Has anyone had any luck with the very cheap nasty spark plug repair kits like this? http://www.ebay.co.uk/itm/VORLUX-SP...642910&hash=item2125f7d34a:g:AScAAOSws4JW8RgS I've been asked by a friend if I can sort out an off road go kart thing based around a Chinese pit bike engine. First (and maybe the only) problem is that the spark plug threads are stripped. I'm guessing its going to need a bit of care to drill out the existing hole (size unknown at this point) and then to start the tap squarely especially with the head / engine in situ. If it was a more common size / pitch I'd happily spend £30 or so on a better V-coil set with the stepped tap etc but for a such weird thread size of M10 x 1, which I'll likely never use again I'm not sure it's worth it unless the overwhelming consensus says that the £7 kit above is a waste of time.