Iridium vs oem spark plug

Hello guys, does it improve something to put BR8EIX instead of Br8es plug ?

Anything with an R in the title has a resistor built into the plug. If you already have a resistor in the plug cap it'll result in a crap spark whatever plug you use. 
An iridium plug isn't going going to compensate for a 40 year old engine that isn't factory fresh. 
Whatever plug is recommended by the fsm is what to fit or another manufacturers equivalent of it but definately NOT a resistor plug. 

IMHO, the only thing buying iridium plugs for an older motorcycle will improve is the seller's cash flow.  I'm with Warren, use the fsm recommended plug or equivalent and avoid resistor plugs. Non-resistor NGK B8-ES are getting hard to find.  I've had good luck with Denso W24ES in my Z1.

How do I inow if my cap has a resistor in it ?! And yes I cannot find B8es.. thats why I use Br8es. Does the  Denso W24ES has the same température as oem ?!

I agree with the others about avoiding an additional resistive element into the system.  On some plug caps (never tried with the KZ flavor caps), the resistor can be removed, and replaced with a slug of copper.  

Regarding a resistor plug hurting spark, realize, that some bikes used resistor spark plugs for some specific markets.  Canada   As long as the ignition system is working properly, I don't think a resistor plug is a tragic mistake.

Yes, W24ES is the equivalent to B8-ES.

Resistor Caps; Dynatek 7mm Copper Core Wires:


Denso W27ES-U (corrected) Spark Plugs:



 

Why do you have resistor cap with non resistor spark plug?! I just order 8  Denso w24es-u .. you have w27es ?

 

W27ES-U (correct) is a step cooler plug...   
and one resistor component is recommended per cylinder.

You run coller plugs for what reason?

U-Groove strap feature:


A member suggested that one step cooler plug would provide improved combustion for my engine setup.  

The W27​​​​​ES-U straps have a well defined burn area compared with the W24ES-U shown below:

NAPA sells B8-ES plugs. The new NGK p/n is 2411.
www.napaonline.com/en/p/NGK2411