Hi, I see that no one responded to your question in 6 days, and we don't want to leave anyone hanging, so I'll give you my two cents' worth.  I use Speed King pedals exclusively, one for each of my 4 vintage Ludwig kits and a spare in the trunk of my car.  

Of those 5 pedals, 3 of them were "tuned up" by Vincent Leef of Vitalizer Drums.  But I don't think he is in business anymore.  That's too bad, but the gist of his work was to replace the two bolts that fasten the heel plate to the floor plate.  Nylon washers removed the squeeks there.  And he replaced the bolt on the forward pivot (sorry but I don't know the correct terminology).  What I call the pivot is the hinge that is forward-most on the Speed King assembly.  Vincent's work also removed that squeek.

I've noticed on one of my Speed Kings, that the forward pivot can scrape against the batter head of the bass drum.  But a slight adjustment to the clamp on the pedal onto the hoop of the drum will solve that.  

I don't know what you mean by "that clanky sound."  What I call "the rocker" (the curved piece that rocks between the upright posts when you work the pedal, and it holds the beater) does have some play in it, at both upright posts, but it's nothing you can normally hear (unless you place a mic adjacent to the pedal, I suppose)..

I assume you've taken the chrome-plated end caps off the posts and cleaned - and then lubed - the bearings.  The springs in each of the posts should have some lube on them, as they scrape along the inside of the posts, but I've never detected any noise coming from the motion of the springs within the posts.

That's all there is to a Speed King.  Delightfully simple!  And lightweight.

One last source of a squeek.  The flat piece of steel that engages the toe of the pedal with a J-shaped end can cause a squeek that can be silenced with a little grease or silicone.  Vincent put a nylon "roller" in the toe of the pedal, which engages the J-end.  That eliminates a squeek.  

How tight or loose to adjust the springs?  That's personal preference. How stiff do you want the springs?  What tension gives you the best feel, the best rebound?  I take care to screw down the two springs at equal tension (as best I can; the same amount of turns on the screw), for whatever that's worth.

What I would recommend you do is get down on your hands and knees and work the pedal slowly to find the source of the "clanky sound."  Or if your knees are shot, put the pedal on your work bench or the kitchen table(!) and slowly work the pedal until you can determine what part is noisy.  If you have an old, perhaps abused pedal, something might be bent or otherwise damaged. Good luck with it!

Regards, Marty Black