I was complaining in a previous post about the Yamahaha backfiring on a closed throttle. The first thing to suspect here is a leak in the exhaust somewhere, allowing oxygen in to mix with unburnt fuel and create a minor explosion. As the exhaust headers are rusty and ready for the bin, I suspected a pinhole in one of them. Today, as an experiment, I bought some exhaust bandage and wrapped them tightly (cheaper than a new exhaust by a factor of about 20). Sadly, it has made no difference. I then wondered if the exhaust gaskets had started leaking, so I tried to undo the bolts that hold the exhaust clamps on, to get in there and have a look (and slap them up with a bit of exhaust paste if necessary). I have planned to get some stainless steel headers in any case - the headers are awful, and the stainless ones look fab, as well as being everlasting - so I would have to take these clamps off at some point.
The first one turned with that bending-toffee feeling that should have warned me. The next thing, I have the bolt, and part of the stud, in my hand, and the rest of the stud still firmly in the cylinder head.
Assuming the rest will be equally rusted in place and weakened, I'm not going to try the others. It looks like the cylinder head will have to come off, so that I can use the appliance of science (i.e. a workbench, some heat, and some serious toolery) to get the other three to comply with my wishes. I might as well order the new headers and do it all at once.
As I said, bollocks. That means the XT will be off the road for at least a week, and I will be commuting on the Pan, which is not the ideal tool, in the same way that a 747 is not the ideal tool for gliding lessons.
However, the Pan sailed through its MoT this morning with just an advisory on the front fork seals, so it's not been all bad today.