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Discussion Starter #1
When installing or removing spark plugs on aluminum heads, you might want to check the following:

-make sure the head is stone cold
-careful of cross-threading
-don't overtighten
-careful with anti-seize

If the head is warmish and worse if hot, the threads become very weak. It's very easy to cross thread ie the threads offer little resistance. It's also very easy to overstress the threads by tightening the plug too much. The threads can fail and the plug may blow out on the compression stroke. Evidence of this is alum shavings on the plug thread. Technically, that's a user fault.

If you use anti-seize, use very sparingly. Tighten the plug a little less as the anti-seize reduces friction. It's easy to overtighten the plug and have it sit lower in the combustion chamber.

So. . . heads cold, no cross thread, low tightening, careful with anti-seize.

Hope this helps

Seeker
http://pages.infinit.net/mcrides
 

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I think you should add in 'don't undertighten' as well. I'm pretty sure that's what I did wrong, in addition to not using anti-seize.
 

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Discussion Starter #4
Joel : I think you should add in 'don't undertighten' as well.  I'm pretty sure that's what I did wrong, in addition to not using anti-seize.
It's hard to undertighten, though I guess it's possible. The manual calls for 9ft/lbs torque on the spark plug. If someone is applying 20ft/lbs, they are applying way over.

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Discussion Starter #6
googolplexu : Quote (Seeker @ Aug. 17 2003, 4:37pm)-make sure the head is stone cold
Stones arent very cold in my part of the country.
That's a good point. If you're bike has been sitting out in the sun on a 100F day, your heads are not cold. Find some shade and leave it there for a while. If your heads are a little warmer you might be a little more careful.

Tip: on a cold head . . .9ft/lbs. On a hot head . . . less.

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Discussion Starter #8
ND4SPDSHO : I hope this isn't a 'speaking from experience' thread
Just another caution. We tend to think that most damage occurs when we install plugs. We put the plug in and find that it doesn't go in well and figure we cross-threaded the plug.

In fact, most thread damage occurs when sparkplugs are removed from a hot head. This is especially true if the plug has been overtorqued ie 20ft/lbs or more when installed.

When we go to re-install the plug, the damage is already there.
 
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