How to repiar small damged areas inside an engine case?

[blaat!]

I have a couple small areas inside the case on my 250 narrow case that are damaged (around kick-start bushing and one of the bosses for a side cover bolt). I'm planning to machine out the damaged areas, fab up a couple small parts, then have the new parts welded in.

These are my questions:

1. What alloy are the cases are made of?

2. What material should I use to fab the new parts from? (thinking good ol' 6061 Aluminum)

3. Is TIG welding using an experienced welder the way to go?


Anybody been through this before?

Thanks!

-Jim

[wcorey]

Could you elaborate on "small"? Most small damage can be just filled in/built up with weld...


Bill

[Rick]

As Bill said, weld it up if you can.
To answer your questions, 6051 welds OK- maybe not as nice as 5xxx series, it's almost impossible to say what alloy your cases were cast from, and an experienced weldor with a TIG would be fine.
The problem with welding in a chunk of 6051 is choosing a filler rod material- what works best for the cast case may not be the best choice for the 6051- your weldor should know what to do. After welding, the 6051 will have lost lots of it's mechanical strength advantage over the cast, so it won't be much of an improvement over piling in some filler rod except for the possible heat distortion.
I'll be welding some cases later on, if you can wait I'll let you know what I find- my choice is piling in a huge amount of filler rod- and heat- or machining a plug.
Rick

[ecurbruce]

Jim,
I had my 250NC welded sometime last year by my local aluminum fabricating and welding shop. He TIG welded with 5356-it has a little magnesuim in it. He said it is good for cast aluminum and is easy to machine. My cases were broken in the boss for the clutch lever from a fast moving broken chain.
I assume you're welding on empty cases, and would recommend bolting as much of the cases together before welding to minimize warpage. Even the outer covers could be bolted on if not in the way of the welding job. The guy who welded mine didn't find it necessary to pre-heat the cases, and did a fine job with that method.
Bruce.

[blaat!]

Thanks All,
My cases are almost completely disassembled at this point. Sounds like I should find a good local aluminum/TIG welder (anybody know of one in Massachusetts?) and get his recommendation for what material to fab the fixes out of. He could probably do a test weld where I plan to machine out the damaged area. I could just build up the weld, but I'm afraid of the heat distortion because of the location (near the side cover mating surface) and because of the size of the repair. I think it will be a cleaner fix if I machine out the old, fab up the new, and have a clean weld at the joint.

Thanks for the detailed info Bruce. I looked up 5356 wire and it looks to be a good choice for 6061 as well. I'll confirm with the welder before doing anything.

-Jim