Early models use this type of bearing and the crankshaft does not have a 'right angled' shoulder for the bearing to sit up against (the top crank in the pic). This is the original type Innocenti crank which is NOT available as a new replacement spare part. This is the bearing that fits the flywheel flange with part number : 20950045 (see pic).
Later J50 models have a different type of crank with a right angled shoulder (indicated by the green pen in the pic.) and use bearing Item No. M218zz (NU204). This type of crank is available as a new replacement spare part : Item No.M55
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