Gear perhaps...? The round things with various numbers of teeth on them placed on the main and layshaft inside the gearbox. The ones that makes the bike go at different speeds. Internal parts of a motorcycle was never in my englishbooks at school. A flaw in the swedish education system no doubt
I have learned a lot of technincal words but sometimes get them confused. Partly because sometimes different parts might have the same names i swedish and three different names in english. And sometimes there are three different names i swedish and just one collective name in english.