Will a Honda cr125 jug fit cr80 bottom end?
Yes, but some modifications are required. The CR125 cylinder has a larger diameter than the CR80 cylinder, so the CR80 crankcase and cylinder head will need to be bored out to match the CR125 cylinder. The CR125 piston and rod will also need to be used. Additionally, the CR80 transmission will need to be modified to accommodate the CR125 powerband.