Exhaust pipe nuts...

[headtube]

Continuing to discover many new things about the 79 Airhead. Just how far do exhaust pipe nuts thread onto the exhaust port. Are there different sizes of nut for different models? Both mine turn a couple of threads then stop dead. It seems to me that these should thread on close to the threads end. Are they tapered? I'm not using a special tool. Perhaps there may be an issue. Thanks.

The photo shows the nut at its limit. They are super tight at this point.

[ritetwist]

You are going to need some threads cleaned.Probably both the male and female ends.
Could be a lot of hardened carbon build-up in there.Threads on head (male) should just about disappear.
They are not a tappered thread.There is also a thread cleaning tool (metal),with lots of different pitches and thread sizes.You will need a metric one, I believe.That will work for the male end only.
Good luck.

[bmwrench]

Don't attemp to keep turning them. They have seized to the heads and if you force them off you will take the cylinder head threads with them . You'll have to cut them off. There are many methods for doing this, but I keep returning to my jab saw-a handle that holds a hacksw blade. Cut between the fins on the nut until you can see threads, then split the nuts with a chisel. Then spread the nut with a Channel Lock plier and slide it off. Get a thread file and clean the threads until a new/good used nut will thread on without force, after first coating with anti-seize.

[Stan_R80/7]

The head has external threads. The nut has internal threads. Count the threads in the nut and compare the internal nut thread count to the external threads count - its basic math. If the two do not match, there is a problem and the threads probably need cleaning.

[headtube]

Originally Posted by bmwrench

Don't attemp to keep turning them. They have seized to the heads and if you force them off you will take the cylinder head threads with them

They are not seized. Both sides turn on and off but stop at a couple of threads.

[Wirespokes]

Then clean the threads until they thread on easily!

I've even heard of polishing the exh stub threads with polishing compound. Not sure that's necessary, but do clean them all up, at least with a wire brush and dental picks. A right angle pick may be needed for the exh nut threads.

[bmwrench]

Originally Posted by headtube

They are not seized. Both sides turn on and off but stop at a couple of threads.

Yes, that's exactly how they behave, and if you persist in trying to thread them off you'll find out what happens. This has been going on with these nuts since 1977.

[boxerboy81]

Originally Posted by Wirespokes

Then clean the threads until they thread on easily!

I've even heard of polishing the exh stub threads with polishing compound. Not sure that's necessary, but do clean them all up, at least with a wire brush and dental picks. A right angle pick may be needed for the exh nut threads.

Once the threads are clean, the star nuts should spin on all the way, nice and easy. Any obstruction represents a possible point of damage.
When you're happy that the threads are good, use some anti-seize on them to prevent future issues.

If they get stuck, it's probably safer and ultimately cheaper to cut them off and replace with new. This is what can happen...

...and here is another thread about repair and alternatives...http://www.advrider.com/forums/showthread.php?t=236601

[nhmaf]

+1 with the above - if the nuts get tight trying to turn them off, and shooting some PB Blaster or similar penetrating lubricant in there doesn't change things (if there is some carbon buildup that generally does it) then DO NOT try to turn them any more and just cut them off! A new set of nuts will cost you less than $10 apiece. Sending your heads out to have the exhaust ports milled, welded and recut with threads will cost you around $200 apiece.

[DaveBall]

Hey guys, I don't know what a bunch of you are missing. Headtube has clearly stated that the nuts come off just fine. His problem is putting them back on. Quit with the advice to cut them off. He has them off.

Beadtube, all you need to do right now is to clean those threads on the head stub and clean out the threads in the nut. Brass brush that looks like a toothbrush works very well on the nuts. Can be done on the head stubs as well, but I used a brass brush wheel on my dremel. WEAR SAFETY GLASSES!

Once you have them nice and clean, try the nuts on them with maybe a little light oil. Once you are happy with them spinning all the way on and off, you can reassemble but remember to use some Anti-Seize, which will help you remove them the next time.

[bmweuro]

Read this before you go any further. http://boxermetal.com/exhaust-nut-maintenance/

[Bill Harris]

Look closely at the threads on the head stub-- if they look snarfly, they'll clean up nicely using a triangular file, but use a light touch. If the internal threads of the exhaust nuts are rough-looking, they can be cleaned up, but weigh your time & trouble against the $35 cost of a new exhaust nut.

[ozmoses]

As the OP is wondering, are they all the same size?


Is it possible these have been previously repaired/re-threaded?

[ME 109]

Different for /5 + /6 in the way of bigger fins on the nuts, but the thread may be the same.
All /7 appear to be the same, 77 onwards, including monos.

[disston]

All the Airheads have the same thread size. Earlier bikes have the nuts with bigger fins. The nuts are interchangeable.

Does the exhaust leak at the junction?