Welding a Stihl Contra (090)

[farmhard]

Hi all, I need to weld a clutch cover on a Contra approx 1957/8. Usually I use aluminum TIG rod with flux but I tried welding with Alladdin which I believe is a Zinc alloy rod. I experienced porosity and cracking. The cover was cool enough to touch by hand and I would hear pops as it contracted and found cracks when filing. Other areas did not crack. Certain areas I would push the rod into to penetrate and it would work and other areas after I pulled the torch away would lift up and bubbe. An array off issue with this. I had a friend who is a welder that was not able to weld an 08. I can replace the cover but would like to keep the original.
Any suggestions?

 

[Stihl99]

What, you tried to braze the clutch cover?
That is magnesium and with your saw being so old it is most likely a better high end grade of magnesium than what we get today.
That requires deep cleaning, striping off all paints, oils, etc, then use scrotch brite to clean and prep the areas, and then TIG weld it not try to braze it.

 

[farmhard]

What, you tried to braze the clutch cover?
That is magnesium and with your saw being so old it is most likely a better high end grade of magnesium than what we get today.
That requires deep cleaning, striping off all paints, oils, etc, then use scrotch brite to clean and prep the areas, and then TIG weld it not try to braze it.

Magnesium can be gas welded, I've done AZ31B-0 in the past. The Alladdin rod was a fail but I normally use it on pot metals and not being sure of the alloy here.....I guess I'm going to have to order some flux and try magnesium rod. Perhaps I should rephrase my initial question to what is the specific alloy?

 

[Stihl99]

Magnesium can be gas welded, I've done AZ31B-0 in the past. The Alladdin rod was a fail but I normally use it on pot metals and not being sure of the alloy here.....I guess I'm going to have to order some flux and try magnesium rod. Perhaps I should rephrase my initial question to what is the specific alloy?

But brazing will cause you to have bubbles and the alloy will get dirty.
Tig welding is much better than brazing, just keep the tungsten rod from making contact, just work your puddle back and fourth putting in you bead.
Now with that being said, V-groove the cracks a little bit, a penetrating weld is the only weld to survive flush grinding and vibration if you run the saw anymore.