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Question YSS Front Suspension

mzflorida

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I ordered the YSS Front Fork Upgrade Kit from EPM Performance after having a conversation with the folks there about what I was trying to achieve. It comes with springs, spacers, fork caps that allow for preload adjustment, and a cartridge emulator. EPM Performance folks say that in the latest iteration of this product there is no need to add the two additional 8MM holes and YSS has removed that from their installation procedure. They also said that they have received zero complaints about this new design. However, he qualified that they are selling a lot of these kits for 21 and later and have sold fewer for the previous model years. Here is my question. Should I still drill the additional 8MM holes despite the change made by YSS? I've learned a lot more about suspension over the past couple of years but still am a novice so I appreciate any input.

Though not directly related to the above, I also ordered a Hyperpro rear shock with remote preload adjuster. EPM Performance give us veterans a pretty generous discount.

Thanks.
 

670cc

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Oil is apparently not included in the kit. What oil viscosity does YSS recommend? If a cartridge emulator is placed on top of the damper tube, but the stock damper tube holes are left unchanged, and the stock oil weight is used, all you can get from that arrangement is a more highly damped fork. If YSS says not to drill out the holes, are they recommending lighter viscosity oil?

Are the new spring‘s rates custom matched to the rider weight?

The question I’d have for YSS, is what does their kit hope to achieve? Without more information, I get the initial impression they are going for a taut, racing style performance.
 

mzflorida

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The instructions indicate a 20w oil is to be used. So heavier than OEM recommendation/specifications.

I believe the springs are set for my weight and riding style as they gathered that during my call. I’ll confirm.

The reviews I’ve read on the YSS suspension have described it similarly to your thoughts, firm but compliant with a substantial improvement in overall ride quality. However, those reviews I believe drilled the additional holes.

I’m leaning toward drilling and just ordering 2 damping rods to have them on standby. The drilling won’t cause a failure.
 

halfSpinDoctor

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Drilling the damping rod was no big deal. The main annoyance was the fact that I didn't have the correct length Allen wrench/key to undo the two bottom bolts (it's kind of a reach so you need "medium" or "long" Allen sockets), and then when I jerry-rigged something together it slipped and messed up the bolt head, meaning I had to wait an extra week to order that and get it all back together.

Looks like those damping rods are ~$40 ea. I guess that is not so bad, although it does substantially increase the overall cost of the mod.
 

670cc

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The instructions indicate a 20w oil is to be used. So heavier than OEM recommendation/specifications.

I believe the springs are set for my weight and riding style as they gathered that during my call. I’ll confirm.

The reviews I’ve read on the YSS suspension have described it similarly to your thoughts, firm but compliant with a substantial improvement in overall ride quality. However, those reviews I believe drilled the additional holes.

I’m leaning toward drilling and just ordering 2 damping rods to have them on standby. The drilling won’t cause a failure.
Not drilling the damper holes, adding an oil restriction on top of the damper pipe, and switching to thicker oil sounds like a recipe for an over damped, stiff front end. ”Firm but compliant” sounds like an oxymoron, or marketing mumbo jumbo. If you have very smoothly paved roads where you ride and the suspension never needs to handle bumps, maybe this is right for you, but it sounds like it wouldn’t work for me.

For the RaceTech emulators I installed, I drilled out the damper tube, while adding two additional holes per instructions, and set the emulators to about the least restrictive settings, and I’m using SS-8 or stock SS-47 “10 weight” oil. My forks are bump compliant except for a little stiction, and I don’t consider them at all to be too soft. I rate ride comfort to be more important than performance handling.

dduelin is an expert on NC forks, so hopefully he will give some opinions on this YSS offering.
 

mzflorida

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Drilling the damping rod was no big deal. The main annoyance was the fact that I didn't have the correct length Allen wrench/key to undo the two bottom bolts (it's kind of a reach so you need "medium" or "long" Allen sockets), and then when I jerry-rigged something together it slipped and messed up the bolt head, meaning I had to wait an extra week to order that and get it all back together.

Looks like those damping rods are ~$40 ea. I guess that is not so bad, although it does substantially increase the overall cost of the mod.
Thanks Doc. I think I’m going to drill them. I found the damping rods for $23.00 this morning. Nothing has changed on their design. Besides, tinkering is one of my favorite things to do. If I need to do it over it won’t be a big deal.

