Hi Dave,

it seems you may have already fixed it! But, it may come loose with the heat cycling and vibration. Another method I’ve used for such temp fixes is as follows:

Take the bolt and drill down from the head end to within 1/8″ of the bolt end, in effect creating a hollow bolt from the head end. Now tap this a suitable size, in your case perhaps 3/32″ or 1/8″, or M3 for the young guns. Now cut a slot into the bolt as you have done from the threaded end to 3/4 the way to the head clamping face.

Wind the bolt into the hole as far as it will go and it has a slight grip, now wind a second bolt or grub screw down the centre of the first bolt. This will seat into the drill point / thread blind end and spread the bolt from the bottom into the hole. You can tweak the outer bolt tighter as you tighten the grub screw, and this method does not risk cracking the casting as you cannot put too much pressure on it, and it will come out easily by loosening the grub screw.

If you current fix works then leave it, otherwise perhaps try the above, either are easier than stripping half the bike!

Cheers,
Rich

I’m sure your’s will last a while, I’ve told myself about fixing things properly that are still running on my bikes today, on the “to do” list. Its just the barrels are made from grey iron and it is brittle (and soft) so you have to be careful winding tight bolts into holes or it may crack. I’ve done this on a head stud last year but luckily it was one of the centre ones so had a decent area around it to seal. It is still together and still water tight today thanks to some good sealer but really I need to take it apart and weld it. Over winter… maybe….

Cheers,
Rich

Hi again.
Another way to approach this problem is to see if there are any “unused” threads left in the bottom of the threaded hole in the block, ie. you may be able to use a longer bolt….Check the depth of the hole and compare that distance with the amount of bolt that projects beyond the exhaust flange and gasket. Get a new bolt and cut it to the maximum possible length, but of course ensure that it cannot “bottom” in the hole. Also ensure that there is no debris in the bottom of the hole. There is often a surprising amount! Whilst on the subject, next time you have the barrel off also check that the threaded holes for the cylinder holding-down bolts are also thoroughly cleaned out, as they also seem to accumulate debris. Yet another approach, ie. bodge, if you have a set of adjustable split dies, is to make a new bolt that is “fat on the threads”, ie. a bit oversize, but don’t overdo it as if too tight it could crack the cast iron if forced in. Make sure that it can be screwed in without resorting to much more than fingers!