How to remove beyond rusty exhaust manifold bolts on 600 monster

[Nick Peace]

I have to remove the exhaust on my bike to repaint engine and swingarm and frame due to battery explosions. The bolt/nuts on the manifold are beyond rusty. The front i could probably wire brush off the nut  but the screw threads are bad for new nuts, the horizontal look like bolts, but sods law says they will probably snap. More than likely in the cylinder head. How much Heat can you apply to a head to free bolt before damage is done? I am reluctant to do this. This may be one of those impossible questions.

Any help would be appreciated
Many thanks
Nick

[bond0087]

I don't have a 600, but I do have a 2000 M750, and I've removed the exhaust when I was putting in new pistons.

On mine, all four connections to the cylinder heads were studs with nuts on them (the two on the horizontal and the two on the vertical).  Perhaps yours is different, but I wouldn't expect that.
I expected mine to be difficult, but they weren't. I sprayed a little Aero Kroil on the nuts, let them soak for a few minutes, and they came off no problem. The exhaust clamp was a whole different story, though.

Here are my generic tips for situations like this:
-Spray with a good penetrating lube and let it sit for a while, anywhere from a few minutes to a few days depending on how bad it looks and how big of a problem it would be if it didn't go well.  By a "good" penetrating lube, I mean something like Aero Kroil or PB Blaster, not WD-40. For those who don't know about Kroil, look it up, it is absolutely fantastic. Hard to find locally, but fantastic.

-Use impact force to remove it the first time around. Don't wait until you've tried twisting it for all you're worth before you start trying impact force, because you might just ruin it before you have the chance.  If you have an air impact wrench, that's great, but if not, you can hit the end of a wrench or a breaker bar with a hammer to apply an impulsive torque that will help break the fastener loose.

-Use heat, but you seem to know that. In this case, you would want to heat the nut, not the stud or the cylinder head.

Like I said, for me, the header nuts were no problem. The exhaust clamp was a nightmare.  I didn't follow my impact advice, and by the time I broke out the impact wrench, the head was stripped (it was a socket head cap screw). I tried everything on it after that, from cutting a slot and using an impact driver with a large flat head screwdriver tip to heating the clamp red hot before trying that and other things, and in the end, I had to drill out the old bolt.

Good luck!

[Punx Clever]

BLUF: Heat is fine.  You can get new studs and heli-coils to fix any thread make the beast with two backsups locally if things go south. 

When I pulled my bike apart, I had hell with the exhaust studs too.  One did twist off with enough left to grab onto with some vice grips.  However, it was corroded beyond all belief.  Penetrating lube didn't help.  I ended up having to heat the area around the stud with a plumber's torch, get a little turn out of it before it cooled.  Rinse and repeat until it came out.  But it also drug some of the threads out with it.

However, M8 heli-coils are not hard to come by and it was an easy repair once the stud was out.  Also, my local Ace hardware had M8 studs to replace the old ones with.  Might as well do all four at the same time.

When you put everything back together, a bit of Anti-seize is a good idea on the exhaust studs.

[Slide Panda]

Penetrating oil and patience. Something like PB Blaster or Sea Foam deep creep applied several times, well in advance of and immediately before you get to work. Say you're planning to do the work this coming weekend - give the nuts a spray each work day evening when you get home. Then when time comes to get to work, give them a spray about 15 min before you put tools to them.

The exhaust nuts are a copper alloy - not iron/steel so they shouldn't be rusted. The studs might have surface rust and be grimy as well, but you should stand a good chance of getting things free with some cleaning, oil and patience.