I was replacing the spark plugs on my CBR 650f and when I went to put the boot back in, the ceramic lip broke.

I put everything back together and after riding for 20 min, my bike started misfiring so I know the spark plugs didn’t take.

When I took everything apart again, this particular boot on the damaged ceramic one was pushed out. So my guess is that the broken lip is now causing it not to seal properly

Any suggestions for a fix?

 

Maybe build up the void with JB weld and then file it smooth?

 

The boot on plug lead doesn't seal the cylinder head - that's the job of the washer on the plug itself. The part you broke is the "rocker cover", not the head - the head is below the cover.

Did you find the part which broke off, or did it drop into the cylinder?

 

I like that idea! Someone just mentioned to me about JB weld last night. Might be an option. Thanks for the response!

 

Thanks for explaining the components! I do still have the piece that broke, it’s just hard to get a good angle to put back and I’m not sure if the piece will fit perfectly. Seems like some smaller pieces fell off of it. But it seems like that might be the only option. Appreciate the response!

 

That piece just stops dust and water from getting into the plug hole - it's not structural.

 

that’s good to know! So if the spark plug misfires and that plug pops out, then it’s a spark plug issue, I’d assume?

 

The only way the plug itself can pop out is if it wasn't inserted properly. The plug is threaded into the head and tightened against a sealing washer - it's not clamped down hard, but they don't unscrew and "pop out".

The plug lead can disengage, usually because they are not pushed down far enough, or the top of the plug is worn, or the little threaded top isnt there (and needs to be there)