*** NOTE   The 3HX series seems to be the start of EXUP.
Also, I am not sure how the 3HX relates to the FZR250 as they are only ever refered to as the 2KR or 3LN models.

FZR250 (2KR/2RF) 1986
The FZ250 PHAZER is the base form, it appears as a race replica, with the full cowl of FZR400 design.
Relationship of the frame between the engine improved from the FZ250 PHAZER,  the wheel and the
brake from the TZR250.

This FZR250 became explosive hit and the next year when it appears (1987) 28,000 units or more sold.

In regard to this early type FZR, after some selling it is improved minutely.
The improvements and the serial number which are modified are as follows.

FZR250 (2KR/2RF) 1986

FZR250 (3HX1/3HX2/3HX3)  1988

The model where the EXUP exhaust device is fitted.
What is EXUP ? It stands for EXHAUST ULTIMATE POWER. Developed by YAMAHA, the exup valve is a power
valve fitted to the exhaust system at the point where the four pipes join into one. It is driven by two cables from an
electric servo motor. The valve is set up to be almost shut off at idle to 4,000RPM and opens progressively to be fully
open at 10,000RPM.

Because of the valve timing required to get useful torque at high revs, there is little torque at low revs because the
exhaust valves open very early during the power stroke, letting the expanding gasses escape into the exhaust pipe
instead of pushing the pistons down to the bottom of the stroke.

The EXUP restricts the exhaust gasses at low revs, creating  a back pressure in the exhaust system which actually
restricts expanding gas from escaping from the cylinders creating more force on the pistons even though the exhaust
valves are open. As the revs increase so the EXUP valve opens as well, progressively reducing the back pressure until
at about 10,000rpm where the effect is not required. The net result of this is more torque is created at low revs than
would otherwise be available making the FZR much more rideable at low rpm.

EXUP is fitted to the FZR, YZF, R1 and R6

Not only this, performance is improved at the time with higher reving, modification of valve springs, improvement
of the road handling with the modification of the linkages of the rear suspension and movement et cetera. It is finely modified
to on the 6mm of step position.
Summer, sponsor color version of the NESCAFE AMERICANA color and the TECH 21 color being limited and being sold.
Also this model becomes the similar hit model as the first year , 20,000 units or more sells in year.

 FZR250 (3HX1/3HX2/3HX3)  1988

    FZR250R (3LN1) 1989 

The YZF and the FZR750 (the OW01) became the same design, standardized from the FZR1000 to the FZR250R,
but this design only 1 year had in addition to. This is the modification point when,  when almost everything changed,  the
aluminum delta box which lightens the frame, the engine and the double front disk. All this high reving conversion, new frame and the
improved brakes, improved handling considerably.

Sale quantity, 11,000 units and the rival CBR,   5,000 unit
Differences, rise of body price (4 ten thousand Yen), was the time when shrinking popularity of race replica  starts appearing.

  FZR250R (3LN1) 1989

FZR250R (3LN3/3LN5)  1990

This year which the FZR400RR appears and in order to make the design standardized, surroundings of the light and became projector
2 light system In addition, e.g., wall thickness of the frame is increased, operativity and maintainability improved e.g., modification
of the switches, the brake lever in 4 gradual adjustment modification and the oil filter becomes simultaneously with the improvement of
travelling efficiency the cartridge (I think that means it becomes a self contained screw on type). But the sacrifice is a 6 kilogram weight increase.
The 3LN3 1990 year color remain the same for the 3LN5 (1991), but the 3LN3 after the 3LN5 appearing that way being sold and continuing.
The frame and the swing arm of the 3LN3 are aluminium , but as for the 3LN5 the lead-lead in black paint, because the blue
becomes silver paint, note is necessary part interchangeably.
There are times which as for the 3LN3 at the time of 1990 sale, the hole 2 places each we would like to see on left and right outside the
swing arm, are, but it has stopped being 91 year model. You think this becomes standard of distinction of production time.
By the way, when it improves from 91 year model, does not designate this time, drops to 40 horsepower with with good relationship
also each manufacturer to become only colouring change, it was the time when replica sales becomes decisively reduced.
The sale quantity of 1990 was reduced by half to 8700.

FZR250R (3LN3/3LN5)  1990
 

FZR250R (3LN6) 1992

They are 40 horsepower self-restriction corresponding models which are sold in February of 1993.
As it modifies in 40 horsepower, red zone start position is modified from the 19500rpm to the 16500rpm and torque is
produced lower, this has improved fuel economy somewhat. In addition, acceleration efficiency improved with the
largest torque of 2.6kg-m, a 0.1kg-m improvment.
Among the model, it uses high revolution until recently with these modifications and when shift change is used, when
being, with this model excessively shift change do, it reached the point where it can travel.
In various senses it was the good motorcycle, but age are not appraised and have not succeeded because
of the times when it is tilted extremely in the ネイキッド, commercially. The sale quantity is thought to be1000. (CBR 3200)

FZR250R (3LN7)   1994

The last model appears in March of 1994.
As for this model, the color specification there is no modification with the sufficient model which modifies.
As for Yamaha, it is regrettable not to produce the super sport model in 4 stroke 250cc classes the after the this.
The sale quantity is unclear. (Perhaps 500 units)

FZR250R (3LN7)   1994


Other FZR links
http://fzr250.com/
http://exupbrotherhood1.com/phpbb2/index.php
http://www.fzrarchives.com/index.php
http://www.tourtimemedia.com/fzr/

Quelle