Ive ridden a few different bikes over the years:
2009 CRF450r - suspension was clapped because the fork cartridge seals were custom machined from a BMG seal jet machine and were too tight but i had no reference, i was too poor for mx bikes at this point in time.
2014 CRF450r - These were air forks, they felt much better but reference was lacking
2020 Yz450f - Mind blown, never felt such plush suspension in my life. I recall the first day i went riding super clearly. Went to a rut track in the bush close to my house and hit a turn that had some hard sun baked braking bumps going into the turn. I expected the bike to blitz the bumps and have the back wheel wander left and right so i gripped hard with my legs to keep the bike straight and the wheels didn't even leave the ground they just tracked perfectly. Gave me the the feeling of, oh wow i went way to slow there, and i would go faster and faster to a point where i was so impressed at how the back wheel would just stay planted and not bounce out the run on the entrance. The feeling on my front was also so plush, no square edge feeling from what i was use to with the previous air forks. overall was life changing!!!
2015 YZ250 - At this point i had the s troke and the 450r. the 250 had a good setup but was abit too soft. Would turn great though. Plushness was on point. I put in gold valves with A rider shim stack from race techs website and the suspension was really nice. one think i liked about this was the initial hit was so so soft and the damping would ramp up in a way that once the suspension starts getting close to end of stroke it would damp really hard but in a plush comfortable way. Hard to explain but i yearn for this feeling again.
2022 YZ450f - Really good. Was starting to race mx1 in south africa at this point, even though i was coming 2nd last but was the peak of my riding and i was super comfortable with my suspension. Had my front and back revalved slightly harder and was on one spring rate harder for my weight. Bike was super uncomfortable especially in braking chop but i could charge really hard out of turns without harshness. I recall one race there was a huge square edge out of a rut that i would normally avoid but with the setup i had, i could sit under full power into this edge and there was no shock or harshness at all, it soaked it up so well.
2022 FC450 - Front forks were really harsh, going back to air i think i had some placebo stigma about air at this point but the bike got stolen before i could even have it run in. I also had not ridden for a full year at this point so i had become pretty soft and fragile
2023 YZ450f - This is where my question comes. I was expecting the feeling of atleast my 2020 YZ450f but nope, the bike felt really stiff since new, i knew i had to put atleast 15hours on the suspension to get it nice and run in. But the stiff feeling never left. After replacing bushings and seals and now at 40 hours the bike still feels like shit. When i land on flat there is a shock that comes through my hands as if im running air forks. Nothing like the SSS i remember. The back shock also transfers a lot of shock while accelerating out of turns to the point where it feels like my hands will blow off the bars and my kidneys are getting lacerated from tearing. I have been riding a lot again at this point and would say im quite fit and strong again but i still feel its very harsh. Im 78kg naked and probably around 82-83kg with all my gear on. Running stock setup. tested the spring and its a 53 N/mm spring. The bike balance feels good at 100mm of sag but i have tried running 95mm of sag and the harshness is still there. I have ordered a 55N/mm back spring for the back so will test that.
I guess im curious to hear your take on how the KYB stuff on the yz450f has changed over the years?
The short answer:
What you are feeling is mostly in the shims, springs, oil and clicker settings.
The rest can be attributed to the chassis your suspension is bolted to.
In my opinion, suspension has been trending toward stiffer springs and more damping over the last 10 to 15 years.
Also, some of these manufacturers have gone toward stiffer frames and more aggressive geometry.
A more flexible frame and soft suspension can have comfort at lower speeds for just about anyone. As the chassis & suspension both become stiffer, setup becomes more critical, but you can go faster when it is dialed.
Technically the correct name for all of these KYB forks is AOS... Yamaha uses SSS as their marketing term, but the components are essentially the same.
KYB AOS cartridges used in 48mm forks from 2006 up through 2017 from any make & model are functionally the same. They all used a 24mm mid valve piston with a 12.5mm rod. In 2018 Yamaha increased the mid valve diameter to 25mm on the YZ450F. The YZ250F got the 25mm piston in the 2019 model. The valving and chassis worked really well together from 2018 - 2022. The 2023+ chassis has been criticized as a step backward in comfort and handling. I believe it is stiffer and has a steeper head angle than the 2022 and has been changed again from 2023 to 2026.
Kawasaki and Honda used similar KYB AOS forks from 2009 - 2012 on their 450cc models, but the valving, spring rates and oil volumes were not as well selected as Yamaha's stuff. What Yamaha does really well is develop a complete suspension setting for their chassis.
The only significant difference between the 24mm cartridges used in those older KYB forks is the type of mid valve. If you've heard of "leaf spring" or "trampoline spring" mid valve, that's the major difference. Yamaha used conventional mid valve float (very light coil springs) until they introduced the 25mm cartridges in 2018. Kawasaki had leaf spring mid valve setups in 2011 - 2012 forks. Any KYB AOS cartridge can be converted to leaf spring mid valve with some inexpensive parts, a handful of shims and some know-how.
I manufacture KYB conversion kits for the KTM air forks and I use them on my own race bike. https://dialedmfg.com/technical-information.html
One set of forks I race with has 2012 KX450F cartridges in them. Another set has 2021 YZ250F cartridges.
Both sets have significant valving changes to suit my 350F, my riding style, terrain, etc. Currently, I have a better setting in the older 24mm cartridges because I've spent so much more time trying to get the best comfort from them. I'll spend a little more time on some 25mm stuff in the new year.
Oh wait so are you saying the 2023 yz450f does not use the float style midvalve anymore?
That's right.
Yamaha switched the four stroke models to leaf spring mid in 2018 and 2019 when they increased the cartridge size to 25mm.
You can convert any of the older cartridges to leaf spring.
Search my posts from a few years back... I did a little write up on how I set up my YZ125, YZ250 and KX500.
I've found that most off-road guys dislike the leaf spring setup.
They want a much softer suspension and are willing to trade hold-up to get comfort.
Can you convert the newer 25mm leaf spring back to float style?
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Yes, you have to come up with the little coil spring.
The cup is integrated into the MV post and it's only about 0.8mm deep, so it's not as well suited to the task as the conventional float cup.
Also, the slide-collar is integrated into the post.
Also, you can make a pretty light leaf spring with a single 20mm x 0.1mm shim on the cup followed by a 10mm x 0.3mm shim. That's not as light as the conventional float, but I doubt most riders could tell the difference.
I've thought about trying some two stage leaf springs for off-road stuff and slower vet guys... It would look like below...
[PISTON]
[TYPICAL MV STACK]
11x0.30
12x0.1
14x0.1
16x0.1
18x0.1
20x0.1
20x0.1
10x0.2 (10mm shim creates a two stage system)
20x0.1
13x0.3 (limit shim gives 0.5mm total float)
[INTEGRATED CUP & POST]
Sweet thanks for the info ill try this for sure.
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