Exhaust system replacement 1973 750 Commando

Q

quawk

Joined
Jan 1, 2024
Messages
314
Country flag
Have purchased and will be installing my new exhaust system, ie: new header pipes, seals/gaskets, peashooter mufflers, and clamps, (thanks Greg Marsh), to replace the aftermarket exhaust system with turnout mufflers installed by the PO on my 1973 750 Hi-Rider. Seems like I've read in a past thread it's recommended to start the bike and warm it up before attempting to loosen the finned retaining nuts at the cylinder head. Is this correct and do you fully warm it up to normal operating temp before loosening the finned retaining nuts?
 
If the Exh. nuts won't come loose under normal temps. you can try a warm up and see it that helps. The warm up/heat may give you a leg up on gaining some expansion in rusted, tight or overtightened threaded fitting.
Spraying some type of break-free or solvent into the threaded area and letting it soak in can work as well without warm up. If you do heat the engine up it takes a while for the parts to get cool enough to handle. Maybe try some welding gloves but sooner or later you will get bit.
I say all this assuming you have the exhaust nut wrench pictured.
If you are whacking away at the fins on the E nuts in an attempt to loosen them sooner or later one will bend or break. My kids gifted me that wrench as a BD gift and I am glad I put it on my list, right tool for the job and all that.

1716673518796.png
 
Lineslinger said:
I say all this assuming you have the exhaust nut wrench pictured.
If you are whacking away at the fins on the E nuts in an attempt to loosen them sooner or later one will bend or break. My kids gifted me that wrench as a BD gift and I am glad I put it on my list, right tool for the job and all that.

1716673518796.png
Click to expand...
Where would be a good source to purchase the E nut wrench you mentioned and in the pic?
 
quawk said:
Where would be a good source to purchase the E nut wrench you mentioned and in the pic?
Click to expand...
Quawk,
They are readily available at most British bike supply shops.A definite choice for your tool box
Mike
 
Note it is still possible to bend/break fins using the tool shown earlier. Best to engage it only on the thick lobe of the collar, not on any of the fins. Earlier commandos had three thick lobes to engage with, later ones only a single...which can make it next to impossible to engage tool on the lobe where it can still be levered tight. RGM do sell a better tool with a number of slots to engage several fins at same time, thus preventing bending.
 
quawk said:
Where would be a good source to purchase the E nut wrench you mentioned and in the pic?
Click to expand...
Wish I had known you didn't have one! Most sell them for a lot. I have them but the shipping is almost as much as the wrench! Email me. I list them for $19.70 on my web site but as you know, Access Norton members always pay at least a little bit less. The ones I have are 06.3968 from AN.
 
Generally, with the wrench, the nuts will come loose without problem.

When installing I use a tiny bit of Nickel Anit-Seize on the threads. This will allow about 1/4 to 1/2 turn more. I damned near pick up the bike tightening the nuts when cold and then I do it again when at full temp. It's very uncommon for them to come loose then.

In case you don't know, having those exhaust nuts come loose while riding and not noticing it = misery and expense!
 
marshg246 said:
Generally, with the wrench, the nuts will come loose without problem.

When installing I use a tiny bit of Nickel Anit-Seize on the threads. This will allow about 1/4 to 1/2 turn more. I damned near pick up the bike tightening the nuts when cold and then I do it again when at full temp. It's very uncommon for them to come loose then.

In case you don't know, having those exhaust nuts come loose while riding and not noticing it = misery and expense!
Click to expand...
I should have mentioned that I also wire lock the nuts and have an extra exhaust pipe attachment on the front engine Mounting which eliminates the movement that causes the nut to both undo and damage the thread.
 
I said this in the other thread but I just use high temp RTV on the threads and crush gasket. Never had the headers leak, damage a thread or come loose for maybe 30 years now. And I have balance pipes. Which are the difficult ones.

I do use lockwire on the race bike but they never back off.

Like this stuff

www.supercheapauto.co.nz

Permatex High-Temp RTV Silicone Gasket Maker - Red, 85g

Permatex High-Temp RTV Silicone Gasket Maker - Red, 85g
www.supercheapauto.co.nz www.supercheapauto.co.nz
 
marshg246 said:
Wish I had known you didn't have one! Most sell them for a lot. I have them but the shipping is almost as much as the wrench! Email me. I list them for $19.70 on my web site but as you know, Access Norton members always pay at least a little bit less. The ones I have are 06.3968 from AN.
Click to expand...
Thanks for the offer, but I went ahead and purchased one from an Ebay vendor and it seems to be pretty beefy and good quality.
 
johnm said:
I said this in the other thread but I just use high temp RTV on the threads and crush gasket. Never had the headers leak, damage a thread or come loose for maybe 30 years now. And I have balance pipes. Which are the difficult ones.

