Hi

I want to remove two rusty, seized 6mm exhaust studs from a 45 year old Honda 4 stroke alloy barrel, as I need to install longer ones.  I have soaked them in WD40 for 2 weeks.  I have also heated the studs to cherry red.  I then  tried turning them, using two locked nuts, but they won't turn.  I am afraid they will shear off if I put any more pressure on them.  They are not currently snapped off, so I don't need to drill them out.  However, I do want them out.

What to do?  Anyone have experience of doing this?

Thanks

They were hard to get out 40 years ago, have you tried heating the head rather than the studs ? 

If you end up cutting them off, at least you have a flat face to drill.

 b40rt is correct, You need to expand the surrounding metal, not the studs, so that's where the heat is required. Go easy with the heat, as heating alloy anywhere near

"cherry red "  will result in rapid meltdown.

Might be worth trying a small Stillson type pipe wrench near the bottom of the stud where it goes into the alloy. This will minimise the risk of the stud twisting/ snapping further up.  

Oven with most heat you can adjust is a good way as aluminium is expanding three times as much as steel already 250 deg might leaving the item inside for at least half an hour to one hour will do the job.

Aluminium also transfers the heat so well this makes it so difficult to heat up just areas, if you heat up everything it works much better and will also not lead to any wraping!

Edited November 28, 20196 yr by pschrauber

Hi there I don't really rate wd40 for a job such as that. I would only use plus gas spray best stuff I've used . A good soak in that and as has been said .good pre heat on the  aluminium away from stud area .you won't hurt it as melt point is 700 deg c  for most automotive aluminum  . Hope this helps

50/50 mix of ATF and cellulose thinners works well

As above, heating the head is the way to go. From experience you'll be heading for around 400 C, At work I use the oxy acytlene torch for this, but at home I use an LPG burner, (its a little safer as far as melting the work goes).

The thread in the head may get damaged as the studs come out, so I'd suggest helli-coiling  or using thread inserts after extraction in the head. Then you can use, bolts, capscrews or studs, and they will be more serviceable. 

Oh be careful not to overdo it and have valve seats etc come out, Good luck

A penetrating oil that follows heat helps.

I used Kroil.

Several heating/cooling cycles helps, so does tapping sharply and repeatedly with a hammer to help loosen the interface and help the oil penetrate.

Dissimilar metals make a small electrical charge that promotes oxidation and they virtually weld themselves together.

I would say that 10-15 heating/cooling cycles would not be unheard of. 

That's a hostile environment.

Put the new one in with high temp anti-seize.

On 11/28/2019 at 6:20 AM, stpauls said:

Hi

I want to remove two rusty, seized 6mm exhaust studs from a 45 year old Honda 4 stroke alloy barrel, as I need to install longer ones.  I have soaked them in WD40 for 2 weeks.  I have also heated the studs to cherry red.  I then  tried turning them, using two locked nuts, but they won't turn.  I am afraid they will shear off if I put any more pressure on them.  They are not currently snapped off, so I don't need to drill them out.  However, I do want them out.

What to do?  Anyone have experience of doing this?

Thanks

If you do break the stud don't panic ! place a washer over the stud get some one to TIG weld the washer to the stud then weld a nut to the washer. It worked on a Honda Fireblade did it institue.