In the broader sense, what Don said is correct. 3HE and 1WG generally refer to the FZR600s and 400s (respectively) that were sold in the U.S. However, these part prefixes are actually tied to the part first. In other words, the parts can be used across various models.
Case in point: The part number prefix that is stamped into the 3EN1 FZR400 is "3HE" (upper fairing). This is the same dual-lamp upper fairing that is used on the U.S. FZR600 for '89, '90, and '93 - '99.
Another simple example (or two): The dogbones that are used on the U.S. FZR600 are stamped "1WG". These are the same dogbones that were used on the 1st generation (1WG) FZR400 (the only model the U.S. received - '88, '89, and (with a few minor changes), '90). Speaking of the '90 400, one of the 2 major changes (other than the 4-pot front calipers) is the swingarm. The '90 swingarm is often referred to as a "Deltabox" swingarm. This swingarm is actually the same one that's found on the 3EN2 FZR400 (which was never imported to the U.S.). So... technically, this swingarm should be referred to as a 3EN2 swingarm...
These are just a couple examples. If you were to go through a fiche page to compare part numbers between the FZR600 and 400, you would see A LOT of crossover with these prefixes.
In the broad sense that Don was referring to, the prefixes are generally used like this to refer to the bikes (for the 400s and 600s):
3HE 600 - The FZR600 that was sold in the U.S. for all years ('89 - '99)
4JH 600 - The FZR600 that was sold in the U.K. from '94+ (?) - This is the same bike as the U.S. '95 & '96 YZF600
1WG 400 - The 1st generation FZR 400 that was sold in the U.S. from '88 - '90 (with a couple minor changes for '90)
2TK 400 - The 2nd generation FZR400 (not imported to the U.S.)
3EN1 400 - 3rd generation FZR400 (not imported to the U.S.)
3EN2 400 - 4th generation FZR400 (not imported to the U.S.)
3TJ 400 - 5th generation FZR400 - complete chassis overhaul (not imported to the U.S.)
Hope that helps!
