Honda CB750 Sandcast
The Restoration Shop => Chrome - Anodizing and Other Metal Finish Procedures => Topic started by: Wayne on January 19, 2012, 12:13:46 pm
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Does anyone have any idea of what finish was used on short petcocks? I don't know if the one shown in the SOOC Restoration area is a NOS or reconditioned but it looks "rougher" than mine. Mine appears to be more like a carb body finish, much smoother. Any ideas on making it look like new again. I had to get a new bowl and they just don't match.
(http://cb750sandcastonly.com//images/Early%20Petcock.JPG)
(http://cb750sandcastonly.com/coppermine/albums/userpics/10001/petcock_new_bowl.jpg)
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I'm thinking that the nameplate and screws are zinc plated. I'm planning on trying soda blasting on the rest unless I can find something that looks more original. I'm not sure what that is though unless new petcocks look like the old ones did.
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I was thinking along those lines Mark. The one in the pic looks like bright zinc or paint??? Look in the upper right. Looks like a spot got missed, or is it a shadow?
Darn small screws to have plated! ;) I'm sure my plater would have lost those! I think I'll try hitting the body of my petcock with some soda and see what happens.
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I went ahead and soda blasted an area on one side. I just used kitchen baking soda rather than commercial grade blasting soda. It's bloody cold out here so I didn't spend much time on it! Not bad for a few minutes work and it appears to hold that uneven finish like a carb body would have. You kind kind of see that rainbow?? effect in some areas. I'm not sure what that is called. Maybe with some commercial grade media, an older bowl, zinc screws and nameplate we will be in business Mark! Now, I really should get on with some serious work! ;)
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The screws and the plate on/off/res are, for sure, zinc plated.
For the body, you can use the ultrasonic bath or any other product for carb degrease.
You can use also the cloridric acid, but in percentual solution with water, because it is aggressive and the alloy goes in sufference (smokes in the bath and can believe black).
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Fellas
Use methelene chloride for alloy. Ultrasonics is OK but really not a great process for finishing alloy. I've got a Crest UC tank and have used several speciality alloy cleaners but really not the best process IMHO.Soda is a good medium as it does little damage to hard surfaces BUT, make sure it's was off thoroughly KP
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Methylene Chloride? this is new to me, how is it best used to clean or finish aluminium?
.....is it commonly available?......liquid or solid etc?
New compounds are always interesting.
Mick............kettle738
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Good info but back to my original question. Were short petcocks coated (ie: zinc etc) or were they just cast? Like I said, the one attached to the candy red tank appears to have been coated or painted.
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The short neck on the red 19L is 232's. The short neck came with that 19L i bought on ebay. The tap & bowl are original finish. The spring retainer and the small screws, i had new plated with "clear," "bright" whatever we call that zinc finish. As it's been explained by zinc platers to me, "clear" and "bright are the same finish. How lusture can differ between batches depends on the various factors of the solution, age of solution, purity of solution, temperature of solution, etc (more factors than i can remember or know.) New petcocks i have seen, their plates really do look pretty much the same as the lusture on this "232 tap." Variables affecting how original parts appeared when new must be considered in determining what "restored lik original" should look like in any attempt to replicate actual original finish. Unfortunately, inablity to recreate or control these variables force us to make accept a final outcome that is as close to appearing original as we can possibly make. Sometimes we get it right on, sometimes we get it close and sometimes we have to try again.
Or, we make the machine the way we want it to suit our tastes.
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Good info but back to my original question. Were short petcocks coated (ie: zinc etc) or were they just cast? Like I said, the one attached to the candy red tank appears to have been coated or painted.
yep, we did get off the track. As far as I can see with mine, they are exactly the same as the later type which are pressure cast zinc alloy
Methelene chloride is the main component of good quality paint stripper and nasty stuff but like most nasty products, if handled correctly it is safe enough. KP
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The iridescent (rainbow) finish seen on the petcock and carbs could be 'flashing' resulting from the casting process... ?
This iridescent finish i have seen on carbs and petcocks, has been present in varying degrees to absent, so i am wondering if exposure to the elements/atmosphere breaks this finish down over time... ?
Or, depending on the casting batch, if some batches had more of an iridescent finish than other batches... ? Or this finish, depending on the batch, was more or less susceptible to breaking down to environmental exposure... ?
232's long choke arm carbs have a rather fresh appearing irridescent finish.
The petcock that came with the 19L tank i purchased off ebay had a flat finish; not to say when it was new it had an iridescent finish...
I've not seen a set of nos carbs, so i can't speak to what the finish on nos carbs would/could/should look like.
Nos petcocks i've seen, have this iridescent finish. I can only surmise "father time" took away the iridescence from the 232 petcock. Or, someone before me, cleaned that petcock, because cleaning will remove the iridescent finish.
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I've two spare nos carbs (#3 and#4) and also a complete set of carbs, NOS.
