Honda CB750 Sandcast

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ashimotok0

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Here are some parts I just bright zinc  plated. (then some were yellow chromate passivated as they were originally) Don't forget this was a UK Bike which was definitely a 'rider' for many years in grotty UK weather. All of these parts are original but painstakingly restored by me but apart from the plating chemicals and elbow grease abrasives, a few connectors and time!!!!!!!!! did not cost me anything. I only did the hose though because it had been replaced at some time and deemed safe to use. I also re-furbed the insides of the electrical parts (another story)

Here is the tip on plating the hose. Bind loads of electrical tape around the rubber, about 3 inches up from the banjo metal fittings. Use a combination of rubber washers and nuts and bolts to blank off the banjo holes. Test for tightness by immersing in really hot water and look for bubbles. If it bubbles then you must seal it properly. Dip in HCL ('brick acid' will do) for about 5 minutes to remove all of the old zinc plating. When the fizzing stops- remove immediately from acid and rinse and rinse in hot water. Wrap some copper from a copper heating pipe around the rubber hose to protect it whilst polishing (leave the tape on)  Polish with fine wire wool and buff with a dremel tool. If it's badly pitted, then I would trash it - its not worth saving it. When it is bright and shiny, degrease with solvent (I use isopropanol). Then dry. Then dip in strong caustic soda to further degrease (ten minutes). Rinse well in hot water. Dip in HCL again for about 1 minute. Rinse again in hot water.Carefully remove the bolts from the banjo holes without trying to handle the metal part.

Fellas, HCL does not generally affect brake hoses or rubber and having plated dozens of items over the years I don't see the need to go to that extent. It's just not necessary. Using a mild solution of HCL will clean the zinc off most metal. A buff, degrease, soapy detergent wash and final water rinse is about all that's needed to clean most items ready for plating. Sure you need to up the concentration a tad and extend the time for hard to shift stuff but a buff wheel will usually suffice. I use a metal cover over brake hose if I use a wire wheel and this gives a really nice finish and acid is generally used sparingly. Acid will pit metal really easily if too strong and left too long. KP

Hi KP - I don't understand your point - You say HCL does not affect rubber - So why not use mild HCL? - at least to 'pickle' before plating. This is recommended practice in every electroplating handbook that I have ever seen (or some use Sulphuric acid) The acid only needs to be mild. I sealed off the hose because I thought chemicals in inside may be dodgy and any attempt to plate inside woould be poor and may flake off into the brake fluid afterwards. To be quite honest brake hoses, unless in really good condition, should be replaced with NOS or new (just my 2 pence/cents worth)

Cheers

Ash
« Last Edit: November 23, 2010, 01:03:50 pm by ashimotok0 »


markb

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This is a great thread.  Will this work on the oil line ferrules?  Will it affect the aluminum ends?
Thanks,
Mark
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


ashimotok0

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Its all about masking really Mark. You should definitely not clean with caustic soda (I think you call it 'lye') it will react with the alloy. I have a scrap hose from A k7. I will be a guinea pig and plate it so you don't trash your precious early ones.BTW, I find the red wax off a 'Baby Bell' cheese can be used for masking too (one for the Brits that one  ;D)

Mark do you have any comments on the pic of my K0 rear wheel rim (see previous post on this thread)


cheers

Ash


markb

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Ash,
It looks like the rounded edge one to me also.  They are hard to get a good picture of.  I've been told to compare it to the front rim and if it's different then it's the rounded edge style.  I had one on my early diecast VIN 1012xxx.
Mark
« Last Edit: November 23, 2010, 02:53:22 pm by mark1b »
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


kp

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Using a mild solution of HCL will clean the zinc off most metal. Acid will pit metal really easily if too strong and left too long. KP
Hmmmm!   ??? Ash, You say why not use mild HCL. I think this is what I wrote "mild solution". Your thread didn't refer to mild HCL so I was making the point to use a mild solution. The other BIG issue relates to cracked or getting older hoses. Brake lines are made up of layers so I would be wary re the effects of strong acid on the various layers. I agree that using old hoses on a rider is not a good idea. Vic World doesn't do it either. However, and like me, there are lot in this group that don't ride their restorations and want to keep the authentic hoses.
Fellas, this is not rocket science but there are some do's and dont's. Ash is correct in saying to not put non-ferrous metals anywhere near a caustic solution but you can clean the oil hose ends of all zinc with care. When plating, I use soapy detergent rather than caustic solutions anyway. I've not done oil hoses but see no issue with doing what is suggested ............. do a dummy run first is good advice. KP
Yabba Dabba KP