Because it was unaffordable for many small motorbike brands to develop and make a good engine block, many motorbike brands bought these blocks. One of these engine manufacturers was JAP. Because of their years of experience and many test possibilities, these engines were highly regarded and eagerly used by many motorbike brands and even used to break their world records.

This engine is a KOY/S this is a 500cc sport block with double exhaust from 1929. Engine needs revision as it is stuck at the moment but oil pump, magneto and the racing carburettor 15MDY are still on it.