Do not pre judge untill you measure smoke ring. This next info is for discussion only.
Sometimes a dark porclean is to cold of plug. Example. This is fact bassed on plug choped done at dune. There was an odyssey that we done chops on that was bored,water cooled head and the addition of a cooling fan. The owner jetted it to the understanding that go fat untill stumbles and then drop one. This is the normial procedure. Now with that in mind we did some chops. The results showes a little fat but had a lot of black soot on the porclen( his ngk 8 plug). Upon his rebuild he stated thee was a lot of carbor build up on the exhasut port. Why is there build up if the jetting is right. Two reasons possable. #1 too cold of plug #2 trans oil in the cylinder. So we tested first with a new 8 plug which resulted in a ok smoke ring with build up. Then we tested a 7 which resulted in very close to ok but lean with the build up gone. A simple neddle adjustment would bring the main into line. The reason I believe it had the build up was due to over cooling caused by the fan on the water cooled head wicking to much heat from the cylinder lowering cylinder temp and not burnig the plug clean. This machine did not have any thermo switch to control expansion rate taking heat fromthe collent. One could unplug fan to check but time did not permit. The throttle responce did improve due the total combustion of the mixture allowing a broder prower stroke which could be felt by the seat of the pants.
Please do not go hotter on heat range without checking. On the plug chop if it was to hot it would have shown signs of spotting on the porclean which is why you cut it up and measure smoke ring as well as examine the porclean. On key thing to rember is always gap the plugs the same prior to runs. In this example it required a gap of .045 to get proper gap spark.
Rember when in dout use mfg recomedations and it better to foul one than burn up a top end. If you use the .080 and tan porclean besure to run the mix the same and all filters are clean and you use same octane levles. Better to play it safe and be a little fat than lean. However if you alter the set up in any way you must do plug chop to get it right and achieve max preformance.
Can't wait to see you pics and read your post. Be sure to take notes. what octane ,what mix, filter clean, cranking compression, altatiude, ect. it willhelp later if theres a problem. Oh ya have fun while doing it.
