Die cast parts

[Maicojames]

Hello all. I am currently buffing some vintage motorcycle parts. These particular parts are Bultaco engine covers, brake backing plates, and triple clamps, levers etc. I am happy with the levers, and triple clamps.

However, both the engine covers, backing plates, and fork sliders are coming out dull. I am sanding w/orbital 150, 320-then 320 wet, 400 wet-then spiral wheel , black, spiral wheel brown-I have not gone to the wht compound yet, as these parts have not yet got a reasonable shine from the first cuts.

Also, as I sand and polish and buff I am exposing some pits-some go all the way through. Are these pcs cast with only a small thickness of solid material on the outside? I have had more success with rough cast parts, which I have smoothed.

Any help appreciated, I'll bet someone else here has buffed some Bultaco parts before.
Thank you, James

[mpierich]

Originally Posted by Maicojames

Hello all. I am currently buffing some vintage motorcycle parts. These particular parts are Bultaco engine covers, brake backing plates, and triple clamps, levers etc. I am happy with the levers, and triple clamps.

However, both the engine covers, backing plates, and fork sliders are coming out dull. I am sanding w/orbital 150, 320-then 320 wet, 400 wet-then spiral wheel , black, spiral wheel brown-I have not gone to the wht compound yet, as these parts have not yet got a reasonable shine from the first cuts.

Also, as I sand and polish and buff I am exposing some pits-some go all the way through. Are these pcs cast with only a small thickness of solid material on the outside? I have had more success with rough cast parts, which I have smoothed.

Any help appreciated, I'll bet someone else here has buffed some Bultaco parts before.
Thank you, James

That's a puzzler right there, James. Some folks go higher with the sanding, but what you're describing is pretty much what I do every day for such items, and I usually hear no complaints from customers. All I can suggest is to try skipping the tripoli and go straight from emery to white rouge, and/or try a loose cotton wheel instead of the spiral. I have found that sometimes the tripoli can cause a haze.

As for the pores...if you've ever poured concrete, you know that the top surface is always trowelled smooth and hard, but there can still be honeycombed areas inside. In general, you can forget about trying to get them out..the deeper you go, the more of them you will see. Only way I kow to get rid of them is to copper plate the piece to fill the pores, polish and then chrome plate.

[Maicojames]

Thanks for the help. I guess I will try sanding some more. I used be a an autobody guy, so I thought my sanding was pretty thorough, though I may be able to get it better.

Tripoli haze? I will try to remove it with a good cleaning and wht compound. I always liked the cutting action of tripli on a spiral wheel. In fact, on most pcs-this gave a really nice finish. I have had little success with loose wheels-they just seem to haze the part-only after wht on a spiral have I gotten much out of it.

I have warned customer about the porosity in these castings(they are my vintage mx friends anyway). They think it loks good....only if the light hits it the right direction-and this will be a display bike for a while before it is raced.
After this, I think I will try to stay away from the Bultaco parts if possible-have you done some Bultaco parts? It's just that these bikes had the most polished aluminum of the vintage bikes, so it may be hard to refuse them-and keep working for moto money.

Thanks, James

[baz]

i could do a (copy paste) of what mpierich wrote as it reflects my opinion.
i have never done bultaco parts but have done lots of older castings , and yes some were very porous but also some of them do not end up as bright as others
because of the material used when casting the parts.
your customers have to understand that there is only so much you can do with some parts, unless they want to have them plated like mpierich wrote.

[mpierich]

Originally Posted by Maicojames

After this, I think I will try to stay away from the Bultaco parts if possible-have you done some Bultaco parts? It's just that these bikes had the most polished aluminum of the vintage bikes, so it may be hard to refuse them-and keep working for moto money.

I haven't gotten many dirt bike parts to do yet - but, Maicos and Bultacos used to polish _me_ off on a regular basis when I raced. To give you an idea, I quit racing around the time the Honda Elsinores came out - I'm a dinosaur. I ran a 450 Desmo Ducati (a real man's bike, but too heavy to win except on the TT track).

Good luck, and try to keep the broken bones to a minimum...

[mpierich]

Originally Posted by baz

i could do a (copy paste) of what mpierich wrote as it reflects my opinion.

Well thanks Baz, that's quite a compliment since I hold your opinion in high regard.

[Maicojames]

Originally Posted by mpierich

I haven't gotten many dirt bike parts to do yet - but, Maicos and Bultacos used to polish _me_ off on a regular basis when I raced. To give you an idea, I quit racing around the time the Honda Elsinores came out - I'm a dinosaur. I ran a 450 Desmo Ducati (a real man's bike, but too heavy to win except on the TT track).

Good luck, and try to keep the broken bones to a minimum...

I was five when the 250 Elsinore came out-pretty big deal, but not as big as the next year(74)when the 125 Elsie came out. I seldom saw another brand 125 all summer.

[baz]

Originally Posted by mpierich

I haven't gotten many dirt bike parts to do yet - but, Maicos and Bultacos used to polish _me_ off on a regular basis when I raced. To give you an idea, I quit racing around the time the Honda Elsinores came out - I'm a dinosaur. I ran a 450 Desmo Ducati (a real man's bike, but too heavy to win except on the TT track).

Good luck, and try to keep the broken bones to a minimum...

i did drive a elsinore 125 if my memory is good , and i drove once a JAWA CZ400
if you ever heard of that ,quite fast bike for those years. i think that was around 1975, but also very heavy

[mpierich]

Originally Posted by baz

i did drive a elsinore 125 if my memory is good , and i drove once a JAWA CZ400
if you ever heard of that ,quite fast bike for those years. i think that was around 1975, but also very heavy

I hated the Elsinores because they were so light they beat almost everything on the track. Sure I've seen Jawas. I was thinking, it would be cool to polish a Hodaka fuel tank but they sure are rare any more.

[baz]

Originally Posted by mpierich

I hated the Elsinores because they were so light they beat almost everything on the track. Sure I've seen Jawas. I was thinking, it would be cool to polish a Hodaka fuel tank but they sure are rare any more.

never saw one in my area