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Discussion Starter · #1 · (Edited)
All right, I was at the track for three days, and my suspension guy was there, so I took the opportunity to have him take a second swipe at this front end. For reference, we lowered this bike, stiffened both front and rear, but more or less left the valving stock. It was a big step forward, but there was still harshness in the front, causing the bike to understeer (push) on any bumps or with mid corner steering corrections. It also fely pretty much locked up at full lean. I could ride pretty hard, but it was nerve racking as I approached race pace.

So I pulled the forks monday night and Peter pulled out the compression stack. We chatted a while, and Peter ended up eliminating most/all of the low speed compression damping. We needed to get the suspension to drop a lot sooner/easier. We were confident that my spring rates, while stiff, are appropriate for what I'm doing with this bike, but the supension just wouldn't start moving.

Put the forks back in and I could feel the difference just putting around the paddock. Out on track it was a different bike. Loads of feel and feedback, much quicker turn in and fast direction changes. It handles the flat, bumpy part of Loudon's T3 without any drama, and I could finally lean it over all the way through those bumps. Mid corner corrections are finally possible/easy. In a nutshell, the bike finally works as I had envisioned it. Firm and controlled enough to run race pace on track, but plush enough to make a great streetbike as well.

Some video evidence to follow!
 

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Discussion Starter · #3 ·
Here's a few laps at the end of three days. It was 100 degrees out and the bike was suffering for horsepower. Nice precise lines finally. There is a remote camera on the ground in T11, and I'm making it wobble with each pass. (that stuff ain't cheap, so I must have been confident!)

http://youtu.be/WmvAn_RnORY
 

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i have never been happy with the way my 690 smc felt untill recently, i took some advice u posted before and stiffened the rear and softened the front. Also dropped the front 15mm and the difference is unreal! I plan to take the spacers out the forks soon too, have u had the shock revalved also or jst the forks? Also have you ever noticed the play in the forks? Ive checked 4 690 smcs and they all have quite a lot of play in the forks, I fitted new bushes and they are a bit better but its still strange i think?
 

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Discussion Starter · #5 ·
I find the shock to work very well with the stiffer spring and stock valving. I do not have any play in my forks. I have the spacers out and springs cut so that they just rattle a bit when the fork is unladen (0 preload when off the bike).

Reducing the low speed compression damping made as big a difference as the other changes. It's a huge leap forward.

BTW, the stock valves themselves are good. Plenty of flow. No need for any upgrade. Stiction is still an issue, but now that I have made this last change, I don't think stiction is really playing much of a role, if any, in the front end issues.

Some fellow racers rode this thing, and described the front end as "magic". Incredible lean and corner speed with none of the chatter that plagues nearly every motard under those conditions. In the vid you can see the incredible drive I was getting out of the turns. Weeee!
 

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Yes i assume you have less play because you have shorter forks? If i take all the spacers out the top of my forks do i have to put something (small spacer etc) to stop it damaging where it locates under the top cap?
 

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I wont bother then! Thanks for your advice! Great video by the way and glad your happy with the bike, its a good feeling...
 

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Discussion Starter · #9 ·
I think you may be referring to stiction when you say play? If you bounce the forks, they rise and drop, but stick a little short of settling back down all the way. That might feel like "play", but it's not. If you sit on the bike it settles all the way. no play.

They all have quite a lot of stiction. whether it presents any actual handling problems is debatable. Perhaps the forks would feel a tad smoother without it. but under load, it's much less of an issue than sitting in the garage.
 

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Paab,

That is fantastic news, thank you for helping to evolve this great motorcycle!

Cheers,
Roy
 

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no its not the stiction I talk of! If you have the front wheel in the air as if checking steering head bearings, grab the fork at the bottom by the axle pinch bolts and rock the forks forward and back, Play can be felt (and seen before I had the bushes replaced) between the stanchion and the slider...

All in all its not too bad at the mo since having bushes changed and im sure it will decrease when sat on the bike, and even further more if you have shorter forks?
 

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Great!!! That vid is crazy!

