Spark plug???

[rich dupont]

I own a 2005 rocket3.. with 18500 miles.and my big question is.. when do you change the spark plugs? What are the symptoms if you have one bad plug..knowing that you have two per cylinder??

 

[Gregger]

Pretty hard to determine if a plug is failing on the Rocket without using an oscilloscope given the fact that you have 2 plugs per cylinder. Most of us don't own them. Without the scope, the only real way is to pull the plugs on the suspect cylinder and compare the two (or the complete set). Check the color of the plugs for consistency. You could also remove the plugs, hook them up to the coil wires, ground them out and spin the engine over to see if there is spark. From my experience, spark plugs today rarely fail unless they are fouled with oil, fuel or carbon.

One symptom that will cause a misfire at around the mileage you have is a loosening of the 2 primary wire terminals going to each of the 3 coils. It is a known problem. Remove the wires and slightly crimp the female terminals for a tight fit. The only issue is that the front coil can be a real pain to get too

 

[TURBO200R4]

I own a 2005 rocket3.. with 18500 miles.and my big question is.. when do you change the spark plugs? What are the symptoms if you have one bad plug..knowing that you have two per cylinder??

I changed mine at 50,000 and installed ones with 25,000 that looked like new
Hth

 

[Journeyman]

Pretty hard to determine if a plug is failing on the Rocket without using an oscilloscope given the fact that you have 2 plugs per cylinder. Most of us don't own them. Without the scope, the only real way is to pull the plugs on the suspect cylinder and compare the two (or the complete set). Check the color of the plugs for consistency. You could also remove the plugs, hook them up to the coil wires, ground them out and spin the engine over to see if there is spark. From my experience, spark plugs today rarely fail unless they are fouled with oil, fuel or carbon.

One symptom that will cause a misfire at around the mileage you have is a loosening of the 2 primary wire terminals going to each of the 3 coils. It is a known problem. Remove the wires and slightly crimp the female terminals for a tight fit. The only issue is that the front coil can be a real pain to get too

+1 on what @Gregger said about the coil wires- very common and not a one time fix.

You may not know that the service manual is in the Resources section in the header above....