. There was no change in performance from the 90:1 mix. I have used the 100-1 mixed at 90:1 in my G-62 for years. I also ran the 3W-140 on this mix for over 30 flights with no problems. I just don't think the carb is letting enough fuel into the engine.

Thanks for the help,
Cliff

Cliff

You MUST verify that the phenolic block is not warped... As I mentioned the next culprit is OVER-tightening the assembly. You don't need any additional sealer if the block is true on both sides and the gaskets are in good condition. Carbs rarely fail, but that does not mean that isn't your problem. Eliminate without doubt the pheniloc block before yo spend money on a carb.

You need more fuel because air is being sucked into the intake tract under the carb, it is no longer metered and requires additional fuel to be introduced to compensate, thus the 2-1/2 turns rich, ME thinks....

I have a friend with a 3W-140 in a 40% 3W Extra. He had the same problems you are having. He jumped through all the hoops just like you and even rebuilt the original carb. It seemed better the first flight after the rebuild, then the same old thing. Then he replaced the carb with a new one. Just like magic the problems went away. It was a long hard fought journey that turned out to be a simple fix. BTW, the dead stick landings became second nature to him. Fortunately I have had very good experience with all my 3W motors and hope it continues. I don't remember the cost of the carb. If possible you might try to borrow one just to see if it cures the problem.