Spark Plugs

[Claviger]

As part of my most recent round of upgrades, I replaced the DPR7EA-9 plugs with DRP8EA-9 plugs to help prevent detonation with the rather extreme compression my motor has, among some other measures taken. I am not great at reading plugs, but, here are the carefully removed plugs which were in the motor for about 2,000 miles on the 265 build after going to Carpenter and 2,500 miles before the high comp pistons. For those who still have this skill (dark art), what do these tell you?

The area between the ceramic and steel threaded side are free of debris. None of the plugs were wet when removed at all.

I did run some MMT based octane booster through the motor, which, will account for the slightly reddish brown covering the ceramic and on the negative electrode.

 

[BillyIndiana]

Looks a little rich to me. I am no expert.
I will have to pull my plugs in a couple thousand after the mods I have made.
Curious to see what people with more experience with the Rocket say.
This will be a helpful thread. Thanks for posting.

 

[Claviger]

Closer look.

I get a little rich from the face of the ring around the electrode and a little too hot a plug based on the how high up the threads the brown discoloration is. Then indications of a little too much timing based on how close to the weld on the electrode the discoloration line is.

Using this as a guide:

Tuning an Engine by the Spark Plug. The Basics of Reading a Spark Plug.

 

[Ishrub]

I thought old time plug reading was done to plugs after motor kill switch used to stop engine while running with load on road/test strip. The plugs were then removed and 'read' before carby mixture screw adjust and jetting changes to enrich or lean mixture.

 

[Claviger]

That's optimal, and, generally how the bikes parked, run hard uphill full throttle in 2nd gear, coasted 200-300 meters at the top of the hill, into the garage and turned off.

 

[Fenners]

Closer look.

I get a little rich from the face of the ring around the electrode and a little too hot a plug based on the how high up the threads the brown discoloration is. Then indications of a little too much timing based on how close to the weld on the electrode the discoloration line is.

Using this as a guide:

Tuning an Engine by the Spark Plug. The Basics of Reading a Spark Plug.

Hi Claviger, I am not an expert but having read the article, Brian did state to use new plugs for reading. Now your plugs are not new, or I don't think they are based on the 2 left hand ones. I am seeing an off centre spark - look at how the strap is over bent towards the electrode and the electrode tip is not square (could be losing some opph there).
The soot or carbon deposit is black - on the thread and ring - therefore I agree running rich (however you did run at full throttle before cutting off)
The electrode looks cleaner than the ring and thread but that could be from the overheating and MMT

That my reading