Spark Plug Tips And Boots

[90GTVert]

I mentioned some time ago that I had trouble with spark plug boots coming off. It is the result of vibration that damages to both the threads on the end of the spark plug and the spark plug boot. I was replacing both plugs and boots on a routine basis because of this.

Removed tip.


NGK 45 Degree 5KΩ Resistor Spark Plug Boot
(Good plug boot, just not working well for my application.)






Damaged threads.


I ordered some 90 degree angle NGK boots instead of 45 degree angle, because they were over $1 cheaper each. When they came in I discovered that they were meant to use the spark plug with the tip on.

NGK 90 Degree 5KΩ Resistor Spark Plug Boot






Normally, using those means the cap will unscrew itself from vibration and the cap and the boot will fall off. I decided to try using a little blue thread locker on the threads of the tip to keep it in place and give these boots a shot.

The snap on NGK boot goes on with authority. It snaps down more securely than the automotive spark plug boots I'm accustomed to. I've put 6-700 miles on one plug and boot and it's still very snug. That's better than the other style would do. The thread locking compound does not appear to be affecting the ignition in any negative way as I had feared it might.

So, if anyone else has trouble with damaged threads and spark plug boots using the original method, you might want to try this.


Decoding Part #s of NGK caps...
www.ngksparkplugs.ca/documents/Resistor%20Covers%20Decoding%20English.pdf

Here's a video of someone replacing these screw-on caps :
www.youtube.com/watch?v=trzMzfcYpO4

[Fox]

Good advice! The NGK caps are the best. I've had one for a couple years and it still holds the plug like it did when new. I got the straight one because that's all the bike shop had. It works okay on my scoot but a lot of other scoots require a 90º or at least a 45º bend. I paid $ 2.79 + tax at an independent MX shop. Cheap mod that really pays off if you ride in the rain. Moisture in the cap is a common problem on the 4 stroke Chinese scoots due to the cooling fan blowing road spray all over the cap.




The boot just unscrews from the end of the wire. Then you just screw the new one on there.

[90GTVert]

Mine's still holding up a month later, and that's saying something. I was going through a couple of plugs and a couple of caps a month. About every 500 miles I'd have to replace one or the other or both. It's been 1000+miles on the same plug and cap now.

EDIT : Much later, still the same cap. The snap on style seems to be working much better for me.