All my bikes are outdated suspension wise, but I've found for the track/street your concept does work best. The only thing that changes for me is turning rebound up on the track and more down on the street since I live in Cincinasty (speedbump, aligator cracking; strip seal city).

Thanks for sharing
 

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I've totally rebuilt my forks myself so no fear of diving in to them. But the actual shim stack and number of them is too much science for me to just take out some of the stack valving.

Do you have more detail as in what stack shims were used in place of the stock ones or which valving washers were removed and not replaced by thinner ones?

Any documentation at all from your suspension guy?


Thanks
 

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Discussion Starter · #14 ·
Peter Kates of GMD computrack has all my data and can reproduce my forks for anyone. I can't share what he has done, as that's what he makes a living doing.

I can't wait to take a street ride and see how they do out there. I'm certain they will be fantastic by compariso with stock, or even where I was before this little adjustment.
 

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Discussion Starter · #15 ·
Also Intune, I have no idea! We talk, he listens, or doesn't, and makes changes. I ride. That's how we work.
 

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gotcha, no worries, I totally respect 'respecting' someone else's work and way of living. I just thought maybe you worked together on it and knew what you did to the valving.

I'm in the poor house right now, so no custom valving for me unless its in my garage in my own hands.

BTW FWIW ~ I thought running no washer at all (pre-load spacer) was bad for the internals and would cause the steal spring to eat into the softer aluminum of the cap. At a minimum causing lots of unwanted debris in the fork. I am running the smallest nylon washer about 2mm on both sides so the spring doesn't bind or eat into the cap over time.

~ and also, not that I'm saying the direction isn't the right way to go, but from the eyes of a complete suspension tuning novice I would think high speed compression is waht would help with compliance and feel over the rough stuff. Low speed compression I thought is what counter acts the fork dive under braking. Guess I need to re-read the Suspension Bible again. I thought though high speed compression = damping for high rate of internal componenet compression speed through the fluid vs. low speed compression = damping for lower speed fork compression internals though the fluid, (as in the of rate of speed of the moving fork internals compressing into the spring).
 

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Discussion Starter · #17 ·
Reality is a little more complex than that, though. My problem was not with big hits, but more a feeling of hydraulic lock at lean. If the fork can't start moving, it has no prayer of absorbing ripple type bumps leaned over. The tire will flex a bit. then slide. Push. The bumps on a race track can barely be seen with the eye. So in this case, low speed compression damping was the culprit. I'm now able to add back in the compression clicks that i removed to try to cope with this, giving me more plushness AND more big big bump compliance at the same time.

Distinguishing between what engages low speed damping vs. high is not that obvious in most cases. Its a bit of trial and error, even fro the pros.
 

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Discussion Starter · #18 ·
Took it out on the street to get it inspected today. It's transformed there as well. Even with my stiff springs, the bike is not shaking my fillings out over manhole covers, expansion joints, cracks etc. I feel much less of that stuff. Off camber, bumpy turns are no longer a white knuckle affair.

The bike is also MUCH lighter steering. I was always shocked by the heavy feeling front end on this bike, but that sensation is gone.

I know Peter took this bike in the opposite direction to most tuners, but with this one change, the whole set up just works amazingly well. I wish I hadn't waited so long to let him go back in the forks. I'm one happy camper.
 

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VERYY interesting!!

Peter Kates of GMD computrack has all my data and can reproduce my forks for anyone. I can't share what he has done, as that's what he makes a living doing.
I can't wait to take a street ride and see how they do out there. I'm certain they will be fantastic by compariso with stock, or even where I was before this little adjustment.
I live in Moscow, Russia and I was a bit difficult to send the details to set up :headscrat ,so if someone will share the information necessary to setup - I'd be very grateful.
You will not believe it, but I alone in all the capital it needed.
others simply alter the bike, cursing KTM.
Thanks to you, and especially Intune, I have the best KTM among all my friends :)
 

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Now a odd question. Can you still corner foot out after this set up? Im going to start changing my settings when I get home. But Im still a foot out guy in the long run.
 
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