Mag Rot - What Would You Do?

[Vintage Engine Repairs]

My 020AV has rot inside the oil tank.

I have tried fuel sloshing and compressed air, but really, it needs a split down, grind away the rot and JB weld it back up.

My concern is that the parts for this saw are very hard to source and right now the OEM seals are excellent and hold pressure and vac.

What would you do? Split it and replace bearings, seals, gaskets and repair the rot, or leave it and just clean it as best as I can?



thanks guys.

 

[CausticUC]

Use liquid fuel tank sealer.

 

[SteveSr]

My 020AV has rot inside the oil tank.

Stupid question... How would mag rot get inside the oil tank? Did it work its way in from the outside? on a seam perhaps? If so there may be more damage than first evident.

You might be able to save the seals when you split the case but at that age I wouldn't want to. Are they standard size seals?

 

[Yukon Stihl]

Inside the oil tank i wouldn't worry about it.
Leave it and keep the fact that it needs attention in mind as you look for more projects.Next thing you know you will find another for parts.
After years of hoarding saws to work on the 07S kept eluding me. I just finished a deal on #3,should have enough parts to make 2 runners and sell off the rest in parts.All 3 came to me in November.

 

[olyman]

Use liquid fuel tank sealer.

if theres a filter on the oil line, will plug it...………...

 

[banditt007]

What causes this?

 

[CausticUC]

if theres a filter on the oil line, will plug it...………...

Following usage instructions is always a great idea. It is made to seal failing fuel tanks, not flow through lines like some other "sealers" are.
Usually you disconnect all orifices, remove all filters and baffles, then you put some in the tank and rotate it around.

It is fairly viscous like honey or warm wax. It is a barrier coating.

 

[Mad Professor]

Stupid question... How would mag rot get inside the oil tank? Did it work its way in from the outside? on a seam perhaps? If so there may be more damage than first evident.

You might be able to save the seals when you split the case but at that age I wouldn't want to. Are they standard size seals?

What causes this?

Water reacts slowly with magnesium.

 

[AlterEgo]

Nothing.

use it.

 

[SteveSr]

Water reacts slowly with magnesium.

Hence my question... How did water get into something that likely had an oil film all over it unless it came from the outside?

 

[CausticUC]

Hence my question... How did water get into something that likely had an oil film all over it unless it came from the outside?

Condensation from temperature fluctuations in a non-full tank, this is a common issue in diesel, bunker, and home heating tanks that are not kept topped up.

 

[Vintage Engine Repairs]

Thanks for lots of responses. I’m not sure how it got In there as I only brought it a few days ago, but I presume it was condensation from temp fluctuations, though the fuel tank is spotless. Scratching my head on this one too!

 

[farmguywithasaw]

Used engine oil possibly as it becomes corrosive and probably got contaminated with water as well.

 

[farmguywithasaw]

Hence my question... How did water get into something that likely had an oil film all over it unless it came from the outside?

Oil floats on water so if it can get under the oil it will lift it off

 

[Vintage Engine Repairs]

Update, took some advice and decided to rinse it out lots with Shellite, a fine tipped vacuum and scrubbing to remove the gunk and see what’s left. It’s not good, but it’s not as bad as it looked previous. The worst affected is the oil galley barb which has rotten through, but still holding.
Because nothing is overly deep, I’m going to leave it and when I need to rebuild it for another reason, I’ll do a proper clean out, abrade the rotten mag with a wire wheel and then seal up with JB.

Thanks for the advice guys, much appreciated!
After a clean: