Part 23 By Vince Cutajar

I made the knob for the needle valve. For the needle valve I am actually going to use a needle. It is long and 1.2mm diameter. It's not a sewing needle but used for other things. I am sure it has a specific name in English but do not know what it is (Bodkin - ed). I sweated the top part of the needle with soft solder and then soft soldered it to the knob and cleaned up the excess needle sticking out of the knob.

Drilled the oil holes and air holes 1.5mm through the centre tube. Assembled the reservoir and filled with water to check for leaks and also the operation of the needle valve.

I made up a simple bracket for the oil reservoir.
I decided to make a D-bit which I intend to use on the carb to form the venturi. I made it from 8mm silver steel and hardened only. It worked out well and a trial cut on a piece of brass worked well. The following photos show the manufacture of the D-bit and the trial cut.
Next I started work on the carb casting. I had been playing around with it for two months and I just could not put it off any longer. I have been making mental notes regarding work holding and casting dimensions (which are all over the place).

So started work on making the hole for the throttle body. I clamped the casting by the small boss on the other side of the body and drilled from 5mm to 10mm in 1mm increments and then first using an 11mm and then a 12mm slot drill finished the hole. This should be 12.7mm according to the plans but left it at 12mm due to not enough material on the casting. I could have gone to 12.5mm but did not want to risk it.

Then using a boring tool I faced off the bottom of this hole. I also faced off the top of the hole with the same tool.

As you can see it is a bit off centre. Using a thin parting off tool I removed the excess material so that the hole will not look skewed.

I then drilled and reamed 5mm the hole through the boss. I did not do it before so as not to weaken the boss.

Managed to get some phosphor bronze for the throttle body. I needed 16mm diameter but could only find 22mm. What a waste!

First drilled and tapped 3mm and then formed the spigot. Then turned the throttle body. I then used this partial throttle body as a mandrel for the carb body. Cleaned up the other side of the carb body but at the end I had to remove the 3mm bolt holding the carb body to the mandrel. I used nylon tie wraps to hold the body to the mandrel and faced off the seat of the bolt.

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