I use a NGK DR8ES-L (I think, not at home to check right now) in my quad. It is the stock plug that is recommended by Honda. Anywho, I never really paid attention to it but is there supposed to be a "top" to it? I have changed it a couple of times and all of the ones I have bought have never had the little thing (resistor??) that is supposed to screw onto the top of the plug. There are threads for it, just no part in box. The plug that was in there when I bought the quad (used) was that way as well, so like I said, I never really questioned it. It seems to run great without it. Only thing I notice is that when I take the plug out the top is bent slightly. I have changed the plugs on cars, and those usually have the little thing in the package seperatly and you have to screw it on yourself.

Thanks

 

No cap. The plug wire grabs the threads.