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Update: Stock YZ450 w/ICS to full Dual Del Taco, etc.

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I just did a full update on the forks and shock using the stuff from Smart Performance, by Dave Johnson. Since then, I've had it out on a shake down run, a short ride, and a race day.

Previously, I had installed the softer ICS springs and drilled the free piston in the forks, along with using 215.VM2.K5 at both ends. In this upgrade, the fork got the EPNP dual ICS spring kit, the "cloverleaf" anti-cavitation base valve check plates, slight tweak of the base stack, and the Dual Spring "Del Taco" mid valve kit. The shock got the rebound stack modified. 215.VM2.K5 fluid was used all around, With SPI#5 in the outer chambers and SPI#3 everywhere else.

The first ride was at Lark Canyon/McCain Valley; DG soils, nice and wet from the rains, whoops from small to montrous, and sections of loose and embedded rocks ranging in sizes up to as big as a two-story office building. The next was about a 40 minute warmup ride, followed by a 1 hour Euro Scrambles in the desert.

I am not the sort of test rider who instantly picks up every detail of suspension operation, for one thing, and when using Dave's oil it does seem to take some time for the suspension to loosen up a bit.

But as I rode I started noticing stuff, like the fact that the fork was distinctly better in G-out situations like a downhill meeting an uphill right at the bottom without a lot of transition. I'm still not terribly impressed with the feel of the fork at lower speeds over smaller stuff, but it is better than it was, and when I look down and see what the wheel is really doing, I realize that I'm not feeling nearly everything that's going on. When you start to go a little faster, it's pretty amazing. At speed, the ability of this setup to absorb energy is uncanny. It takes almost all the impact out of any "normal" sized obstacles, and the big ones don't hit nearly as hard as I think they should. Control in rutted and whooped sand washes is much improved, and there is much less tendency for the front wheel to tuck and turn when it lands in the bottom of a hole in the soft stuff. Landing on flat ground front wheel first from a ten foot drop was completely uneventful.

At low speeds in rocks, even though I would still like it to feel plusher, it does track and steer better than it did with just the "Taco Sauce" and the softer ICS springs. The front end does not deflect off embedded rock of any reasonable size, and steering precision in that kind of stuff is much better. Even in loose rocks that rolled from under the wheel as I hit them, it was better.

As far as holding up for the length of a race, so far I haven't run it for longer than an hour, but within the confines of a single hour, it's noticeably better at the end than it is at the start, so I'm going to guess that the anti-cavitation mods are working.

I was pleased with the fork. It was pretty much as big an improvement as I thought it would be, especially at speed. The shock was a big surprise. Dave made a recommendation as to what the compression stack should look like for off-road applications, and since I found mine already like that, I left it that way. The HS compression, or exchange piston was modified to make it the same as the ones that come in the '08.

The rebound stack was changed by increasing the thickness of the first few shims at the bottom of the stack (against the piston). Dave's thought is that the Yamaha rebound stack is too loose initially. I questioned this at first, because with the stock stack, the bike was sensitive to rebound adjustment as far as cornering traction over rough ground was concerned, and I found that I was never happy with the compromise that had to be struck between the performance in the whoops and chop, and in cornering. Although I never found much fault with the compression side of things, it seemed to me that either the bike would skitter in the rough corners, or misbehave in the chop, and I could never get it to work right in the whoops no matter what I tried. The new stack fixed that completely.

The bike runs through whoops much flatter, and the fork seems to absorb more energy than ever. The rear does give the impression that it is settling, or "squatting" a little, but doesn't seem to be packing, and I could run through sections of whoops at Lark Canyon that are 3-400 yards long 10-15 mph faster than I ever felt comfortable with before. The rear wheel stays right behind the front, and doesn't kick at all as much as it did. It is very confidence-inspiring by comparison. In the desert, where the whoops are often unevenly spaced, or are off-square and you can't always get a rhythm going, this helps a lot. It also runs straighter in chewed up washes. This new stability at speed is perhaps the most impressive part of the job, and is very welcome. Of course, the fork has a lot to do with that, too.

Generally, the longer and faster I rode it, the better it got, and by the end of the race, I was running faster than I have in quite a while. Overall, I'm extremely pleased with the whole thing.

One other side note: Both the fork and shock have been running 215.VM2.K5 fluids since last May. When I took these apart, the oil looked to be in excellent condition, and was clean and clear looking. There were no signs of unusual wear anywhere that I could find.

