Magnesium effect surface.

...but don't use a ferrous blast media. That can promote corrosion due to surface contamination.
Some say that a quick rinse in acid will resolve this problem but I have no experience of that.
 
Please explain a little more.
Is that the color of the metal after blasting with no further treatment?
I have a cover that was heavily corroded from riding in the rain etc, I sanded and painted it silver to hide the corrosion. If it would come up like that with vapor blasting then that'll be the next treatment.
Else what is the treatment after blasting?
 
Peder and Lavermax talk about aluminium replica parts that they want to finish to look like magnesium. I bet yours is a magnesium one. All you need to do is blast it and wait, as it will turn grey again with time.

Marnix
 
MarnixSFC said:
Peder and Lavermax talk about aluminium replica parts that they want to finish to look like magnesium. I bet yours is a magnesium one. All you need to do is blast it and wait, as it will turn grey again with time.

Marnix
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Depending on the composition of the magnesium base material, it may even get a slight golden sheen. All part of the natural oxidation process that forms a corrosion-proof layer over the surface. This won't stop aggresive chemicals such as road salt from attacking the magnesium, but general environmental influences should be harmless.

Alloy can be blasted and anodised to replicate the aged magnesium look. The selector cover in the pic is a factory magnesium original.

piet


PICT0060.JPG
 
I’ve found the original magnesium below ready to be machined.
What do you think about ?
Is it a good piece ? Could be a problem machine this piece after 50 years ?
I think it is a quite rare component and i would like buy it 😊
 

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Machining will show if it's OK or not. Casting flaws rarely show on the outsides.

If you have the tooling, go for it! If it hasn't been stored at the bottom of a lake, what could possibly go wrong? It's not a highly stressed component...

piet
 
I knew a guy who had a works RG500 but said it would never run now as it had magnesium components/covers that would now be porous.
I know the shelf life of magnesium wheels is about 5 years so i would b wary of using mag parts unless you know the history etc.
 
Structural or load bearing pieces, yeah, age related deterioration means you shouldn;t use them. Save them for display.
Covers and non structural pieces, not really a problem. Covers can be made oiltight with a suitable paint on the inside.

Any Magnesium piece should really have a dichromate coating to prevent corrosion.
 
I know the theory, and I‘m aware of the issues with certain magnesium cast wheels, but can tell you from my own and other’s experience that the magnesium alloy that Laverda used in their own FLAM foundry, named Elektron, is strong and doesn’t need to be painted to preserve it. It turns grey and that’s it.
For instance, I have yet to see the first SFC rear hub break. The sprocket carriers can break tabs which is usually the result of people who forget to put the spacer between carrier and hub, resulting in the two parts rubbing each other, resulting in cracking and breaking.

Marnix
 
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Components that have been slimmed or constructed to just barely able to manage their designated loads, and then made from magnesium alloys as in engine casings, can pose problems, especially if they've led a hard life and haven't been looked after well.

Lots of early VW Beetle gearboxes still giving good service, their shells were cast in Elektron. Cheap and easy resources for special builders in the '50s and '60s!

The Laverda marque is hardly renowned for lightweight components, more for rugged durability. I'd have no problems at all using the mag SFC hubs. Even the stone-age Fontana hubs in my factory-engined SFC racer checked out fine, I don't spare a second thought over them. The mag covers on the factory engine are also just fine, no signs at all of weakening. In fact, I'm rather astonished at how sturdy they are, as they are cast to exactly the same patterns as their aluminium counterparts.

Reckon a 45 year-old gearbox cover casting could go on indefinitely.

piet
 
Paddy said:
I had some magnesium carbs (dellorto) and i wanted to get them zinc chromate finished but is no longer done a s its carcinogenic so i had them Cerakoted as they would corrode as you looked at them when they were bare metal.

Before in Zinc chromate
View attachment 68692

After Cerakoted
View attachment 68691
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I can get zinc-chromate and cadmium plating here in Canada thanks to some aviation connections ....... but with the look of that cerakote on those carbs, why bother?
I use cad plating for some bolts as it gives them the "original finish" look that Laverda hardware came with ..... plus the torque specs are achieved correctly with cad plated bolts.

Jim
 
The funny thing was jim, people ask about £300 each for these carbs on en e-bay ;-) in very used condition......
I couldn't get £300 the pair for these fully rebuilt so i still have then 3 years later ..lol ( the slides and cerakote cost £200 )
I think they were used on Rotax engines , they are very light :-)
 
Paddy said:
The funny thing was jim, people ask about £300 each for these carbs on en e-bay ;-) in very used condition......
I couldn't get £300 the pair for these fully rebuilt so i still have then 3 years later ..lol ( the slides and cerakote cost £200 )
I think they were used on Rotax engines , they are very light :)
Click to expand...
Just say they are for an MV factory racebike. You can probably get 3000 quid for them!

Jim
 
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