The insulator on the plugs on my center cylinders are bright white (lean plug) while the outside cylinders are tan (normal plug).

Anyone else have this? Or are my #2&3 running as lean as they appear to be?

 

Hey:

Compare to this chart, tells you pretty much what you need to do. Also plugs can only be checked immediately after a high speed final gear run to give complete accurancy, as any other time is not under full load to the same degree, and may be misleading. This should be done after a full tune,(new plugs, Valves checked/adj, and carbs sync'd and balanced, clean air intake/filter), and cooling system verified it is operating correctly, (fan works,thermo open, rad clean, good coolant and no rad obstruction) as this will give the most info on how your engine is running at its peak.

It is not uncommon in inline 4/6s to have to rich/lean carb mains in the center two cylinders, 1-2 steps when on pods as airflow is not evenly distributed to them, some airboxes also have this fault but to a lessor degree hopefully.

I would check out your Carbs sync and balance, then valve adj on center 2 ex, as they may be a little to tight, if carbs check ok, you will also have to resync carbs after any valve adj, hope this helps. In this chart 13-23 is what I want and look for across the engine all to be the same. 23 is my pref at full throttle, top gear, hot wx, race ready engine check. This is because in any other condition its running cooler and just right. Plug should look like new, not glazed.

Spark Plugs

Dub