TOPIC:

I'm just going through all the wiring on the bike and fixing what looks to be iffy. Last night took a look at the spark plugs and noticed that the plug caps (i.e. boots) were not really on the spark plug very tight. You could easily wobble them around on top of the plug. I'm assuming this is not normal. I'm not used to motorcycle plugs, but on the cars I've worked on they sort of snap on and don't move. It would seem to me that the connection wouldn't be very good, especially on bumpy roads.

The plug I'm using is NGK B8ES and the code on the plug cap is LB05F. According to the guide on Z1 Enterprises site this looks like the correct combination. Is there something I'm missing? Is the cap supposed to move around like this. I only bought the bike just before winter so I never really rode it to notice any issues.

BTW this is on a 1978 KZ650 D1.

Thanks

Just looking at the plug, am I supposed to unscrew the cap at the top to expose the threaded part?

Depends on the spark plug caps, as far as if you need to remove the little threaded tops. I would say no, you don't need to remove them. Mine are still on.
The spark plug caps do have a bit of movement to them when there on. You want to feel a good snap to them when you press them on. If they come off and on too easy, maybe the inner part of the caps need to be squeezed together a little.

If you have the original spark plug caps then yes, the little brass bits screwed onto the top of the spark plugs should be removed. As you push the spark plug caps on the threaded end of the plugs you can actually feel them grabbing the threads on the plug. This is how my '77 KZ650C1 was shipped from the factory and the spark plug caps have always been very tight, in fact, they're hard to pull off the plugs. The original sparks plug caps are made of a hard plastic or bakelite type material. I don't think there's a way to "squeeze" the connectors inside them. If yours have been replaced with some aftermarket product that doesn't work well, you may want to get something closer to the original. NGK makes some that are similar to original. Ed

Thanks rstnick. My cap won't go on over the terminal at all with the top on. The only thing keeping the cap on the plug is the rubber boot. It seems the terminal is too big to fit in the receptacle in the cap. I removed the top and it fits nice and snug now. Is it alright to use like this? Or am I using the wrong spark plug cap?

Thanks Ed, you must have replyed as I was writing my response to rstnick. I'm not really sure if they are the original caps or not. I just picked up the bike before the winter and don't really know the history. They are the hard plastic type though and it looks as if the receptacle in the cap is too small to fit the top of the plug. So I unscrewed the tops and they now fit really nice. I think I'll try them like this and see how it goes. Will have to wait a while though as bike won't be ready for a month or more.

Thanks for your help.

Yeah, I have aftermarket caps. Sounds like you need to remove the little screw on tops from the plugs.
Keep them just in case.

Will do, thanks again.

I agree with Ed, Remove the tops of the plugs.