The Thunder Tiger carb has a couple issues, (no throttle stop and won't run without muffler pressure). I hear the fix is to just replace it with a Perry. Not wanting to spend $40.00 on a carb for an airplane that might get flown 5 or 6 times a year I started thinking about what could done to the stock carb to over come it's deficiencies.

First was the throttle stop.. A piece of 5/8 round aluminum stock, a 2-56 screw and spring was all that was needed to solve the first issue. Made an aluminum washer that fit over the shoulder machined into the barrel behind the throttle lever. It's 0.06" thick which is just enough to capture it when the lever is bolted down. Turning in the screw will stop the barrel from moving into the body and effectively becomes a throttle stop.

To address the second item I removed the spray bar (needle housing) and determined what size drill was needed to miss the internal threads. Chucked the housing in my lathe and drilled the needle seat in about 1/8 inch. The needle housing has a couple holes for the fuel to get into the carb and I just went far enough to be able to see the tip of the drill through the holes. I then deburred and cleaned it to be sure all the chips were removed.

The theory is that by moving the needle seat in, the needle should need to be screwed in further to achieve the same mixture as before. Hoping this will solve the problem of the needle being almost all the way out of the threads to get a good setting.

Hoping to be able to put the engine on the test stand today to see if it all works.. Really see no reason it work like a charm..

Hi Chuck, have discovered exactly what you are telling me, I just put a fitting in a piece of aluminum and bolted it in a muffler lug. Worked great but the problem is in profile carrier no pressure of any kind is allowed other than pointing the tank vent into the air stream. I really don't want to choke down the intake as I'm going to need everything that little TT can do with an almost 500 sq/in airplane. The only option is to make the fuel feed less restrictave.

Have heard some are getting by with just backing the needle almost all the way out and putting a piece of fuel line over it to keep it in place. Hoping my solution will work and be more robust than depending on a piece of tubing to support the needle. Hoping I can get it on the test stand this afternoon to see if it will work or not.

At first I wasn't really worried about complying with the rules as it started out just to be a fun venture only flying it locally. Even though I know the airplane won't be competitive I may take it to Brodaks just for grins and it will need to meet the rules.

Hey Bob, if you go to Brodak with it, have your three views and documentation, then fly profile scale. 

Bob, I got mine (a .46) to work by making an insert for the carb out of a piece of brass tubing that just fit inside the opening in the barrel. It only took one sleeve. Only work was to drill a hole for ;the spray bar.

I found on my BTRs that about .210 was the largerst diameter I could use on plain suction.  Larger just seems to need pressure of some sort.

Ended up getting a Perry carb donated by a friend then found one on eBay for a steal that was the exact carb Perry lists for the TT. I gave the TT carb to a fellow club member to tinker with. Once I had the Perry's I quit messing with it.

What you are saying might work but I almost fried one TT trying to get a stock carb to even run on the test stand without pressure. Trying to get a needle setting that work from idle to full boat would be pretty tough.