Exhaust nut removal

[Duccout]

Yes, as I described in my earlier post, grinding these out is a real PITA! As Bill and George have said, the exhaust pipe is in the way of the nut, so I had to first grind strips out of that, to enable me to get to the brass nut, and then grind slots in that, then chisel the lumps out; what a job! And then to add insult to injury, my thread was completely corroded away, leaving just a white powder, no wonder the nut would not unscrew.

[Dodge]

Hurrah!! The nut is off and the threads look OK. I used an angle grinder to remove the top of the nut and the exhaust header pipe. Then a Dremel with a small cutting disk until the whole thing was cut to pieces from the inside without touching the thread. The thread in the head looks good but is well clogged with ‘Firegum’. Some idiot (me) used copious amounts of it and this is probably why the nut didn’t release. I have been carefully removing the hardened putty with a fine copper brush on the Dremel but it is very slow progress. Is there any product that will soften the putty which is now rock hard and probably stronger than the alloy head?

[Duccout]

Well done! What a job. I can think of a couple of things to try to soften the fire gum, one is paint stripper and the other cellulose thinners, although you would have to keep reapplying the thinners, or may be rest the exhaust port in a pot of it, outside too, as the fumes are horrendous.

[themoudie]

Aye Dodge,

Here is the link to the Holts Firegum safety data sheet: Holts Firegum safety data sheet

When you read this you will note that the main ingredient is Sodium Silicate solution that would indicate that it is a water based paste/solution. Once the water evaporates it forms a glass like solid and is also used to petrify wood and seal eggs for preservation. There are chemicals that can soften this 'glass' but unless you know an industrial user who is prepared to decant a small volume from a 25l or 250l container and are prepared to wear the necessary protective clothing I wouldn't bother.

Personaly, I would be very wary of creating a lot of Sodium Silicate dust and then breathing it! Pneumoconiosis (fibrosis of the lungs) is a potential problem from inhaling the dust created by the Dremel fine copper brush technique you are using to remove the Firegum from the threads. I have used a fine pointed pick either dental or engineering to gradually remove the Firegum from exhaust port threads on Ducati single exhaust threads.

[N.B. Gianni's comments in the folllowing post of this thread regarding the effects of acids on Sodium silicate. BR_26/02/2021] A mild acid might help ease the Firegum's grip, as it is alkaline when wet/in solution, but beware of excessive fizzing/efervescents and the fumes that might be produced. You might be surprised at what lemon juice might do (I HAVE NOT TRIED THIS MYSELF!).

If you use lemon juice, make sure that you give the head a good wash with hot water and detergent followed by a thorough rinse in cold water.

Good health, Bill

[Gianni]

That firegum sounds like some preparation for patching mufflers with holes in them. Sodium silicate, commonly known as water glass is manufactured by dissolving silica (sand) in caustic soda (NaOH). SiO2 +2 NaOH-> Na2Si03 + H2O. If you add acid to sodium silicate, you will drive the reaction in the reverse direction and turn that goop in your threads into a much harder sand matrix. I used to buy sodium silicate in 640# net weight drums.

I think a good water soak would be worth trying, to see if it would soften enough to chase the threads with a pick or small welders brush.

[Dodge]

A pleasant afternoon in the Cornish Sun (with face mask on) and Dremel in hand, grinding the offending ‘Firegum’ paste off. I found that continuous drenching in WD40 (is it alkaline?) appeared to soften the glass hard gum. Frequent vacuum suction - reminiscent of a visit to the dentist and the offending grunge was finally whittled away. An NOS exhaust nut now easily screws in leaving a 4mm gap (external) between the nut collar and the head. My guess is that the exhaust nut has reached the end of the thread. I think I have finished the job – Hurrah!!

One last question and the reason I resorted to ‘Firegum’ was that the offending nut always worked loose – even when wired closed. Now, my amateur attempts at lock-wiring are probably to blame; but, how should the exhaust nut be wired to stop it moving?

[Jordan]

A spring instead of wire?

[themoudie]

Aye Roger,

Some will tell you that if you tighten the exhaust collar sufficiently, it shouldn't require lockwiring!

My experience is to use the proper heatproof, flat both sides, alloy encased heat resistant fibre 'O' ring, Ducati Equ. 0400.84.030. Crushable copper 'O' rings may seem like a good idea, but as they crush, so the exhaust collar slackens.

My exhaust collar has 4 x 3mm holes drilled every 90° between the fins and as you can see from the attached image, I use a double swivel ended spring between the frame and the twisted stainless steel lockwire. You could lockwire directly to the frame or drill a hole at the base of a rocker cover fin. However, this always requires the wire to be cut if you need to remove the collar or the rocker cover. The spring removes this need to cut the wire.

Having liberally applied copper grease to the collar threads, tighten the collar with either a 'C' spanner of the correct radius or a multi face spanner that grips the sides of at least four of the collar's fins, as tightly as possible.

Gland nut pliers are really a bad idea as all the torque is applied through the top of a single fin and usually results in at least one broken fin!

My apologies if this reads as an instruction to my Grandmother how to suck eggs!

Good health, Bill

[blethermaskite]

so in my experience the trick is to tighten the exhaust nut when the engine is at full operating temperature, which is when normally the alloy in the head is most expanded, you really do need to buy or make a proper muli catch spanner that is a good fit on the nut fins so you can put a bit of effort into getting the nut tight......no matter how much you try to tighten that nut up with a cold engine it will loosen again.
I just use green plastic covered garden wire ( its about 1.5mm) with the plastic stripped of and lock it to a hole in one of the vertical fins above the exhaust port after a few hundred miles it will need a wee nip up tighter and then will be fine and not loosen
Cheers,
George

[Ventodue]

<snip> in my experience the trick is to tighten the exhaust nut when the engine is at full operating temperature ...

Same, George .