Here are the settings I have ended up with so far:

Fork

C 16

R 13

325cc SPI#5 in outer chambers

SPI#3 inners

Shock

HS 2 out

LS 13

RB 8

SPI#3 oil

135psi nitrogen charge

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Good write up and I'm happy to see that you have very similar observations to mine, i.e., the shock settling in on whoops but not packing, 'feeling' the forks working in the small stuff but not deflecting, and the way the fork holds up to g-outs and high speed hits.

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Thanks for the write up. This is great to hear as I'm in the process of getting my pieces together to send to Dave.

Gray, just for a line in the sand as to your settings, would you be willing to share your skill level and weight?

Thanks,

Dave

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Gray, just for a line in the sand as to your settings, would you be willing to share your skill level and weight?

I am a mid pack expert desert racer well into the Super Senior class (50-59). I'm 180 in street clothes and I use stock springs.

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I am a mid pack expert desert racer well into the Super Senior class (50-59). I'm 180 in street clothes and I use stock springs.

Thank you, sir. No offence meant by the sir, as I believe you may have worked for a living in a previous life. :lol:

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Thank you, sir. No offence meant by the sir, as I believe you may have worked for a living in a previous life. :lol:

I'm at work now, trying to keep a network safe from its users.

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Thanks for the update.

So...when you get a chance let me know a little bit more about what you don't like on the front fork.

I mean, do you think this needs to be fixed or is it just something you feel in the parking lot?

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So...when you get a chance let me know a little bit more about what you don't like on the front fork.

Frankly, I'm inclined to think that it's mostly a matter of me having unrealistic expectations. I'll spend some more time with it and give you a better idea of what I mean once I can get a clear enough set of thoughts to coalesce in my head. I'll fiddle with the adjusters some more and see what effect that has on it, too.

The only complaint centers around the amount of shock felt at the grips while running at moderate speeds (30-45) over series of smaller bumps, such as a tracked-over sand dune, or a graded road that's mildly washboarded. As I said, when I look at the wheel during these times, it is very busy, moving vertically through a 2-3" range and following the ground well without skipping, and to see it, it doesn't surprise me that I feel it. I tend to think that the fork is so good with higher speeds and bigger obstacles that it makes me expect it to be smoother with the smaller stuff, but the two could be mutually exclusive. I should point out though that the fork is somewhat better in this regard than it ever has been, certainly better than stock, and it's by no means obnoxious.

If this were a customer coming to me with a pickup or a heavier car and complaining about harshness on rough pavement, I would cure it with a new set of Michelins, rather than expecting the suspension to be able to deal with it at all, if that gives you any sort of indication.

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Frankly, I'm inclined to think that it's mostly a matter of me having unrealistic expectations. I'll spend some more time with it and give you a better idea of what I mean once I can get a clear enough set of thoughts to coalesce in my head. I'll fiddle with the adjusters some more and see what effect that has on it, too.

The only complaint centers around the amount of shock felt at the grips while running at moderate speeds (30-45) over series of smaller bumps, such as a tracked-over sand dune, or a graded road that's mildly washboarded. As I said, when I look at the wheel during these times, it is very busy, moving vertically through a 2-3" range and following the ground well without skipping, and to see it, it doesn't surprise me that I feel it. I tend to think that the fork is so good with higher speeds and bigger obstacles that it makes me expect it to be smoother with the smaller stuff, but the two could be mutually exclusive. I should point out though that the fork is somewhat better in this regard than it ever has been, certainly better than stock, and it's by no means obnoxious.

If this were a customer coming to me with a pickup or a heavier car and complaining about harshness on rough pavement, I would cure it with a new set of Michelins, rather than expecting the suspension to be able to deal with it at all, if that gives you any sort of indication.

Ya know...I can't remember...did I ever give you instructions on changing the rebound stack?

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hhmmm interesting. have you the settings dave sent - or did he do the install.

im guessing you did it yourself as i know your technical abilities top notch.

im just wondering that you'd be better with the single stage mid, and two stage base. but i need to know whats in there.

sure dave will chime in though. :lol:

what oil volume did you run?

mark.

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Ya know...I can't remember...did I ever give you instructions on changing the rebound stack?
Shock rebound, yes. And as I say, the shock is much better for it.

Fork rebound, no modifications.

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Shock rebound, yes. And as I say, the shock is much better for it.

Fork rebound, no modifications.

yea...:lol:..at some point I think we need to adjust/change the rebound stack in the fork. I'm fairly certain that this is the solution to the problem that you are having.

Let me test a few things first, unless you want to jump in with some testing of your own, in which I'll provide a new stack for you.

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yea...:lol:..at some point I think we need to adjust/change the rebound stack in the fork. I'm fairly certain that this is the solution to the problem that you are having.

