Exhaust Fin Nut loose

OK, I really didn't mean to start a war! Thanks to all of you for some great suggestions. Good news... the threads were not stripped so i was able to retighten. I got it just over hand tight when cold, then warmed it up for about 5 minutes and tightened some more, took a 10 minute ride and while still running, tightened a little more. i was able to use the "C"-spanner from the original tool kit to tighten the fin nut.

Thanks again!

rasandler said:

OK, I really didn't mean to start a war!

Click to expand...

Non of us do, but those are the chances we take when posting here. It seem the simpler the question, the more complex the answer.

Try asking where to get valve stem caps to match your tank color. If your tank is black then, of course, it's fairly straight forward.

sorry for imposing

Biscuit said:

I believe the problem with the tab washers is that they fit rather loose even when locked and though will prevent an exhaust nut from totaly un doing itself, will not stop it from loosening. Once loose the nut can rattle back and forth thereby eating up the threads in the head.

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Yes, but the remedy is this - place the flat tab washer on top of a half inch gap in bench vise. Lay a socket bar on it and give it a tap with a mallet. This puts a bow into the tab washer and as you wind up the header nut, it behaves like a giant spring washer. Warm the engine and heave on the nut with the C spanner. Fold the tabs in and loh and behold...no loose nuts or rattles. Permanent. (This advice is conveniently absent from the factory manual, and thus another source of endless amusement with owning a Commando).

ML said:

Biscuit said:

I believe the problem with the tab washers is that they fit rather loose even when locked and though will prevent an exhaust nut from totaly un doing itself, will not stop it from loosening. Once loose the nut can rattle back and forth thereby eating up the threads in the head.

Click to expand...

Yes, but the remedy is this - place the flat tab washer on top of a half inch gap in bench vise. Lay a socket bar on it and give it a tap with a mallet. This puts a bow into the tab washer and as you wind up the header nut, it behaves like a giant spring washer. Warm the engine and heave on the nut with the C spanner. Fold the tabs in and loh and behold...no loose nuts or rattles. Permanent. (This advice is conveniently absent from the factory manual, and thus another source of endless amusement with owning a Commando).

Click to expand...

The tab washers from AN now come with the bend. I had done the bend when I first put them on my Commando 5 years ago, and showed my Norton guy. He started doing 'the bend' as a matter of course. When AN started sending them that way, he made a point of showing me.

Yes "the bend" helps but those locks still don't provide the kind of tension that lock wire does. I think the problem is the header sealing with the composite gaskets may come loose as the gaskets collapse "like a mini head gasket"and to be honest lock wire probably does not add any real tension to the big nut either but I feel may be better. Of course the best way to assure they are tight is to just check and tighten every once in a while. I have a MK3 with the original pipes along with the split collets and bell shaped seating pieces plus of coarse the latter cast iron nuts. These never had any means to lock themselves on and they only came loose on me once around 1977. Just for shits and giggles now though, they are safety wired around one of their own fins and around an exaust rocker cover nut. (no holes drilled)