Exhaust header nuts/bolts/ threaded bar

[Ron1000]

Guy's,
Had a wee bit mechanical difficulty today, I've been riding some particularly bumpy roads lately and i have noticed that my front header is rattling around to the point that it has started blowing.

I have checked it and managed to turn the thread bar part until it was as tight as i dare go. However it was still rattling, I can't adjust the nut part as it's rusted solid. On the plus side I've managed to get the whole threaded bar & nut assembly out and ready for new ones…easy you might think however I'm wondering.

How come it was rattling when fully tight? Is there a perished gasket in there?
And I've got some rather nice titanium bolts that just so happen to fit, however to take the slack up and get it nice and tight i do have to take up a lot of thread (longer than the standard threaded bar). I'm wondering if that's ok or if the thread would protrude into the engine some how and even if it's a good idea to use a standard bolt instead of the correct threaded bar & nut assembly

Thanks guy's

[Dookbob]

Hi, Due to the fact that one day you, or someone else maybe,will have to remove whatever you choose to fit, I would replace the seized nuts and studs with the standard original type of studs and nuts. I would also give the threaded parts a dose of copper slip before screwing everything back together, and you will need a new compression gasket.

[Mr Gazza]

A stud and nut will be better than a bolt, as it will not wear the thread in the head. A broken stud is not too bad, but a torn thread in the head is not so good.

I couldn't comment with any authority or experience about using Titanium in Aluminium, but I reckon a Ti stud with plenty of Coppaslip would be okay.

I have stainless dome nuts on the standard steel studs on mine... well greased up with copper.

Sounds like your gasket ring has gone, and possibly the collets have rusted, eroded or collapsed?

[BigOz]

Galvanic corrosion between Aluminium and Titanium is an issue as is galling, both issues are greatly mitigated through the correct use of good quality assembly lubricants or thread-lock where appropriate.
A Copper based anti-seize will work but I would favour a ceramic based product in any high heat application.
For exhaust applications where future serviceability after many heating/cooling cycles is a factor, it is hard to beat a stud and copper nut combination.
While the use of a bolt is not uncommon, trying to use a bolt that could be overlength is a recipe for an expensive headache.

[Luddite]

Hi, Ron.

There is a gasket - part no. 037084005, always handy to have a couple spare. To replace the stud and nut you'll need 76640172A and 74840331A respectively. Give Craig and Luke a ring at Moto Rapido 01962 873981 and you'll have them in a couple of days (don't forget your UKMOC 10% discount).

There are a couple of possible reasons why you couldn't tighten down the clamp. If you look at the stud that you removed you'll see it is threaded at each end with a blind, unthreaded section in the middle. If the stud had backed out from the head and then seized in place, the shoulder of the unthreaded section might have been above the exhaust flange preventing the nut from bearing down on the flange.

Alternatively, if the nut became loose, perhaps corrosion built up above the unthreaded section preventing the nut from travelling far enough down the stud to tighten the collar.

And +1 for the Coppaslip.

[Ron1000]

Cool guy's I'll leave the Ti on the shelf and get the bits ordered, bit of a pain getting that front pipe section off, I believe the exhaust, mid section, springs and front o2 sensor will all have to come off to get to it properly.

[utopia]

A stud and a length of threaded bar are two fairly different animals.
Not only is there the unthreaded central area, which limits how far the stud can be screwed into its housing (in this case, the head) but it is not uncommon for this thread to be a slightly tighter fit than the other one. I don't know if Ducati head studs are like this, but the point is, it ain't just a piece of threaded bar. The threads will quite possibly both be cut more accurately too, and the steel may be of a higher grade.
I would use std studs .. or titanium studs made specifically for the purpose if you must, but not any random bolt or threaded bar.

Now, that central unthreaded section (further to Luddite's comments) ....
So if the stud was screwed in fully when it was fitted, until the unthreaded bit prevented it from going any further ..
And then the whole thing was clamped up and the nut subsequently seized in that position.
And then the compressible exhaust gasket yielded during use until the exhaust was free to rattle.
The seized stud/nut assembly cannot be tightened further, to re-compress the gasket, because the unthreaded bit is already hard against the head.

That's how come it was rattling around when it appeared to be fully tight.
And yes, you could say the gasket was "perished" .. but they're compressible and will lose their spring in use somewhat, so "squashed" might be a better term.

