The Honda PCX / Forza / ADV150 / SH Forums

Hi all,
hope someone has experience with the below and provide some guidance.
I removed the old spark plug to replace it, and in doing it, I noticed it was very hard and I had to kind of force it to come out. Problem is that the new spark plug now does not screw in, at least on my attempts so far. I suspect a problem of stripped threads in the hole where the spark plug goes. Will try again with better tools...but not very optimistic. Anyone dealt with this before on their pcx?
Thanks!

It sounds like the last installer cross-threaded the plug going in. I don't know what your options are other than taking things apart, drilling out the old threads and installing a heli-coil replacement thread. Maybe you could retap and clean up the existing threads? I'm not sure how you can do that without dis-assembly - the little metal bits will get into the piston where I'm sure they are not wanted. Maybe somebody clever will have a better idea. Good luck.

BTW - where are you? It may have some bearing on the repair parts available to you.

GeorgeSK wrote:It sounds like the last installer cross-threaded the plug going in. I don't know what your options are other than taking things apart, drilling out the old threads and installing a heli-coil replacement thread. Maybe you could retap and clean up the existing threads? I'm not sure how you can do that without dis-assembly - the little metal bits will get into the piston where I'm sure they are not wanted. Maybe somebody clever will have a better idea. Good luck.

BTW - where are you? It may have some bearing on the repair parts available to you.

It does sound like it is stripped and dismantling and helicoiling is necessary.

Did you notice any telltale swarf on the plug threads?

You can get away with dismantling the head if you use a couple of greased tampons under the spark plug hole

Homie might faint after reading that.

Heli-coil was the first solution made for this and it's name has become accepted as the norm. But the "Timesert" alternative has advantages .... check them out and compare.

http://www.timesert.com

If you don'y want to remove the head, some people first stuff the cylinder thru the spark plug hole with nylon cord soaked with grease and then afterwards use a small needle nose pliers to pull it out along with any metal residue that remains. Not recommending this, just saying its a choice. I'd suspect the piston should be at BDC (Bottom Dead Center) to give the tap room to completely thread. But I only know this grease deal being done on vintage stuff, I don't know what the grease left in the cylinder would do to the PCX exhaust sensors & catalyst, etc when the engine is started. Maybe best to do it dry or with a light coat of oil instead..

You can minimize the residue by backing out and cleaning the tap often as you go instead of just driving it thru. Then clean the thread with Q-tips or a piece of cloth before inserting either the helical or timesert.

BTW, its good practice to NOT use a tool to start threading a spark plug, just use your fingers to get it started to prevent a cross thread and then use a tool to torque it up. Also not for the helical or timseert - but DO use anti-sieze on any spark plug or bolt that is inserted into alloy - or anytime stainless hardware is used (some stainless is famous for galling).

Removing the head to perform the tap is clearly the best option but may be a hassle. Your choice!

.

As to the cause of the ruined threads - another likely possibility is from overtightening that little plug.....often from relying on a cheap torque wrench.
Often plug installation instructions avoid this possibility by advising mechanic to give only 1/8 to 1/4 more turning once crush washer is in firm contact with the engine.
Too easy to strip threads with anything but a very well calibrated, expensive, small torque wrench - which few of us own.
My bet is on an overtightened plug.
Nevertheless, a bummer.
Fish

As stated above, check your spark plug for telltale signs of threads cross tracking . (cross threaded) and compare to your new plug.Chances are the original installer over torqued the plug hence stretching the threads making it impossible to reinstall a new plug. You can try a thread chaser tool..See above comments.. Good luck

NGK CPR7EA has 10mm x 1 x 5/8" threads. Insert repair kit is available on ebay. But head has to be removed first.

Thanks all for the help. I am contacting some shops around here for estimates and see how it goes. Will keep you posted.

sergior wrote:Thanks all for the help. I am contacting some shops around here for estimates and see how it goes. Will keep you posted.

Yes, please do.