Aluminum stuck to steel.

[shenion]

Have a B&S 12HP engine here. Funny story. This thing busted a connecting rod. I drained the oil: first 1/3 quart of black slime, then 2/3 quart of nice clean oil.

So, after it went "bang" because they never changed the oil and let it run low; they thought adding oil would magically weld the 12 pieces of the connecting rod back together and it would run This is the second engine they blew up and is only 1.5 years old.

I bought it for parts, but the piston/sleeve is spotless. Counterbalance and main bearings look fine. So looks like it would only cost a new rod and some gaskets.

The old rod had destroyed itself. It did not chew up the crankshaft journal but there is a layer of aluminum that is "fused' to it.

I tried a brass brush and it did not do much. I trying to think of a way to get it off.

One idea is bead blasting it then polishing the journal. As the crank is hardened, I don't think that would hurt it.

Another idea is to heat it to lossen the aluminum. Do no want to risk annealing the crank.

Any ideas, maybe chemical, acids etc?

I do notice the part # for the rod has been superceded with a different part. Maybe they had issues

 

[Bsmith]

Yep, I have noticed the B & S engines have an ally con rod and no big end shell bearings which would normally have a coating of white metal for the crank journal to run in. Have seen big end shells battered but never deposits of them stuck to the crank. I think I would try emery tape on the journal to get rid of the deposits and finish with a very fine grit wet and dry sandpaper. Brian (",).

 

[R Kraft]

Muratic/hydrochloric acid is what is supposed to be used to remove aluminum welded to steel.
Usually to clean the cylinder walls,but it should work the same to clean a crank.
You should find a few references to using it on the internet.

 

[rtbcomp]

I think caustic soda (washing soda) will dissolve aluminium without touching the steel.

 

[hareng]

Just thinking that dump the bits in an old tray use some washing soda and connect electolytically overnight or more. Excellent for derusting.

 

[shenion]

Thanks, I had this bottle of muratic acid that has been sitting around. Forgot i had it.

A few drops on the crank and it fizzed like crazy. Did nothing on the steel. Had a drop fall on the counterweight connecting rod, put a divot in it before I could wash it off.

There is still a little bit left. Did a bit of polishing and it looks good. Hard part will be getting some kind of polishing wheel between the arms of the crank.

 

[the snooper]

Have seen big end shells battered but never deposits of them stuck to the crank. (",).

the above usually happens when the big end seizes up it then locks to the crank and breaks the con rod up

 

[R Kraft]

Usually to polish a crank, I use a thin strip of fine emery cloth, looped around and used like a fire bow string.
Robert

 

[shenion]

yes, that is what looks like happened. The rod end got twisted off the rod.

Just finished polishing it. The is still 2 hints of the damage as two long thin dark stripes. Does not seem to polish off but cant feel any raised or grooved ares.

Now just need to order the connecting rod.

Odd they have bearing rings on the counterweight journals. They look like steel, probably as the couterweight is cast iron. Have seen them fail as the top one is the first to get starved with low oil. That riuns the crank. I fugured that is what happened with this one, but was lucky.

 

[shenion]

Usually to polish a crank, I use a thin strip of fine emery cloth, looped around and used like a fire bow string.
Robert

I used polishing compound on some small cotton wheels. To do the area between the arms of the crank, I cut a long strip from an old pair of jeans. Folded it along its length in thirds, ran it over the compound then over the crank. Worked well.

 

[R Kraft]

The dark strips are heat bluing, just decorative.
As long as it is smooth, it should be fine.
Robert