Cleaning Aluminum

After soda blasting the aluminum I washed it to remove the residue. When it dried there was still baking soda coating it. I put it in the dishwasher for a heavy clean running the standard cycle with no soap. When it was finished the residue was gone but there were black streaks where the baking soda had washed out of the threaded holes. Upon researching “how to clean black streaks from aluminum” I found that truckers use “Purple Power” to clean their aluminum fuel tanks. I purchased this from my local Autozone store. They keep it behind the counter for commercial use even though it is listed on their web site. I purchased a gallon and gave it a try. It worked well, removing all of the streaking on the castings.

Next time I clean aluminum I will try soda blasting in my cabinet, although I am told this will not work well. I have also heard that walnut or plastic media blasting is a good solution for aluminum and will try them if I am not able to get the soda to function in my cabinet.  My fall back will be low pressure bead blasting or sending parts out for ultrasonic cleaning.

Soda Blasting and Cleaning

Now this is an area that I have had mixed luck with in the past. I have a hand held blaster with a top feed bin on it for aluminum oxide and glass beads. Most restorations I have seen used bead blasting to clean up the aluminum parts. The first BSA I restored was cleaned in this manner. I did not like the rough finish it left and I found it hard to keep clean. I wanted to keep the casting glaze on the aluminum so I decided to try something different. Soda blasting seemed to be the next logical step.

I put soda through my hand held unit and it worked alright, but plugged up quite a bit. The carburetors were done with this blaster. I also went through a lot of soda-blast media, which had been purchased from Harbor Freight. A friend of mine had a soda blasting unit which he loaned to me after I explained the issues I was having to him. It was a unit with no cabinet. It worked very well and I would not hesitate to use it again if I had a better place to operate it. Air pressure makes a significant difference in how well it cleans and if the work piece surface is abraded. I also found soda blasting could be used to clean up chrome. I did not do much experimentation with this, but I will in the future.

One thing I learned with soda blasting is that it kills grass and everything green it touches. I had a construction project going on in my back yard with plans to replant it so I was not too worried. With my new yard in place I no longer have a place to use this media. I will hire this out next time or try doing it in an enclosed cabinet.  Since the time I soda blasted my parts I have read about ultra-sonic cleaning. I will study this more to understand its pros & cons.  I have also purchased some walnut shell blasting media to try. Low pressure glass beading may also be a good method. More to follow.

Before and after pictures of the Monoblocs.  

The casting glaze remained if I did not set the air pressure to high. It did not clean as well as bead blasting.   

Rebuilding the Carbs

The 67 BSA Hornet came from Birmingham with Amal Monoblock carburetors on it. I was not familiar with this setup, but after studying the workshop manual they seem easy enough to understand. Taking the carburetors apart posed a problem as the slides were seized up in the bores. I soaked them with penetrating oil but could not get them loose. I finally pulled them out by using a lot of force. To clean up the bodies I cleaned them in kerosene and then soda blasted them, which worked quite well.

The bores were scored and were well worn. This was no surprise considering how rough the bike was when I started working on it. At that time I made the decision to send the bodies out for sleeves. I mailed them to Lund Machine in Snohomish, WA. Turnaround was quick and they looked very good upon their return. The bores were enlarged to clean up the surfaces and the slides were machined to accept a thin stainless steel tube. They operate very smooth with this new setup, although I have not run them on a bike.  One thing to consider when going this route is that the chokes can no longer be used. I never use chokes on my other bikes and did not consider this a problem. I am installing AMAL plugs in place of the choke cables and removing the choke slides.

All internal parts are still in production by AMAL and have been purchased for reassembly. I sent to England for these as the kits I found across the pond were more complete than the ones available in the US. Shipping was not too bad for small parts either. The last step for refinishing the carburetors is to get the screws and fittings CAD plated. I am sending them out with my other hardware hoping they will not get lost. Some of the parts are chrome plated and I will clean them up or purchase new ones as needed.

Cleaned up, new sleeves and ready to assemble.