hsukaria

Here's the in-depth review of the Fox new carb by Earl, post #2697, page 108:

There doesn't appear to be any pictures of the New Fox Two Needle Carburetor out on the internet. So here are some pics of what it looks like.
It has a lot of similarities with the Bodeman Design Carbs as used on Webra engines, especially like the Webra TN carb. So they may have used it for inspiration, but I don't know. Now the hollow tube or spray bar inside the Webra TN carb extends only 1/2 the way across the bore, but the spray bar in the Fox carb extends all the way across the bore of the carb. The Fox carb barrel on the inside has a recessed hole to match the spray bar so that the barrel can close all the way. I also included the instructions on how to adjust the carb too. The carb also uses a main needle with a very gradual taper to it, so this allows for a wider range or less sensitive range of tuning. A sharper taper on the needle can make it more sensitive and harder to get a fine adjust setting. Especially with low or no nitro glow fuels. I have seen other brand engine carbs have such a narrow adjusting range that you wind up being 1 click rich and 1 click too lean.So having a wider adjustment range with the needle is pretty nice. Not having a detent means you don't have to compromise on trying to get the engine set just right where you wish you had 1/2 a click on the detent for the needle valve.

One rather esoteric feature of the new Fox carb is that you can rotate the spray bar slightly to change the mid-range transition. But you rarely need to make this adjustment. You might need to do this adjustment, if you had taken the carb apart and the spray bar was set off of pointing straight down. The hole in the spray bar (discharge port) should point straight down inside the bore of the carb. If you are having problems with the engine, you can remove the carb from the engine and check to see if the hole is pointing straight down or not and adjust it as needed. You loosen the two screws locking the spray bar/needle holder and rotate it ever so slightly to set it. It doesn't matter if you rotate the hole forward or backwards from pointing straight down. If the engine was running a little bit too rich in the mid-range and the low speed and high speed needles are set good, then you can try rotating the spray bar very slightly, in 1/64th of a inch to 1/32nd of a inch increments. So like I stated it is a small or tiny adjustment. Also this depends on the other two needles having been set good also. Many people tend to get ham fisted and go for 1/4 turn adjustments and you don't do that, just little movements and wait to see how the engine responds for a minute before you try it again. Do not make this adjustment while the engine is running though, way too dangerous. Anyway this ability to clock the spray bar is a feature that is on SuperTigre carbs and also K&B, and some others too. But if you read the instructions for Perry carbs you'll note that they state to make very tiny adjustments or rotate the idle mixture disc in very tiny increments. The K&B carb uses a eccentric off set screw head for this adjustment. Supoertigre also uses two locking screws on their carb. The Webra TN carb did not have this feature as the spray bar/needle holder was lightly pressed into the carb body, so it would be difficult to change it. I have retrofitted several engines with the new carb and also ran several new engines with the new carb and I have not had to make this adjustment.So I doubt you will need to make the adjustment. But it is a nice feature to have should you need it. Since the Fox factory tests runs all of their engines, if is extremely unlikely you'll need to ever use the adjustment. Plus the low speed needle will be set pretty close to perfect from the factory too.



























Here is another pic as posted by Badger a while back in this thread:



You can see in this pic of a Webra TN carb where the Fox design could have been derived from.