Referring to them as 2nd generation was probably misleading, some call them early/late EVO's and there is no single year for cutoff.
Early/late may be more descriptive. All of the following should be considered my opinion only and you know what they say about opinions.....everybody has one.

Keep in mind the MoCo likes to use up parts in the bins at the assembly plant so not all engines during the same model years got the same upgrades/changes. The earliest EVO's used a lot of left over Shovel Head parts.

As far as changes in design, there are none I would put in the "Major" category.
1993 (I beleive) brought one of the biggest changes.
The heads were changed to allow case pressure to vent more efficiently through the tubes connected to the induction system breather (Air cleaner)
This possibly alleviated enough pressure to correct the issues with early EVO Base gasket leakage.
Crank and cam bearings were greatly improved after 1987 (I beleive).

As a rule of thumb, the later the EVO the better, IMO 1993 on, This is what I consider the best of the best or 2nd generation EVO's.
I don't know of any major changes in the engine after 1993. All EVO's are great engines. Aside from base gasket leakage, which in my opinion is not a major problem, I know of no major flaws in the design from 1984-1998(9).
I just personally prefer the later models due to the many minor improvements made during the span of EVO production.

That's about all I know.

If you have a '93 you have one of the best engines the MoCo made.

This is a list of the changes from "KiwiDave" hope this helps

84-92 Evo had crankcase breather set-up.

Model years 1993-up had ''umbrella'' valves in the rocker boxes to scavenge excess oil/mist..so-called ''head-breather'' set-up. Gaskets in that area did change to accommodate that, but you can use the late style gaskets on an early style Evo top end if you are handy with a Stanley knife! Some 1992 model bikes came with late style parts but still breathed through the crankcase hose through to air intake (swapped for a hose to ground or a hose to a little filter by 99% of owners). Those late-style rocker boxes etc will prob be '' -92''.

Base gaskets were continually upgraded through lifetime of the Evo, this is due to the one recurring pain in the ***, gasket weep at base of cylinders. Cylinder studs and 84-89 clutch hub were also vastly improved by the MoCo later on.

The clutch release set-up changed for 1987 to cable-in-sidecover ball-and-ramp set-up. Prior to that, earliest Evos had the decades-old release lever on the top of tranny.

The clutch design was changed in 1990 model year from a tapered shaft to a splined shaft.

Starter jackshaft set-up and thus new inner primary appeared around 1993.

Fuel injection arrived on some models in 1995/6.

 

Resurrecting an old thread...but yeah...I have a 1998 EVO RG...the last of the batch. I love this bike. I just rebuilt the top end after a cam bearing seal went bad and other than the base gasket weep (new since I rebuilt it... and I'm debating tearing it down again to make it go away) it's ticking just fine at 60K.

 

I'm not normally a Shark Nose fan, but there are some bikes here that look outstanding!

Bigtones, what pipes do you have on your's?

 

My converted 89 FLHS to FLTC

 

here is my FLT its a 91 (bottom breathing EVO) but I love here any way!

 

What the hell huh? I mean it's only a 9yr old thread. Nice looking scoot DG.

 

Older the better.

 

Here is the last TourGlide......

 

Here is my 1994 Tour Glide:

 

Nice!