Hi everyone,

I have a beat up '98 CBR F3 that I'm attempting to fix up. Things have been going well, and today I changed the plugs. When I got to the #4 plug, I saw something alarming, which is that there appears to be two sets of threads on the plug, one set larger than the other. Here is a picture (sorry for the quality):

imgur: the simple image sharer

When I tried screwing the new NGK into this hole, it seated after a small number of turns, as if it was only screwing into the threads at the top of the plug in the picture, which correspond to the normal threads for the plugs. The larger threads are bigger than normal.

I should mention that the spark plug came out with a completely normal amount of force, and nothing seemed out of the ordinary until I looked at it.

Did this plug rip out the threads in the engine? What are my options in this situation? Can I screw the new plug into the remaining threads and hope for the best? Thank you in advance to any insight anyone can offer into this problem...

Ricky

 

That is an improperly installed timesert. Usually they get loctited in. Try to unscrew it off the plug and put it on the new one. Screw it back in and hope for the best. If you have some loctite, put a dab on the threads that touch the head, not the plug to tinesert threads.

 

Thank you for your prompt and informative reply, my friend! I really was clueless as to what the hell was going on there. I'll try it and update with the result. Sadly "hope for the best" is probably inevitable with something like this.

 

I used Loctite to fasten a nut onto the large set of threads, and then screwed it off using the nut. I got it screwed onto the new plug. When I put it into the engine, it still felt like it seated after only a couple turns. I used Loctite on the outside of the large threads to hopefully bind it to the engine block. I'm going to try to unscrew the plug and see what's going on tomorrow, but I don't really feel confident with it seating so quickly like that.