When fitting the new studs, you will need the correct grade of Loctite for them.
For my old 2-valve motor its Loctite 243, but you need to verify that its the same spec for your engine.
The usual way to drive the studs in is to fit a pair of plain nuts to the outer end and tighten them against each other. Then use the hex of the outer nut to spanner the stud in (presumably until it bottoms on the plain central bit).
The threads in the head need to be clean so the Loctite works properly .. but I would be wary of putting a tap down them for fear of cutting the thread slightly oversize/loose .. which is the last thing you want.
A clean, loose fitting bolt sprayed with solvent cleaner and wound gently in and out .. and repeat .. should do the trick. Don't force it though .. those threads are precious.
And make sure that the studs go in the right way round .. if there is a difference.

You could use stainless dome nuts instead of the std ones BUT they are tricky to use because of the danger of the stud bottoming out in the dome before the nut is fully tight.
If you feel competent to deal with this then go ahead (I have) but if you're not sure, then I'd use std nuts or copper ones in the same style.
And copperslip is essential .. but again, with the dome nuts you need to be careful to use it sparingly enough to leave an air gap in the dome (or drill a bleed hole) so you don't get a(n) hydraulic lock before the nut is fully tight.
Std nuts (and studs) is probably the way to go.

And don't replace any "while you're at it" that you don't have to .. you could easily open up a whole basket of snakes.

[Luddite]

When fitting the new studs, you will need the correct grade of Loctite for them. For my old 2-valve motor its Loctite 243, but you need to verify that its the same spec for your engine.

Utopia is right in all he says, including the grade of Loctite - according to the Evo workshop manual, it's still Loctite 243.

[utopia]

..... on this occasion. :rolleyes:
;)

[slob]

Take a look on ebay you can buy copper plated nuts (typically for BMW exhausts) these withstand the hight temperatures well without seizing and are more robust than the stock ones.

eg http://m.ebay.co.uk/itm/25x-M8-Copper-Flashed-Exhaust-Manifold-8mm-Nut-High-Temperature-Nuts-/361488910213?hash=item542a6b0785%3Ag%3A7a4AAOSwHpt Y%7EeUx&_trkparms=pageci%253Ac1074883-444d-11e7-8aa4-74dbd18006e0%257Cparentrq%253A53729fc015c0a9e4b500 0540fffdf698%257Ciid%253A7

[Ron1000]

Cheers guys, luckily I've got the correct loctite and I'll phone moto rapido tomorrow when they come back from bank holiday.

[slob]

...sorry, not a great example I linked to, look for a flanged nut and double check the thread pitch.

[Ron1000]

Well the first bit was easy, exhaust disassembled and ready for new gasket and studs / nuts.

Found the problem…there is not gasket, I'm assuming is been completely destroyed and been fired out the back as particles. Lololol.

Threads all checked and look in nice condition so not much to do but wait for new bits now.

I'm alsmost disappointed, i was looking forward to hours of shed time. Got a nice pic of the exhaust valve tho.

[Dukedesmo]

Found the problem…there is not gasket, I'm assuming is been completely destroyed and been fired out the back as particles. Lololol.



Quite possible, mine had a stud back out/disappear and the resulting loose fit disintegrated the gasket, the same happened to my Guzzi, which actually uses the same gaskets. I found the silver metal over 'asbestos' (substitute) gaskets are better than the round section copper gaskets that some sell.

I now have a system held in with springs and no gaskets but it still uses the studs/nuts to hold on the spring mounting flange.

[utopia]

But .. do make absolutely sure that there is no gasket in there.
They can get squashed so solidly into the exhaust port that they are sometimes hard to see (if they're the silver coloured ones).
You're looking for a circular line, a couple of mm in from the apparent sealing face (if there is a gasket).
You're probably right and there isn't one there, but its definitely worth looking closely to check.

[Ron1000]

Hey guys,
Parts finally arrived and fitted…no been on the bike for 12 days, no biggie weathers been poor up here anyway.

So exhaust studs, gasket and copper nuts fitted. Pretty easy in the end, has anybody got a torque setting for how tight they should be? I've went 20nm it seemed like a reasonable figure and at least I've got an actual figure to work with instead of just going too tight.

[Luddite]

Have a look here, Ron, which lists all the torque settings for the Evo:

http://www.ukmonster.co.uk/monster/showthread.php?p=531319

You need to nip them up first (6Nm) then tighten them to 24Nm.

[Ron1000]

Have a look here, Ron, which lists all the torque settings for the Evo:

http://www.ukmonster.co.uk/monster/showthread.php?p=531319

You need to nip them up first (6Nm) then tighten them to 24Nm.

Cool, i nipped up the studs then fitted bolts and tightened to 20nm. I'll check they are still tight now I've given the bike a run…I'll add that extra 4nm too.