View Full Version : Putting Brass Allen Caps on Carb Air Mixture Screws

05-13-2011, 09:17 PM
The head of the Air Mixture screws are ~.195" wide and they don't weigh much.

I have bought some 4-40 brass allen head screws with a head diameter slightly smaller diameter.

Since the parts are so small, I am not thinking of brazing - I'm thinking of siler soldering.

I have a micro torch that can get up to 2K F. and of course won't be using all of that, but I am thinking that I should use hard silver solder.

I also have a soldering station that will go as high as 850 F.

Am I on the right track here?



05-13-2011, 10:53 PM
You are on the right track. Probably a good bet is to go to a hobby store that has supplies for silverwork, you would be able to get everything there.

Alternatively look for 'braze 450'

Lucas-Milhaupt BRAZE 450 Silver Based Cadmium Free Filler Metal (http://www.matweb.com/search/datasheettext.aspx?matguid=f98ca465d39d4162b704cf63d5743a81)

If you have not done this type of low temperature brazing before you should practice on something other than your carburettor parts. It is very easy to overheat the metal and get a badly oxidised surface that the braze 450 will not flow on. You need a soft flame and you need to keep it moving while you are bringing the parts up to temperature. Another thing to watch out for is getting the flux on areas that you do not want to braze, especially threads. When the braze 450 melts it flows almost like water and if the flux has flowed down onto a thread the brazing material will follow it and fill up the roots of the thread.

greg b
06-29-2011, 08:23 AM
Hi im not sure this will help or not but I remove frozen brass screws from carbs on a fairly regular basis with several different methods, have you thought of putting an extention on the end of the screw and putting a pin through it so you can turn it with out a driver if you have room,in any case it may be a good idea to put the base of the screw into a alloy heat sink so you wont destort the thread and needle before you braze or silversolder it.Regards Greg.