A friend just phoned me and told me that his Monster 696 spat out its front cylinder spark plug on a straight bit of road yesterday. Apparently, it went off like a rifle shot. Just as well it was the front one; the rear one would likely have gone through him. A local garage said it could only have been caused by the spark plug being torqued down too strongly which cracked the thread in the head, then with the pressure at high revs it blew out. It was also fortunate that the bullet spark plug didn't hit anyone or anything. Dangerous. Anyone ever head of anything similar happening? It's a new one on me. What's the repair - new head or can you tap in a new thread?
not heard of it myself, but you should be able to "helicoil" an new thread in. Helicoil is a brand, IIRC, but is like a toughened spring with an oversize tap to cut a new thread in the hole and then carefully turn the new coil into the hole and ther you have it, a brand new thread. your mechanic will likely be able to sort this for an hour or so of his time. here is one on ebay - 15 Piece Helicoil Thread Repair Kit M14 x 1.5 x 12.4mm Garage Workshop Tool | eBay HTH, Pete
My wife had exactly the same thing happen on a Toyota Avensis years ago. Garage managed to helicoil the head insitue and never had any further probs. I'd never heard of such a thing until then either!
pretty common in the trade as many others will add, I can remember seeing the odd dented car bonnet as a result but far more dangerous on a motorbike (as said)
seen plenty come loose never seen one go off. normally a lot of warning given when a plug comes loose. lots of chuffing.
New head, helicoil the existing head, or retap the head and use an oversize sparkplug of same rating. That is it has destroyed the threads of course. I would want to get the head off and check for exact damage before deciding on the best course of action.
