Changing to Hotter Spark Plugs

Bike (Z1) has been running OK, it has a 4 into one (Kerker) exhaust.

I thought I would try some NGK B7ES, one heat range "hotter" than the usual NGK B8ES.
The bike has been running Ok, i thought I would change the plugs purely as an experiment.

Everything seemed good, except after a short ride of about 20 km's, I noticed the exhaust had blued/ brown (straw) up on all of the header pipes.
Anyone know the logic behind this?
My main query is..... Could changing to hotter plus given rise to this sudden "blueing?

RegardZ.

Do the center electrode appear white in color? Are you seeing Aluminum on it too? If so, go back to the B8ES before doing engine damage....

Garn wrote: Bike (Z1) has been running OK, it has a 4 into one (Kerker) exhaust.

I thought I would try some NGK B7ES, one heat range "hotter" than the usual NGK B8ES.
The bike has been running Ok, i thought I would change the plugs purely as an experiment.

Everything seemed good, except after a short ride of about 20 km's, I noticed the exhaust had blued/ brown (straw) up on all of the header pipes.
Anyone know the logic behind this?
My main query is..... Could changing to hotter plus given rise to this sudden "blueing?

RegardZ.

Anyone know the logic behind this? -- engine is running too hot.

My main query is..... Could changing to hotter plus given rise to this sudden "blueing? -- Yes.

Good Fortune!

Hotter plugs run hotter.
They don't shed heat to the surrounding material as quick so will create a hot spot and raise the cylinder temp.
This will cause the blueing due to excess cylinder heat and will cause engine damage, holed pistons,heat seizure etc.
Change to colder plugs ASAP.

Thanks guys, I guess i'll change them back to "8's" .... Possibly try going the other way with NGK-B9ES.
The centre electrode is steel looking tending to light brown, the outer peripheral of the plug was black.
RegardZ.

Put the plug's Maw Kaw did and fix your carb. jetting.

There is something important to tell this forum.. ZukDave has a point...
Changed back to B8SE, went for a ride...... Still Bluing.
Pulled down carbs, I found the bluest pipe had a blocked pilot jet (17.5), others were semi blocked too.
Checked main and increased main jet size to 113 from 107.5. Not bluing anymore, however, hesitant at low speed when giving it a hand-full.