I had one of my spark plugs stolen yesterday evening. When i changed it out, the bike started backfiring upon deceleration. I did notice that the ones i did have in were NGK and i replaced them with Harley spark plugs. the tops did look different. Could this cause the bike to start backfiring all of a sudden now?

Thanks for any help

Scott

 

Which NGK plugs were they and what Harley plugs did you replace them with?

 

The NGK was DCP7RE and changed it to Harley 6R12

 

They probably took something else or maybe screwed with something else. No one would take a plug unless it was your latest squeeze that you pissed off..

However, did you gap them carefully? If you used the correct Harley plug and the correct (per the aftermarket book) NGK will work fine except NGK throw the spark retard off a little killing a little efficiency since they have a lot more resistance.

On a cruiser, they at one time read the resistance and curved the spark. My 04 does.

Since you do not have a signature line, have not a clue what Sporty you have.
Been making these things for 40 years?

Is it possible that someone mapped it for the NGK?
You really do not need an Iridium Long Life Spark Plug in there.

 

I don't think anything else was taken. I did not gap the plugs just took them out of the box and inserted them. I did speak with a harley mechanice and he said maybe one of the plugs is bad? sorry, the bike is a 2012 Nightster 1200. The harley plugs were recommended to me from the mechanic that is why i use those....do you advise using another spark plug?

Scott

 

The plugs gap at .040. And Sportsters do not have ion sensing like the big twins.. The correct NGK will work the same as a Harley plug. Verified by Boswells Harley in Nashville and Bumpus Harley in Murfreesboro.

 

I guess it's a little late to check for foreign objects in the chamber.... I know I would be paranoid as hell.
One security concern with bikes.... Oil tank, gas tank, now cylinder holes.
What has the world come to. There was a day when someone would scared to death getting caught screwing with a bike.

 

Yeah. I see no reason to steel one plug. There is more to this than we know.

And that's funny Ratwerke , do you know why I pulled you over. I like because you made Ds in school and other than Walmart this is the only place you can get a job. LOL

 

I live in San Francisco and the homeless and drug users take spark plugs to use as crack pipes, happens all the time!!!

 

WOW our homeless and crack heads are not that resourceful.