Exhaust Fin Nut loose

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rasandler

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I just went out to start my bike ('73 850 roadster) and once started, noticed that the fin nut was loose and there was a little smoke coming from there. is this a sign that the gasket needs to be replaced or just that the washer needs to be retightened? to tighten it do i just bend out the tab on the tab washer, tighten the nut, and bend the tab washer back? or is there more to it?

thanks guys!
 
rasandler said:
I just went out to start my bike ('73 850 roadster) and once started, noticed that the fin nut was loose and there was a little smoke coming from there. is this a sign that the gasket needs to be replaced or just that the washer needs to be retightened? to tighten it do i just bend out the tab on the tab washer, tighten the nut, and bend the tab washer back? or is there more to it?

thanks guys!
Click to expand...


Be very careful with it. Check to see if your exhaust threads in the head are stripped or getting that way. Fairly common problem. I sent my head out to have inserts done on both sides, then got a set of 750 style nuts. They are a few threads deeper than the 850's. Also did away with the tab washers.
 
Once you verify the threads are OK and tighten the nut you can prevent it from loosening again by drilling a hole in a nut fin and a nearby head fin and safety wire them together...did this to my bike a few years ago and have had no further trouble with them loosening....this way it is also possible to check that they are still tight, sometimes they need to be retorqued a time or two (of course if the nut does tighten more the safety wire will need to be replaced)

edit- I meant safety wire from exhaust nut to rocker cover nut, NOT head fin
 
rasandler said:
to tighten it do i just bend out the tab on the tab washer, tighten the nut, and bend the tab washer back? or is there more to it?
Click to expand...

Do it when the engine has fully warmed up, preferably while the engine is still running as there's less chance of it loosening off again than if it is tightened cold.
 
NEVER NEVER NEVER safety wire anything through a head fin!!! when the stainless steel wire vibrates in the head it WILL act as a hacksaw.

bluto said:
you can prevent it from loosening again by drilling a hole in a nut fin and a nearby head fin and safety wire them together...
Click to expand...
 
I use the L.A.B. recommended method of tightening the nuts, bring engine up to full operating temperature, then re-tightening while the engine is still running - never have problems with loose nuts - I have 750 style nuts in an 850 head,
Dave
 
bill said:
NEVER NEVER NEVER safety wire anything through a head fin!!! when the stainless steel wire vibrates in the head it WILL act as a hacksaw.

bluto said:
you can prevent it from loosening again by drilling a hole in a nut fin and a nearby head fin and safety wire them together...
Click to expand...
Click to expand...

sorry, I stand corrected...I meant to say to safety wire to a rocker cover nut, not head fin
 
is it ok to disagree?

I have safety wired my exhaust nuts to the adjacent head fin for 38 years now on six different Commandos

none of the fins have been "damaged" or "sawed through", in fact that little hole is STILL the same size

and I have never had a nut loosen because after tightened securely and properly, the safety wire is just "insurance"

and no, it ain't hurting a damn thing to do it because it's a Good Thing


ready to be attacked by the Old Wives......
 
There's no need to drill a hole in a fin for this purpose though, as noted, it's been done for at least as long as there have been Commandos and probably way before then. I wouldn't worry about using a hole in a fin for safety wire BUT I wouldn't drill one either. If there's already one there from a PO, use it if you want; if not, use the rocker cover stud/nut for the safety wire.
 
Windy (bill) safety-wired my exhaust nuts back in 2008...11K miles and approx. 5 years later still tight as ever.....looks cool, too IMHO.
 
I use a long extension when it's warm. Just don't over do it. Make sure your threads are good to start. You guys with the down pipes have it easy. I have to dick around trying to keep things lined up when I tighten mine. I use wood spacers between things while tightening. Never used any safety wire and it's been good for me, but I've not that much experience except with the one I have. I do keep a thick punch and something heavy to hammer with just in case.

Dave
69S
 
OK...this is more fun than a dog pile! And no I don't mean the kind you step in on the sidewalk. Here is my method...put a little high temp silicone on the threads, run it in, run the bike up to about 4000 RPM and tighten that sucker down! Then if you feel you must safety wire it, go from 2 o'clock on the right (left side facing from the front) nut to 8 o'clock on the other nut. Then if one loosens it tries to tighten its partner.

OK, flame on!
 
1up3down said:
is it ok to disagree?

I have safety wired my exhaust nuts to the adjacent head fin for 38 years now on six different Commandos

none of the fins have been "damaged" or "sawed through", in fact that little hole is STILL the same size

and I have never had a nut loosen because after tightened securely and properly, the safety wire is just "insurance"

and no, it ain't hurting a damn thing to do it because it's a Good Thing


ready to be attacked by the Old Wives......
Click to expand...



hmm, well I'm now completely convinced that works OK and now stand uncorrected (and miscorrected prior to that ;-)...
 
I believe the most effective and invisable solution is
use 850 exhaust nuts and in the thick fin on the exhaust nut drill and tap hole suitable for a grub screw
tighten exhaust nut when engine hot then proceed to tighten grub screw on to exhaust header pipe
exhaust nuts stay tight and easy to remove when needed
 
I use nickel neverseize and an aluminium / asbestos suzuki gasket.

Lube the thread and tighten like a spark plug (until you feel the gasket crush) with a short bar (12"). Get it hot and nip it again.

Every time you come back from a long ride nip it up with a short bar and 1 hand. After about 6 times you wont get any more so forget it. No tabs or lock wire.

I did this on 2 Commandos 8 years ago. 1 x 750 and 1 x 850 and a few since. Never had an issue.

I think over tightening is the cause of the loosening.
 
Nortiboy, +1

I agree with everything you said. Use anti-seize, tighten when hot (running isn't a bad idea), skip the tabs and wire. I add this to it:

Spring for one of these.
http://www.oldbritts.com/19_063968.html

Get the bronze 750 finned exhaust nuts if you're not using a crossover. They're bronze, take a stainless steel brush to them. They look very cool and they expand and contract at a rate much closer to Aluminum than the steel 850 version.

http://www.oldbritts.com/16_062464.html
exhaust-nuts-850-750-t1070.html
 
So what exactly is wrong with the tab washers? I've been using them for several years and have no problems. They seem like the logical solution. No drilling etc.
 
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. Safety wire will put a strain on the nut in a clock wise direction that in theory will try to tighten the nut. No matter what you use or don't use, KEEP YOUR NUTS TIGHT!
 
Someone asked if I had a picture of my safety wiring suggestion. I don't, as I must confess, I didn't safety wire my nuts! (for the record I said "if you must...")

Here is a diagram of how it would look viewing the front of the head. The black circles are the nuts, the red line represents the wire. It is common for a lot of things to be wired in this fashion so that any member of a group that tries to back off tightens a partner. If you try to turn either nut counter clockwise, the other nut is forced to rotate clockwise. Obviously you would want things snugged up well before applying the wire.

Exhaust Fin Nut loose
 
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