One down to Sheldon Brown. Thanks Sheldon, your pain is my gain. You've saved me twenty quid today, if it all works out OK.
I picked up a single 6mm tap at an old fashioned hardware store in nearby Abingdon, ensuring the right fit by taking the offending bike part in with me. The tap was £4 the handle £12. I'd seen handles on eBay for a fiver so I passed on that and when I got home a pair of locking pliers seemed to do the trick.
This is not best practice but a ghostly presence, let's call it 'Old Pete', took hold and before I knew it I was half way in, making reverse turns every so often to break up the swarf and clean the cutting faces of the tool, just like Sheldon said. The photo speaks for itself, a nice shiny new thread clearly visible where earlier there was just a stripped out hole. Happy with this.
I was so concentrating on making the right decisions in the shop that I forgot to ask for a 6mm bolt to go with, so I'm not quite finished. There something else though; a thread will strip out when a bolt is overtightened but the clutch lever has always been a bit loose, which is a bit of a mystery. I've tried to tighten it and it sort of worked but then it didn't.
Getting down to the tapping process, I noticed the shell of the lever mounting was overly concave, by this I mean that the threaded faces would not sit flat on the workbench if I turned the piece over. So the assembly really needs to be shimmed out before it's tightened down. Tightening the shell with the ends already meeting would strip the thread and not sort out the slippage. I think this is the root of the problem.
And, although I'd made up my mind not to mention this, of course, as anyone who has read Zen and the Art of Motorcycle Maintenance knows, the best shims are made out of old soft drink cans - a pliable, sticky metal. There, I've said it, now if we can all just forget about Pirsig, it's my blog and it's all about me, OK.
