The number 4 for identification is engraved on the head with a general bolt of strength 4.8T. This type of bolts is rare today and it doesn't come in many sizes.
A few of these bolts were used on the Kawasaki Z1 and two strokes with the reference 116Bxx-xx, but are not available for replacement, so this is the chance!
Two types of treatments are proposed:
- Trivalent plating treatment is a modern plating that looks similar to zinc without the chemical hazard and better consistency and corrosion resistance. This is the standard for Japanese manufacture and I recommand it for a perfect looking and lasting restoration.
- Chromate plating for resistance to corrosion. Electrogalvanizing is applied to the base, and then a chromate treatment using hexavalent chromium, which is a chemical conversion treatment, is applied. The chromate film changes its color from blue to yellow to red to red-green to green-brown to brownish brown as the chromate film immersion time of the zinc plating solution increases and the thickness of the chromate film increases. Hexavalent chromium is subject to RoHS regulations but still widely used. These are the few yellow bolts on our bikes.
Japanese vintage motorcycles, JIS screw, small head nut, small head bolt, pan head screw, honda, Kawasaki, Yamaha, Suzuki, Kawasaki 900 Z1, honda 750 CB K, Yamaha 350 rd, Suzuki 750 gt, zinc, stainless, acorn nut, black zinc, Japanese industrial standard, JIS screwdriver, engine bolt, flange bolt, 7 mark bolt
Bolt #4 Upset Head
M6 10 o 15 o 20 o 25 o 30 o 35 o 40 o 45 o 50 o