The 125 could be 86 or 87. They were pretty loose with it, but the general idea is that Kawi changed the letter when the bike got a major update, and the number when they got a minor update.
125s:
82 = B1.
82 = B2.
Then a big update in 84 made it the C.
The 84 model was moderately updated for 85, but Kawi decided it was enough to call it the KX125D.
Big update in 86 made the 86 model the E.
Minor update for 87 = E2.
Big update for 88 = F.
Minor update for 89 made it into the G.
The easiest way to pick the 86 from the 87 is the frame downtube/exhaust port. The 86 has a single downtube with a side exhaust port, while the 87 has a split downtube and centre exhaust port.
The 86 LHS sidecover is also the air box lid, while in 87 the sidecover is separate and you access the air filter from under the seat. There's also a difference in the rear subframe mounting points for side covers - a change from welded on tabs, to having the captive nuts directly in the subframe tubes.