I do use lockwire on the race bike but they never back off.

Like this stuff

www.supercheapauto.co.nz

Permatex High-Temp RTV Silicone Gasket Maker - Red, 85g

Permatex High-Temp RTV Silicone Gasket Maker - Red, 85g
www.supercheapauto.co.nz www.supercheapauto.co.nz
Click to expand...
I know just starting my bike a couple of times in my shop doesn't really test the "E" nut as to whether or not they'll loosen up, but for now they seem to be sealing. If I encounter loosening at some point down the line, I may consider using the hi-temp RTV as you suggest. Thanks.
 
Tried all the usual stuff - sealants , new lock rings , safety wire , blah ,blah blah . Loosening problem solved with a very simple solution . Bronze exhaust roses re tightened three times over three heat cycles . Two years now and no rattle .
 
Q: Do you need to safety wire everything?

A. NO, only on the parts you wish to keep. ;)

I'm a safety wire fan for those nuts (as well as several others). Some people drill a hole in a fin for the wire but that's not necessary, just loop it around the lower nut on the exhaust valve adjustment cap and twist/tighten.
 
MexicoMike said:
Q: Do you need to safety wire everything?

A. NO, only on the parts you wish to keep. ;)

I'm a safety wire fan for those nuts (as well as several others). Some people drill a hole in a fin for the wire but that's not necessary, just loop it around the lower nut on the exhaust valve adjustment cap and twist/tighten.
Click to expand...
Safety wire is dangerously close to an oil or tab washer thread :)

I safety wire only what Norton did. But then I use Nylock nuts wherever possible, so things don't fall off.

Funniest safety wire thing ever: Working on a customer bike. The PO of the bike "safety wired" the gearbox oil level plug. He drilled a hole in it, installed it, put in safety wire and twisted it. It connected to nothing. I guess he thought it good not to be able to get a wrench on it so it would not be removed!
 
marshg246 said:
Safety wire is dangerously close to an oil or tab washer thread :)

I safety wire only what Norton did. But then I use Nylock nuts wherever possible, so things don't fall off.

Funniest safety wire thing ever: Working on a customer bike. The PO of the bike "safety wired" the gearbox oil level plug. He drilled a hole in it, installed it, put in safety wire and twisted it. It connected to nothing. I guess he thought it good not to be able to get a wrench on it so it would not be removed!
Click to expand...
I must be doing something wrong. Apart from the rear indicator stalks I have never had anything vibrate off a Commando.

Lockwired lots of race bikes but struggling to remember anything falling off them either.

One of the reasons I like the high temp RTV is it forms a secure seal but is also smooth enough to be easily undone. Once I started using it the race bike exhausts never moved or leaked.
 
I said it a few times before, and will say it again:
Tighten the rose nuts with RUNNING engine.
Rev it at 4000 rpm while applying pressure on the wrench.
No need for rubber mallets or excessive force.
Let the vibrations work for you.
Try it, and see how easy the nut turns.

Ever wondered why your 'tight' nuts can vibrate loose in no time? :
 
Last edited:
johnm said:
One of the reasons I like the high temp RTV is it forms a secure seal but is also smooth enough to be easily undone. Once I started using it the race bike exhausts never moved or leaked.
Click to expand...
I have nothing against your solution other than it is good for 650F intermittent which seems low for exhaust.

But I found that a little Nickel anti-seize (2400F) lets me get the nuts much tighter and that they never come loose that way.
 
marshg246 said:
I have nothing against your solution other than it is good for 650F intermittent which seems low for exhaust.

But I found that a little Nickel anti-seize (2400F) lets me get the nuts much tighter and that they never come loose that way.
Click to expand...

Ah well I guess we both found solutions that work for us. Temperature doesn't seem to be a problem on my bike but good to have alternatives.
 

Similar threads

yooper trooper
Rear tire sizes for a 1973 750 Commando.
2 3
Replies
42
Views
3,390
concours
concours
T
  • Locked
1973 750 commando rear brake drum
Replies
3
Views
828
L.A.B.
L.A.B.
D
  • Locked
1973 750 commando roadster Combat Engine parts?
Replies
2
Views
907
Ron L
Ron L
G
  • Locked
1973 750 Commando, transmission bug
Replies
11
Views
1,382
ashman
ashman
W
  • Locked
New Exhaust System Recommendation
Replies
2
Views
716
Fast Eddie
Fast Eddie
Back
Top