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> aluminium brazing
post Jun 18 2014, 09:28 AM
Joined: 26-Apr 13

does anybody have any tips for aluminium brazing/soldering. i have a carburetor that is worn and i would like to build it back up some how. where it is worn is probably too small and narrow to get the tig torch in. I've done plenty of brazing and soldering but never with aluminum. i bought some of the alumaloy soldering rods that they advertise on you tube but i am yet to try them out
hope this doesn't sound too much like a handyman question , i joined ukwelder for the in depth technical stuff on here
post Jun 18 2014, 09:32 PM
Joined: 20-Feb 10

Which bits are worn??
post Jun 19 2014, 04:02 AM
Joined: 26-Apr 13

its a keihin FCR carburetor. the slide has some wheels on it and the wheels have worn a groove into the body of the carb. i'm guessing the body of the carb is cast aluminium, what filler material would i use if i am able to TIG it?
David 46
post Jun 19 2014, 09:37 AM
Joined: 27-Sep 08

If it is a Spray Casting it will border on impossible to repair it. if it is a normal cast Aluminium part Alsi5 (4043) should do the job if you use Tig. If you Braze it (Solder) the filler wire will need to have 10%-13% Si I use AlSi12 you should be able to get Flux from any good supplier. Cleaning is a very important factor and mis your Flux using distilled water clean your rods with clean Stainless Steel wire wool shortly before Soldering and coat the rod with flux and the carb too.
To coat the rod pick up flux on one end hold it vitical and run the flux down the rod using the flame a very soft flame.

There are special filler rods for Spray Casting where as the flux is inside the rod, I have only seen them once and that was about 20 years ago.

I hope that is a help,

post Jun 19 2014, 11:15 AM
Joined: 26-Apr 13

thankyou david i appreciate the info. the rods i have say 4043. the alumaloy brand. i might go to the welding shop and buy an extra long tig nozzle.
is there anyway of telling what the casting is made of?
David 46
post Jun 20 2014, 07:17 AM
Joined: 27-Sep 08

I do not know of any way just by looking at it, Sorry. What I can tell you is if you start a Tig Arc and the glow around the Arc is green then it is more than likely a Si Casting if the glow is blue there is a high % of Mg in the cast.


post Dec 28 2020, 07:19 PM
Joined: 27-Dec 20

Hi lovinlife, I know this was years ago so don't know even if you are still on this forum but i have the same issue, just wanted to know how you got on with brazing of the carb.


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