Hi Basspete, I had the same stud problem with my bike when I got it. After I extracted them, I replace them with st/steel studding cut to the right length, and fitted them with thead lock. I could go ino a load of scientific bollocks, but the studs won't corrode as much in the alloy head, and the mild steel fixing bolts will corrode before the stud leaving the stud intact. Worked great on mine, and really easy to get off.

I think I just finally found the last bit of the jigsaw.....the mechanic who put the head on, had just bolted the head I'd got straight on after a quick look over.....I was cleaning up the valves today,when I noticed fresh air between the inlet valves and the head. Yep, both inlet valves are bent. Another mate who is a mechanic (and also rides bikes!) is going to take both the old head and the new head into his work, and swap the (straight) valves from my old head into the other head. (with the much better cam and journals) I woulda had a shot myself, but he offered and has all the tools at hand to do it.

I'm seriously thinking that me and my XT may be reunited on (and off!) the road just in time for the first anniversary of the twat in the AA lorry dropping my bike off the back, and starting the whole sorry episode off.

God, I canny wait to get on the bloody thing again! its done my head in, but..... hey......you all understand!


Cheers

Pete

Oooooh.

Stainless and alloy are a really bad mix, much worse than steel and alloy. The issue is not corrosion caused by external elements per se, but corrosion caused by galvanic action. You know that "gunpowder" smell you get when you crack a steel bolt in an alloy block? Galvanic corrosion caused that.

And now the really fun news. Galvanic corrosion affects the least "noble" metal, which, in short terms, means that it's the threads inside your head that will corrode before the stainless. Galvanic action between alloy and stainless is significantly higher than that between carbon steel and alloy, so although your studs might last longer, your head probably won't.

My 550 is 25 years old now, and yes, I need to replace the studs (and a fair amount of other boltery) - I'll be going steel all the way.

As an extra bonus, consider that if you have a system that's liable to be subject to galvanic action, the standard way of avoiding this without using a barrier membrane (not possible in most applications) is to use a "sacrificial anode" made of a metal that corrodes first, thus saving your expensively machined bits; the most common metal used for this purpose is magnesium. A good reason not to use stainless sidecover bolts, considering the makeup of XT sidecovers...

hi Tufty

For significant galvanic corrosion to take place, some electrolite needs to be present (i.e. water). With the studs loctited in, the two metals are in an anaerobic environment, and corrosion reduces to an insignificant level.

But hell,whatever floats your boat. I took my exhaust off this weekend after nearly two years with a 10mm open end spanner.
LOL
dave.O

Hey Dave.

Maybe I'm too paranoid, then :)

Simon