They have the iridescent finiture.
I think that the word "finiture" is not correct because they appears iridescent for the casting of the alloy and not for a successive treatment.
A good bath with chemical product or an ultrasonic bath can redone the early iridescent appearence.
The sand blasting treatment is too aggressive and the iridescent light can be lost.
I think that this iridescent lumi is what remains in the surface during the casting process when the metal goes to solid status, pheraps a gas that come off high temp fusion.
I think this.
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Well, I think that about sums it up! Duplicating the "iridescent" look after casting appears to be impossible. Short of having NOS parts I guess we settle for "close" or as Steve puts it "making it the way we want to suite our tastes". My Petcock is decent so it should clean up pretty good. Like I said, I may have to get a used bowl to match it better.
My carbs are another story. They are going to take some serious work! :(
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A couple other things i will say, appears the carb bodies and the fuel tap/bowl may not be the same material as carb float bowls... ?
The carb bodies/fuel tap (operative word is "appear") to be more of a "pot metal" material or some other (different?) mixture of metals than what we typically see as or call aluminium... ? Whereas, the carb float bowls appear to be actual aluminium... ?
Seems the carbs are some sort of aluminium mixture, but it "seems" the metal the carb bodies and fuel tap are composed of "appears" not the aluminium we see on engine cases... ?
If the above could be the case, this may explain the irridescent finish on the parts we're discussing results from the casting process as it affects the mixture of metals these parts are composed of... ?
All i know for sure is the iridescent finish can be all too easily removed. And, i've seen varying degrees of iridesence, "appearing" to be degraded or absent from the hand of father time or industrious cleaning.
I am going to speculate, because the carb bodies/fuel tap may not be the same metal composition as other aluminium parts, the casting process of these parts results in a surface "rainbow" or irridescent sheen... ? This could certainly account for Riccardo's very plausible theory of gas coming off the cooling metal, resulting in the irridescent finish due to heat and metal composition.
Somewhere in my "travels," my memory seems to think there is a reason why carb bodies/fuel taps are not made of "pure" aluminium, the surfaces being exposed to gas/air/heat to prevent metal degradation and distortion... ? And, i believe pure aluminium could tend to "gall" with the up and down action of the carb slides... So, perhaps the metal composition of the carb bodies has some element of lubricity... ?
Not knowing much about what i'm trying to talk about and/or being unable to recall anymore than what i'm already speculating and/or trying to remember, i think i'll stop here, while i'm still ahead. Maybe... :)
PS - Thinking "out loud"... Could the iridescent finish be recreated by heating the parts at a safe lower temp for an extended period of time followed by room temp cooling ? Probably not, since the iridescent sheen is probably caused by gases trapped while the cooling part is still in the mold...
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Which brings up another thought...
I can't recall seeing any fuel tap bowls with irridescent finish... What i have seen on every new bowl i can remember is the sort of "dusty" "milky' finish such as on Wayne's new bowl. And, i do not recall seeing that dusty milky finish on the tap body.
For that matter, i'm not sure i can recall fuel tap bodies with the irridescent finish... only carb bodies... However, this idea does not make sense, from the standpoint the tap and carbs are exposed to gas. The tap body and the carb bodies are exposed to gasoline, so they should be the same composition. But, i'm a little numb from perhaps overthinking all this, not really knowing in full what i'm talking about... ;D
For some reason, i've always really liked the irridescent finish on the carbs... :) I'm sticking with that !
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Re: Restoration by Puccio from Tuscany
« Reply #54 on: December 01, 2011, 03:30:30 PM »
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Sorry, I forgot.....
Also the Carbs must be restored.
Where I work there is ultrasonic bath, this is the better solution for wash the carbs.
Before to insert the carbs is necessary put the special liquid in the water and to warm
before the bath...
https://lh5.googleusercontent.com/-lOUjbfp1AKw/TtBLkeOHd2I/AAAAAAAABDY/c9ngyS2DJbI/s800/211120111202.jpg
After the bath I saw the the color is changed.
Some halo of blue/purple is possible to see now.
https://lh5.googleusercontent.com/-M5nBlE50hWQ/Ttadskn0fqI/AAAAAAAABF8/1wMuHyOPFfY/s800/291120111259.jpg
after a short pass with special ultra fine sponge (steel), the color is changed to turn in new this...
https://lh4.googleusercontent.com/-WDOfiEkEYWs/TtadsK5lDUI/AAAAAAAABF4/oz5-JpOoYiY/s800/291120111258.jpg
This is a Puccio's reply, posted the last month.
As we see, the body carb has received a chemical ultrasonic bath and, after the bruscing surface treatment by Puccio, the raimbow/iridescent was lost.
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riccardo
I forgot about that post. My carb's may come up better than I thought! I'll have to see if I can find someone with an ultrasonic bath locally. Thanks!