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Question YSS Front Suspension

Properties

Density at 15 ºC 0.893 kg/l
Viscosity 20 ºC 269.8 mm²/s
Viscosity 40 ºC 99.4 mm²/s
Viscosity 100 ºC 14.8 mm²/s
Viscosity Index 155
Flash Point COC 234 ºc
Pour Point 33 ºc

mm2/s = cSt

99.4 cSt at 40C strikes me as a VERY viscous (thick) fork oil.
 
Yes, what I’m saying is that drilling (enlarging) or not drilling the damper tube holes out will have such a large impact on the outcome that it hardly seems like an option to be decided simply on convenience. It like saying if you don’t feel comfortable cooking your steak, no need to, you can just eat it raw. Likewise you can save the trouble of drilling holes, and just have a stiff suspension.
Thanks 670. That is the information I was looking for and what I was leaning toward. I appreciate you taking a lot of time to respond and trying to understand what it is I am trying to accomplish. I'll drill it out and see where it goes. It's a few weeks out until they get here so I'll order replacement rods and a couple of different fork fluids based on some of the contributions here. Like I said, I like to tinker so it's not a big deal taking forks on and off.
 
I installed the YSS springs and emulator, went with a 5wt (15.9 cSt- 150 VI) oil, did not drill the damping rod, 1"click" down on the emulator, and a bit too much preload. I have not set up the sag yet. Night and day improvement. The combination of the front and rear suspension upgrades made this bike super smooth and so much more enjoyable to ride, IMO. The nosedive on braking is different...less dive and a slower rate. The ride and handling are both transformed for the positive. The sense of speed is entirely different too. For instance, it felt like I was going 60 but was travelling at 75. I'm not sure if that makes sense the way it is written but it's the best I can come up with. I intentionally aimed at potholes that I avoided before. The suspension upgrades really absorb the energy. Though I never was concerned about the handlebar vibration, it too is greatly reduced. Took about an hour and half after removing the front fender until it was ready to ride. That is including a challenge getting the axle to line up in the threads (I was working alone). I bled the brake lines while I was at it.
 
I installed the YSS springs and emulator, went with a 5wt (15.9 cSt- 150 VI) oil, did not drill the damping rod, 1"click" down on the emulator, and a bit too much preload. I have not set up the sag yet. Night and day improvement. The combination of the front and rear suspension upgrades made this bike super smooth and so much more enjoyable to ride, IMO. The nosedive on braking is different...less dive and a slower rate. The ride and handling are both transformed for the positive. The sense of speed is entirely different too. For instance, it felt like I was going 60 but was travelling at 75. I'm not sure if that makes sense the way it is written but it's the best I can come up with. I intentionally aimed at potholes that I avoided before. The suspension upgrades really absorb the energy. Though I never was concerned about the handlebar vibration, it too is greatly reduced. Took about an hour and half after removing the front fender until it was ready to ride. That is including a challenge getting the axle to line up in the threads (I was working alone). I bled the brake lines while I was at it.
Sorry...I meant to say thank you to all of those who helped me figure this all out! That was actually the primary reason I wanted to post...got distracted by how impressed I am with the suspension.
 
Well today I installed the Cogent Dynamics DDC fork kit in my 21. NC750X. Works a treat! I had installed their kits in other bikes so I decided to give it a try in my NC. Super easy install, loosen top caps, remove fork legs, remove caps , springs and spacers, drain old oil, 1/2 in pan 1/2 on floor, leave forks upside down to drain rest of oil in pan, go buy some kitty litter, eat lunch. Return and clean up my mess. Added Cogent Dynamics supplied 10 wt oil to 130mm level, drop in new valve assembly into each tube, drop in new straight wound springs and spacers and reassemble.
The oil I drained on floor and pan seemed to have quite a lot of aluminum entrained. It was a dark gray color which surprised me on a 18 month old 5,000 mile bike. I will change the fork oil on the next tire change and see what’s up.
The newly modified forks are quite a bit better, the sharp jolt on pavement irregularly that was present is now either gone or greatly reduced. Before if I hit a little spot in the pavement when in a sweeping curve it would upset the balance and the front would try to step out when really pushed, now same situation the bike is way more stable.
When ordered the kit from Cogent Dynamics they ask a lot of questions to see how you ride, how much you weigh (I accused them of meddling), 2 up, luggage and what your expectations were. The kit they sent seems to be a close to perfect as possible for the bike and the way I ride it. Very satisfied, so now I will start allocating money for their hind shock.
 
Well today I installed the Cogent Dynamics DDC fork kit in my 21. NC750X. Works a treat! I had installed their kits in other bikes so I decided to give it a try in my NC. Super easy install, loosen top caps, remove fork legs, remove caps , springs and spacers, drain old oil, 1/2 in pan 1/2 on floor, leave forks upside down to drain rest of oil in pan, go buy some kitty litter, eat lunch. Return and clean up my mess. Added Cogent Dynamics supplied 10 wt oil to 130mm level, drop in new valve assembly into each tube, drop in new straight wound springs and spacers and reassemble.
The oil I drained on floor and pan seemed to have quite a lot of aluminum entrained. It was a dark gray color which surprised me on a 18 month old 5,000 mile bike. I will change the fork oil on the next tire change and see what’s up.
The newly modified forks are quite a bit better, the sharp jolt on pavement irregularly that was present is now either gone or greatly reduced. Before if I hit a little spot in the pavement when in a sweeping curve it would upset the balance and the front would try to step out when really pushed, now same situation the bike is way more stable.
When ordered the kit from Cogent Dynamics they ask a lot of questions to see how you ride, how much you weigh (I accused them of meddling), 2 up, luggage and what your expectations were. The kit they sent seems to be a close to perfect as possible for the bike and the way I ride it. Very satisfied, so now I will start allocating money for their hind shock.
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>> "Well today I installed the Cogent Dynamics DDC fork kit in my 21. NC750X."
The 2021 model has forks with Showa SDBV system. Does your bike have them? I didn't think that you could fit emulators to the SDBV forks.
 
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The 2021 model has forks with Showa SDBV system. Does your bike have them? I didn't think that you could fit emulators to the SDBV forks.
Yes, my bike is/was equipped with the Showa Bending Valve Fork. Cogent Dynamics said the bending valve arrangement was quite basic. The original valve remains in place and the Cogent Dynamics valve body is dropped into the tube. With the 10 wt oil the new dampner does the work and the original valve doesn’t have any effect . I very specifically ask Cogent Dynamics that very question and their technicians all agree that it was a proper installation. I replaced the progressive wound spring with their supplied straight wound spring and spacers. I can attest the forks work much better. My other rides are “dem fancy Italian jobs” so my suspension expectations are probably more demanding.
 
Yes, my bike is/was equipped with the Showa Bending Valve Fork. Cogent Dynamics said the bending valve arrangement was quite basic. The original valve remains in place and the Cogent Dynamics valve body is dropped into the tube. With the 10 wt oil the new dampner does the work and the original valve doesn’t have any effect . I very specifically ask Cogent Dynamics that very question and their technicians all agree that it was a proper installation. I replaced the progressive wound spring with their supplied straight wound spring and spacers. I can attest the forks work much better. My other rides are “dem fancy Italian jobs” so my suspension expectations are probably more demanding.
I ride solo and am only 165 lbs in riding gear. I found the Cogent Dynamics suggested 130 - 140 mm oil height was too progressive and left too much unused fork travel. I eventually settled on 150 mm. Mine is a 2013. The Cogent fork upgrade is the best bang for the buck I've ever spent on an NC.
 
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