J is 1982, K is 1983, carbs are the only main difference I think.
the difference is the Yamaha is better
The only difference I see is the di version includes the ac power adapter.
The timing in the CDI unit.
the numbers
The Yamaha U3 is slightly larger than the Yamaha U1, this is the most significant difference. The larger size of the U3 results in longer strings and consequently to a richer and warmer sound.
about 25 to 35lbs depending on the year.
the L ,LWland LE has bigger tires than a E
The 620 is large bore while the 640 is medium bore.
Apparently the Paficica 012 replaces the EG 112 - that is the only difference
The differences between Yamaha and Honda overall aren't many. Both are Japanese based companies which specialize in ATV's, motorcycles and boats. The biggest general difference is Honda also makes cars (Yamaha doesn't) and Yamaha produces snowmobiles (Honda doesn't).
Just the looks. Classic is lower to the ground.
WaveRunner is made by Yamaha, Jet Ski's are made by Kawasaki.