Let me test a few things first, unless you want to jump in with some testing of your own, in which I'll provide a new stack for you.

Either way. I'll contact you shortly about parts to do my son's bike, too.

Don't misunderstand regarding this "problem", OK? It is definitely NOT worse than it was.

I know you have something more sophisticated in mind, but in general, are you thinking that there is too much, or not enough rebound damping under these conditions (short stroke, rapid cycling)?

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Either way. I'll contact you shortly about parts to do my son's bike, too.

Don't misunderstand regarding this "problem", OK? It is definitely NOT worse than it was.

I know you have something more sophisticated in mind, but in general, are you thinking that there is too much, or not enough rebound damping under these conditions (short stroke, rapid cycling)?

Lighter. The rebound ramps up too quick, and it can't be resolved with the clickers. Mainly a problem with the washboard stuff.

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This is very interesting reading this thread...

I have just been on the phone with an expert level rider who has the DDT in his 09 YZ450F and he is having EXACTLY the same issue.

He has just raced the Finke Desert race and experienced very bad transmission through the bars on washboard type stuff and medium sized hits. I also rode the bike yesterday and it felt great on very small and very large hits but anything in between was occasionally a little harsh and unpredictable.

We discussed the possibility of making the fork rebound slightly lighter so I'll be interested to hear what you suggest. I cant remember the exact stack we have been running but ill double check later tonight.

Up until now he has been over the moon with this setup... he still thinks it is the best suspension ever and this is a relatively small issue, but one that we would like to solve anyway.

Dave.

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This is very interesting reading this thread...

I have just been on the phone with an expert level rider who has the DDT in his 09 YZ450F and he is having EXACTLY the same issue.

He has just raced the Finke Desert race and experienced very bad transmission through the bars on washboard type stuff and medium sized hits. I also rode the bike yesterday and it felt great on very small and very large hits but anything in between was occasionally a little harsh and unpredictable.

We discussed the possibility of making the fork rebound slightly lighter so I'll be interested to hear what you suggest. I cant remember the exact stack we have been running but ill double check later tonight.

Up until now he has been over the moon with this setup... he still thinks it is the best suspension ever and this is a relatively small issue, but one that we would like to solve anyway.

Dave.

Well, I'm 100% on the positon that the KYBs have way too much rebound in the fork, from the factory. We have alleviated a lot of complaints of "it's too harsh" by simply removing or de-tuning the fork rebound stack. Night and day difference.

Dell Taco or not, it has to be done, and running the 215.VM2.K5 with the factory KYB rebound stack only makes matters worse.

As for SHOWAs, they are perfect...and we don't touch them unless the spring is changed.

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i've been running all the del taco stuff for most of this season now, and have to say after a while i just got tired taking my forks apart lol. having said that, all the while i've been making progress. mark at spi europe has been great in trying to figure out why the kit hasn't been 100% for me.

i started off with all the gear inside to mark's settings, ddt, clover leaf, epnp etc.

the fork just felt perfect on any big fast impact. but on corner exit on choppy bumps just felt light and nervous and a little choppy. how would this rebound damping reduction affect this. i'm running 4.4n springs btw and 300ml outer level with decent bottoming control.

what level of reb shim adjustment are we talking?

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Well, I'm 100% on the positon that the KYBs have way too much rebound in the fork, from the factory. We have alleviated a lot of complaints of "it's too harsh" by simply removing or de-tuning the fork rebound stack. Night and day difference.

Dell Taco or not, it has to be done, and running the 215.VM2.K5 with the factory KYB rebound stack only makes matters worse.

As for SHOWAs, they are perfect...and we don't touch them unless the spring is changed.

for me, this reb. stack works realy well on my kxf 450/07.

20.11 2x

12.11

18.11

16.11

14.11

12.11

10.25

Stock Springs, 340ccm Oil Level on hard loamy tracks .( reb. is to soft for Sand and much higher Oillevel!):worthy:

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The majority of my kyb rebound set ups look like the above posted.

The new kawi 450 uses 5 (yes, 5!) face shims on the rebound side stock. Talk about way too slow!

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Well, I'm 100% on the positon that the KYBs have way too much rebound in the fork, from the factory. We have alleviated a lot of complaints of "it's too harsh" by simply removing or de-tuning the fork rebound stack. Night and day difference.

Dell Taco or not, it has to be done, and running the 215.VM2.K5 with the factory KYB rebound stack only makes matters worse.

As for SHOWAs, they are perfect...and we don't touch them unless the spring is changed.

What about in the shock on a showa MX model used for singletrack?

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