From Techno Pro Spirit catalogue

[Petrus]

Ultra-light aluminum pulley increases engine response and reduces output loss. Since the pulley diameter is the same as the genuine one, there is no problem even when riding in the city.
With bright green alumite treatment, it is also good for dressing up the engine room.
・ Material: Aluminum
・ For MR-S:
Crank pulley 301g
Idler pulley 165g
Alternator pulley 112g
Water pump pulley 143g

Silly price so no thanks but almost 3 kilo lighter 

[shnazzle]

Ultra-light aluminum pulley increases engine response and reduces output loss. Since the pulley diameter is the same as the genuine one, there is no problem even when riding in the city.
With bright green alumite treatment, it is also good for dressing up the engine room.
・ Material: Aluminum
・ For MR-S:
Crank pulley 301g
Idler pulley 165g
Alternator pulley 112g
Water pump pulley 143g

Silly price so no thanks but almost 3 kilo lighter 

What is the price out of curiosity? That's a lot of weight off the spinning masses. The only thing I don't like is the crankshaft pulley. Hard to see but it doesn't look like it has the damper. That's a no-no for a daily in my opinion

[Petrus]

68000 yen.

The harmonic balancer is a controversial thing. Seems to mé that taking 4-5 kilo off the flywheel affects vibrations /harmonics too and that it revered without structural issues.
According to them, the medium lightened flywheel is best.

The underdrive alternator pulley has the same dark cloud hovering over it in the MR2 community and I lóve it. No electrical issue whatsover even with an 800 gram mini battery, deminishes load on the alternator and it ís noticeable.
On the other hand, the freewheel pulley is hallowed as better then sliced bread whereas it is heavier and .... NOBODY has actually tried it.
The wonders of the virtual world :-)

I have the lightweight VMS crankcase pulley underway. The OEM one is 1660 gram.
I do not do 10k kms/year. This year way less still.

[shnazzle]

Hmm. Don't know enough about it but all I know is don't remove the harmonic" balancer" or "damper".
But it's definitely an attractive weight saving. 
And mucho money-o

[Petrus]

Hmm. Don't know enough about it but all I know is don't remove the harmonic" balancer" or "damper".

The thing works exactly like the weights in rubber stuck in the end of motorcycle handlebars. They work. It is all about comfort though.

Now when one mods the engine with say a free flow exhaust or anything else adding hp or shifting the character like with the MAF mod, the harmonics of the crank change.
Add a turbo and it changes 30 - 50%.
Same thing taking off 50% of the flywheel which is a great balancer and gyroscope even.
Now everybody who ever did anything to the tune of an old motorcycle knows how this affects the vibrations.

Lastly back to the beginning. Harmonic dampers are also about comfort. The same reason why the factory supports the engine in rubber and not in pu.

Imo the crank pulley scare is unwarranted nit picking on óne thing whilst ignoring all else:
With this engine being prone to consume oil ánd that the oil can surge during prolonged hard cornering it is imo more likely that lubrication is the issue in case of a spun bearing.
Improving roadholding, stiffening the tub, adding negative camber, all raising the cornering speed, increasing centrifugal force is imo at least as likely to cause lubrication issues.
I mean, spun bearings have occured without a lightweight pulley fitted. More have occurred with the OEM pulley than with a lightweight one. Even here on the forum. Do we now say that this was because of the pulley?
But .... caveat emptor ofcourse.

[shnazzle]

More worried about vibrations destroying the engine. 
Much like a flywheel (lighter or stock) is balanced to prevent any shaking or vibration, I would expectt the same of this pulley. If that's the case; not a problem.

[Petrus]

More worried about vibrations destroying the engine.

Again; it is all relative. Any modification which affects the bang on the piston affects it too and half the tribe strives to bang as much extra as possible without giving crank balance or vibrations a thought.

The issue the harmonic damper addresses is the torsional vibration only:
https://en.wikipedia.org/wiki/Torsional_vibration

As you can read the primary cause is the bang on the piston and also that the flywheel is quite important.
Also that the crank pulley is a tuned damper; change the bang and or the flywheel weight and it is out of tune:

´Tuned absorber type of "dampers" often referred to as a harmonic dampers or harmonic balancers (even though it technically does not damp or balance the crankshaft). This damper uses a spring element (often rubber in automobile engines) and an inertia ring that is typically tuned to the first torsional natural frequency of the crankshaft. This type of damper reduces the vibration at specific engine speeds when an excitation torque excites the first natural frequency of the crankshaft, but not at other speeds.´

Much like a flywheel (lighter or stock) is balanced to prevent any shaking or vibration, I would expectt the same of this pulley. If that's the case; not a problem.

Again, this pulley is túned damper.  Change the bmep and screw the tune. This why I decided to delete the out of tune weight.
All in all, duties you name it, 100€.
Yes, a lot for a pulley but is for what it dóes and it is 1,2 kg rotational mass delete.

[tom256]

More worried about vibrations destroying the engine.
Much like a flywheel (lighter or stock) is balanced to prevent any shaking or vibration, I would expectt the same of this pulley. If that's the case; not a problem.

I was look for some clues and most people says that modern engines are already balanced inside (like 1ZZ-FED). So replacing crank pulley should not cause more vibration or damage engine in any way.

[shnazzle]

More worried about vibrations destroying the engine.
Much like a flywheel (lighter or stock) is balanced to prevent any shaking or vibration, I would expectt the same of this pulley. If that's the case; not a problem.

I was look for some clues and most people says that modern engines are already balanced inside (like 1ZZ-FED). So replacing crank pulley should not cause more vibration or damage engine in any way.

And yet, a real life example; Carolyn noted a vibration she couldn't trace. Ultimately changed the crank pulley and hey presto, vibration gone. 

Not saying that proves it, but it's enough for me personally in addition to the fact that Toyota put it there. 

Each their own decision

[jonbill]

although most cranks are balanced, the balance weights only balance longitudinal harmonics (on the plane of the crank) a crank pulley damper dampens rotational harmonics (around the crank axis).
however, I believe inline 4 engines rotational harmonic frequency is at revs higher than most operating ranges (maybe 10k rpm).
straight 6s however have it lower down- Nissan L28 cranks snap between 7and 8k rpm without a damper. Early Triumph 6s have it below 6k rpm.

[Petrus]

And yet, a real life example; Carolyn noted a vibration she couldn't trace. Ultimately changed the crank pulley and hey presto, vibration gone.

So? Ergo, it´s there for the comfort of the users as well. As I observed the 1ZZ is very much a general purpose engine used in MÁNY applications.

Not saying that proves it, but it's enough for me personally in addition to the fact that Toyota put it there.

No discussion there.
The ónly point I am trying to make is that changing the thing will not see the crankshaft desintegrate or start spinning bearings like a Thermomix.

Each their own decision

and for that each needs balanced (pun intended) info as you like to point out.