spark plug heat range

[Greaser Greg]

How does one know when to change from B8HS to B9HS on an R5?  Was running great with stock heads and Spec II Classics on 32.5 pilot, third clip on stock needle and 170 main. Got the heads worked, upped jets to 175 and went up to b9 plug and it's not as fast, with less noticeable power band at 7k. Plugs are dark.  Doesn't a flatter squish band need more gas?

[teazer]

plug color is a measure of how hot the plug got on a particular run. That is affected by load, Air:fuel ratio, compression, pipes and so on. You appear tho have changed a lot of things at once, so it's hard to tell which of them reduced plug temperature.

If you check plugs at part throttle it tells us a little about plug temperature and nothing about jetting.

You said it makes less power when you could reasonably expect it to make more.  Is it really making less power or is it just smoother than it used to be?  A bike that comes on the pipe hard feels powerful even if it makes less power but simply has a bigger hole in the power curve.

If it does in fact make less power it is probably jetted wrong or ignition timing is off. 

Where you read plug temperature as it relates to heat range is the side electrode.  How does that look?