Topic: Anodizing carb bodies?

[jalfonso]

I saw a post of a bike which had the carbs painted black.  I've been considering anodizing the carb bodies.  Has anyone had that done?  Any possible problems I need to be concerned about?

Thanks.

John

[BobbyR]

I am not sure that the carb bodies are aluminum, I have read posts that describe them as some mystery metal. I would try a spare piece first. There are spray paints that give the anodized look how good they look I am not sure, how well they will hold up is another consideration. 

[754]

Castings dont anodize well, very splotchy. That and any anodizer may be reluctant to do them.. Cant have any steel   in or on the parts  when anodizing either.

 To the best of my recollection, there are plastic guide pins in the body for the slide, you dont want them to vaporise!

 paint the carbs..

[FunJimmy]

I recently had my front hub anodized and with excellent results.
My anodizer said that cast aluminum is unpredictable at the best of times.
You can increase the chances of a successful job by polishing the parts.
A tight polished surface will anodize more consistently. 
When I asked him what to expect he said that cast aluminum will often go very dark or even black.
Considering you want black, I’d say give it a try, but 754 is right, there can’t be any other metal parts on your carb bodies.

[Steve F]

I've always been under the impression that the carb bodies are die-cast zinc, and have no aluminum in them at all.  Plus, before any anodizing is done, they have to acid etch them before they proceed, which means all surfaces get etched, including the bores for the sliders....not good.  Brass passage plugs and the pins for the slides get eaten away in the process too.  In other words, junk carbs.  Paint may be the only way or maybe powder coating would be possible.  If they were mine, they'd get a polishing only.

[FunJimmy]

Steve

The anodizing process takes nothing away from the materials. In fact hard anodizing (left for extended periods) adds to the materials, ie: bearing bores get tighter. Almost 1 thou tighter.

[754]

Actually 1/2 in and 1/2 out..the buildup..usually only a couple tenths..

 Hard anodize is thicker though, and way TOUGHER..

What about the carbs tough, it there not a plastic nub in there ??

[heffay]

If they were mine, they'd get a polishing only.

ditto

[TwoTired]

Steve

The anodizing process takes nothing away from the materials. In fact hard anodizing (left for extended periods) adds to the materials, ie: bearing bores get tighter. Almost 1 thou tighter.

Aluminum anodizing is a conversion of the aluminum surface to aluminum oxide.  Therefore, aluminum is lost in the process.  Pure Aluminum oxide is transparent.  Dyes are added to make practically any color you want.

I am all but certain that carb bodies are NOT pure aluminum.

Cheers,

[FunJimmy]

Converted to aluminum oxide, not removed. It was also implied that the aluminum was etched and therefore a loss of material was a result of the etching.

[754]

I got an anodizer About 600 ft from my shop. He is not too keen on small batches and has a 60 dollar minimum.

I got a few bits around the shop hard anodized when we did some gas cap bungs I made for LAVERDA's. We also anodized some brake pistons. That is what Laverda uses. The gas threaded flange part we did was steel, and we made it out of aluminum with hard anodize. The gas cap is aluminum, so we opted for disimilar to prevent problems.

Funjimmy are you using Surftech?

[Steve F]

Steve

The anodizing process takes nothing away from the materials. In fact hard anodizing (left for extended periods) adds to the materials, ie: bearing bores get tighter. Almost 1 thou tighter.

It's the prep process, i.e. acid dip. It's essential for a good anodizing job. I worked for a place that made model aircraft retractable landing gear and such and they would have the valves and other things anodized, which would require the external threads and any bores to allow for the acid process which would eat away at the base metal.  We had to machine the bores for the pistons undersize so we could clean them up after the anodizing and get them smooth and to size without any concerns for the acid dip.  We always had to specify "light acid dip" on the work order so we had usable parts when they came back.

[turboguzzi]

to my best knowlege bodies of seventies carbs were often cast in some sort of Zink alloy (I think mazak is the german trade name) so they could resist the dry wear fo the slides.

Even if they were alluminum, at least decorative anodizing does remove some material. I also remember from my machining lessons in tech school that we honed boles to the exact measure after anodizing. Hard anodizing might be different but not so sure that's what you'd want for carb bodies.

TG

[jalfonso]

Thanks for all the replies.  It give me more information to consider. 

Steve F:  My other alternative to anodizing was polishing.  I'll probably just polish the carbs and Zoop Seal them afterwards.

Thanks again everyone for the information.

John