KIWI Mk2 I/C ENGINE BUILD

Part 3 By Vince Cutajar

E.T. Westbury specifies that the rocker arm bushes should be made from gunmetal  and not from brass. Now I have never used gunmetal so I do not know how it looks. I have found a piece of hexagonal bar (in the kit) suitable for the bushes but I suspect its brass and not gunmetal. Well, I would only be running for short periods so I guess if the bushes are made of brass, it would not make a lot of difference.

I faced off the hexagonal stock and it felt like brass. I then turned it down to 6mm diameter. According to the plans it should be the same thickness as the rocker arm, but I made it a tad longer as I suspect that the rocker arm might bind with the rocker arm pillar. I can always shorten it later on. I parted the part off and faced it.

Drilled the hole 1/64" off-centre and reamed it.

For the 3mm studs just took 3mm bar stock and cut it to length. There where no dimensions on the plans but it was easy to figure them out. Threaded both ends and that's all. The photo shows my method of keeping the die straight while threading. I just use an old collet chuck in the tailstock.
I started work on the crankcase breather system with a 12 mm brass bar stock and turned it down to 10.5mm. I then knurled the machined part and then continued turning down part of the knurl to 6mm. I threaded it 6mm Fine with a die. I then made a quick 6mm fine nut out of a piece of brass strip. I cut a shallow groove at the top of the thread (between thread and knurl) and inserted the thin nut I just made to clean up the thread. I left it there and reduced the thread length to dimension using the nut to clean the edge of the thread.
For the crankcase breather assembly body, I took a piece of 10mm brass and faced it off. Took some measurements for the breather holes. Put in dividing head and drilled six 1.5mm holes.
I cut down the breather body to size and reduced the side that goes into the crankcase to 6mm and then threaded it with a 6mm fine die. I then drilled and reamed the through hole 4mm. Reversed it in the chuck and with a 5mm slot drill increased the bore to the desired depth. Then tapped the first part of the 5mm hole 6mm fine. Yes, I should have drilled it 5.2 mm but brass is a bit forgiving. After tapping I passed again the 4mm reamer and then the 5mm slot drill to clean up the body of any burrs that might have been produced with the tap. Tested the cap and it fits nicely. I then parted the cap off as it was still attached to the bar stock and cleaned it up.
I next needed to put a 5mm Tufnol disc inside. I ordered a small sheet of 1mm Tufnol from Ebay; postage cost more than the Tufnol, but what can I do if I can't find it locally? Then machined a 5mm punch and die.

In the photo is the sheet, the breather parts and the punch and die. Not visible in the photo is a 3mm through hole in the die so that I can push out the punched out disc.

I bought in some metric ball bearings. The ones in the kit were 3/8 x 7/8 x 7/32. The ones I got were 10 x 19 x 5 (61800). I wanted open bearings (without shields) but could not find them, so I got them with rubber shields and removed the rubber. I hope I did not compromise them by doing that. In the photo the ones on the left are the original bearings and the ones on the right are the ones I bought.
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