Ok,tried it all, balsa box, trumpet both facing rearward and forward, no trumpet, leaning needles untill poor performance low end and high end. I have a Quique yak 102" cannister mufflers does the standard bad things. Runs great on the ground, sluggish on takeoff untill turned skyward runs great throughout rightside up and knife edge but turn this baby inverted near 1/2 throttle and starts to loose rpm. Don't move the throttle and roll right side up and goes back to running perfectly. What gives with this engine. BTW I have the new style trumpet with the insert to reduce the opening. Any ideas??????

how much fuel have you run through it?

Mine done the same thing untill it was starting to run in then it was a matter of lean up the top end a touch fly then land and do it again untill it run perfect no stack on.
Open whole near the carb. 98oct fuel 100-1 amsoil.
The low needle needed an 1/8 turn richer.
It is a matter of getting them balanced i found the low needle on the thilsone carb will efect the top end asswell.
I spent a whole day on this to get it good again after trying the velocity stack once fitted and re-tuned I lost 400rpm but had more grunt down low but sacrificed my uplines going vertical. removed it LOL

They are fidely to get right but once you get it you will love it instant responce heaps of power no gurgling inverted

The problem is called Tillotsen. When it goes awy so will the problem. There's just no nice fuzzy way to say it other than directly.

What you are experiencing has been a frequent and long standing issue with the Tillotsen carbs. Some people never encounter it, others can't get away from it. Those that have made the change to another carb have always been pleased they did. The other issue with the Tillotsens is that it's not a "one time" adjustment carburator. More often than not, the carb will need to be adjusted for every flight. At least that's been my experience with a whole lot of 3W engines using a Tillotsen.

My gurgling-when-at-fast-idle-and-inverted problem went away after I leaned the High end a little. this was on a 3W 100 with Tillotson carb.

Anybody know the replacement carb number in a walbro?

SDC-80

Safe Flying!

thanks

To anybody else having 3W 106 tuning issues:

I have two of these engines swinging 27x10 and 28x10 props at sea level. The one runs with cans and the other with pits style mufflers. I have to say it has been an absolute nightmare to get these things dialed in. The primary problem I had was as follows: Easy start, solid good idle, quick response when going to full throttle and perfect running at full throttle. So in theory its good..... High end and low end wise. The problem was that when you start to run and only open to half throttle, it bogs down, but eventually gets going. Then in flight, when really bad it would run and sound as if it is missing. When you go inverted it virtually dies on you.

To make a very long story short....contrary to what I know (small 1/8 changes to low end needle) I went nearly half a turn leaner on the low end needle. What a difference! Now it runs great. What I found was a good indicator of where to go with the low speed needle was to move the throttle quickly to about half throttle. Doing this it would hesitate and spool up much slower than expected. This means go leaner on that low end needle.

Hope this helps somebody.

I have a 3W55 US Competition Version 9side carb) and have this problem. Im going to try your solution. I think I have it dialed in on the ground but when I taxi out and accelerate it bogs in the mid range badly and seems to go rich inverted.

TOM,already solved the problem,back in 06,it's the Tillotsen carb.i had these carbs before they are a pain in the butt,Walbro is much better.

I thought I read somewhere that the Tillotson was better at mid range mixture control than the Walbro. The article said that the Walbro was designed for uses that were either at idle or wide open like chain saws. Not sure where I read that.

Over the last two days I tried leaning the low end. Seemed to get better. Today I had a hesitation ond richened the low end lightly and leaned the high end. Had a perfect flight and was happy. Then on the next flight I had the flat spot at around 25% throttle. High end and idle were great. what the heck! Could I be dealing with an ignition issue instead?

My engine is a 55i Us edition. It probably has 40 flights on it and has either been very rich on takeoff and when inverted or had a hesitation at 1/4 throttle. Very frustrating.

Sounds like you are getting close. These carbs are sensitive to adjustments, a 1/16 turn makes a difference.

Don't want to hijack this thread so see "3w inconsistent"