I wonder if that will explain it?

I've just changed the fork oil on the ZZR and when I pulled the springs out
I noticed that they were the wrong way up according to the Haynes BoL. The
thin end was uppermost when it should have been downermost. I wonder if that
will explain the crap suspension that I was moaning about a few months back
[1]?

[1] Bike is fine on undulations but hit a sharp bump and it's as though the
suspension has locked solid.

 

Would have the slightest impact on unsprung weight but I'd challenge anyone
to tell the difference.

What is does indicate is that whoever was in there last didn't put it back
right.
Maybe they overfilled the oil level - that would cause the issue you recall.

 

perhaps it's a bit of a bender in the one orientation

 

No neither can I but then I'm without clue on suspension set up. It is a
variable wossname spring with the coils wound tighter at one end than the
other and it was tightly wound coils downwards whereas (according to the
BoL) they should have been upwards.

 

Putting the spring in upside down will raise the oil level (more
metal, fewer voids in the bottom of the leg), so if whoever did it
didn't set the level right, you'd have a smaller air gap which could
indeed cause the problems you mention.

 

Sounds very plausible.

 

Maybe if it's tapered it won't fit properly into some other components.

The ones on the YZ certainly had a different ID top and bottom.

 

These just sit on something with a bit of packing at the top. I think
Krusty's explanation seems most feasible.

 

Does if it's progressively wound/tempered.

 

I can see how it would affect the speed of compression over a long
stroke if there was a tight-fitting alignment insert in the bottom of
the spring (more coils touching it so more friction), but that wouldn't
cause the symptoms described. The 'locked suspension on a sharp bump'
points at either air gap or high-speed damping.

Actually thinking about it some more, having the tighter wound coils at
the bottom could also impede the oil flow through the damper rod holes.
There'll be less free space for the oil to flow into when the rod's
compressed, which could definitely affect the high-speed damping.

 

Well I've put them back in the other way up (loosely wound coils
down). A couple of hours work to put all the panels back on and we'll
see.