I went through a very worthwhile exercise the other day, to dial-in the suspension on my 640A. I can thoroughly recommend this one as an eye-opener, if nothing else. I used the process from the Orange Crush > KTM 950 Halls of Wisdom > Dirtbike Suspension Setup:
To summarise the method:
You need to set the sag first (of course) and have the correct springs. I've got the sag set as best I can with the springs likely one step out fr & rr (soft front, hard rear). Then set the compression and rebound clickers to standard.
Ride a 10-minute test loop with a variety of conditions. For me, I used the first bit of the Maungatapu: starting at the junction just the Nelson side of the ford below the caretaker's cottage, up & over the hill turning right into the dam headwaters, and return. The section includes that slippery bouldery tricky descent/climb that is always shadowed, lots of ruts with big square-edged bumps, tight corners, faster bits (not highway fast though), small jumps, rocks, potholes, loose gravel, hardpack... lotsa stuff.
Then you repeat the loop with way too much rebound (6 clicks from standard), then way too little, then way too much compression, then way too little. This gives you a feel for how the bike behaves when it is set incorrectly. Finally, you go 2 clicks at a time towards the better-handling setting until it gets worse, then come back 1 click at a time until it is as good as you can get. My bike's forks have 34 clicks of compression adjustment, and 24 of rebound, fairly typical for a dirt bike.
Results?
Not finished yet; I only had time to do basic tuning on the front, but WOW!!!The really interesting thing? Mucking up the front ruined the performance of the rear! The rear settings were the same the whole time, but handled way, WAY different depending on how the front was set. And 6 clicks was far enough from std to be horribly, horribly wrong.
Key points:
Too much rebound was instantly noticeable, and the most evil of all four wrong settings. The front packed down badly almost from the get-go (the first part of my test track was a "launch" over a contour bank followed by downhill braking to walking pace through a ford), felt like 30-50% of the suspension travel had been removed. Wheelies were much more difficult, bump-steer became apparent, it was tending to headshake, it felt like I was likely to endo over the front even on big bumps on the flat, and down the snotty section the front broke traction constantly and the rear was totally unmanageable: hopping, skipping, kicking & sliding wildly all over the place. Rear traction at all times (go, whoa, and tracking in the rough) was compromised.
Too little rebound was also bad, but better than too much. The front was pogoing a lot, felt very loose (loose = lots of fast movement), not steering as well as std since it was lifting off the ground on rebound, wheelies were easier than as std. So I backed it off 2 clicks from std as a crude adjustment which felt a bit better overall; maybe +/- 1 from there will be spot on.
Too much compression was very harsh. Wheelies were easier, but the front was skittish and the ride unpleasant.
Too little compression felt really loose, it made the rebound seem too fast/loose as well. But again, this was better than too much. I tried 2 clicks faster from std, but didn't feel it was better overall than std, so left it on std.
Finally
Can't wait to do the rear shock, as I was running it on std settings which are a long way from where I normally have it. Std is rebound 7 of 11, compression 6 of 7. Normally it's at R1-2 & C1-3 !! The latter to stop bottoming on jumps. Due to the limited adjustment positions on the shock, I would be inclined not to adjust by as much as 6 clicks, except that I normally run it 6 clicks from std so I will test it that far out.
Another interesting thing was that the std settings felt pretty good on the ride out through town and flat/fast gravel roads. On the way back, with the change merely -2 clicks of front rebound, the gravel felt marginally better, but on the streets it felt noticeably worse, quite choppy due to the faster rebound. Which just goes to show that in the adventure arena there is no one ideal setting, and furthermore, this exercise should be repeated for significantly different conditions.
Tyres were Pirelli Scorpion MX eXtra 80/100-21 @ 20psi, and Michelin Cross AC10 110/100-18 @ 25 psi.
Will report back here with rear adjustments next.
Originally Posted by Steve McQueen
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Maybe I should have run the tyres much lower but for the sacrifice of lower pressures aren't you opening up a can of worms for other things? I dunno....
Running knobbies at high pressure seems to rip the knobs off, probably because the carcass won't flex. 
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