Monday, September 9, 2013

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. 

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