Mike
 

mzflorida

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Not drilling the damper holes, adding an oil restriction on top of the damper pipe, and switching to thicker oil sounds like a recipe for an over damped, stiff front end. ”Firm but compliant” sounds like an oxymoron, or marketing mumbo jumbo. If you have very smoothly paved roads where you ride and the suspension never needs to handle bumps, maybe this is right for you, but it sounds like it wouldn’t work for me.

For the RaceTech emulators I installed, I drilled out the damper tube, while adding two additional holes per instructions, and set the emulators to about the least restrictive settings, and I’m using SS-8 or stock SS-47 “10 weight” oil. My forks are bump compliant except for a little stiction, and I don’t consider them at all to be too soft. I rate ride comfort to be more important than performance handling.

dduelin is an expert on NC forks, so hopefully he will give some opinions on this YSS offering.
Thanks 670! The springs are bike specific not set for weight.
 

mzflorida

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Oil is apparently not included in the kit. What oil viscosity does YSS recommend? If a cartridge emulator is placed on top of the damper tube, but the stock damper tube holes are left unchanged, and the stock oil weight is used, all you can get from that arrangement is a more highly damped fork. If YSS says not to drill out the holes, are they recommending lighter viscosity oil?

Are the new spring‘s rates custom matched to the rider weight?

The question I’d have for YSS, is what does their kit hope to achieve? Without more information, I get the initial impression they are going for a taut, racing style performance.

I may have used the wrong term with “firm.” I’ve not found negative reviews and was earnestly searching. But, they all drilled.
 

670cc

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I may have used the wrong term with “firm.” I’ve not found negative reviews and was earnestly searching. But, they all drilled.
Well just for reference, the Cogent emulators do not require drilling the damper tube, but the way they are able to do that is they switch you to, I believe, 5 weight fork oil, which is lower viscosity than stock.
 

mzflorida

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Well just for reference, the Cogent emulators do not require drilling the damper tube, but the way they are able to do that is they switch you to, I believe, 5 weight fork oil, which is lower viscosity than stock.
Well, oil is cheap, damping rods are cheap, forks are easy to work on so I guess I can do a little experimenting. I have another question. I read somewhere, actually more than one source, that fork oil viscosity is rated differently across brands. I don't know if it is true. But, YSS is recommending their brand of fork oil (self-interest I'm sure) and I'm wondering if their 20W is actually a 10 or lower.
 

mzflorida

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Well just for reference, the Cogent emulators do not require drilling the damper tube, but the way they are able to do that is they switch you to, I believe, 5 weight fork oil, which is lower viscosity than stock.
Forgot to say thanks for taking the time to help me out!
 

670cc

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Well, oil is cheap, damping rods are cheap, forks are easy to work on so I guess I can do a little experimenting. I have another question. I read somewhere, actually more than one source, that fork oil viscosity is rated differently across brands. I don't know if it is true. But, YSS is recommending their brand of fork oil (self-interest I'm sure) and I'm wondering if their 20W is actually a 10 or lower.
Yes, it is known that fork oil viscosity ratings or definitions can be somewhat inconsistent across fork oil brands. That is why I earlier described Honda SS-47 as “10 weight” in quote marks. Still, it is difficult to imagine one company’s or vender’s 20 weight to be the equivalent of another’s 5 weight.

There was and maybe still is a web site where fork oil viscosities were compared against their claim and against each other. I don’t currently have a link to those results.

In the end, you are correct that you can adjust the outcome of the modification by making changes as you see fit.
 

dduelin

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Without knowing more than that which is in this thread I agree that a "20w" fork oil has too much viscosity to use if the stock rod dampers are retained.

Very light oils do not align well with the commonly used SAE standard of "weight". The best way to compare and choose fork oils is to use the ASTM figures called Viscosity (ISO) which uses a value of cSt at 40 degrees centigrade and VI which is Viscosity Index across a temperature range. Common fork oils have cSt values from about 5 cSt to 100+ cSt. Cartridge forks use cSt of about 15 and rod damping forks use about 34 cSt oil. Googling "fork oil chart" brings up a variety of lists or charts of common fork oils listing their values. I use this one and it includes a lot of information in addition to a list of oils:


It becomes easy with cSt and VI to pick out an oil to use or compare between oils. For example Cogent Dynamics suggests using Golden Spectro Cartridge Fluid 85w150 which is valued at cSt 16.9 and VI of over 100. Forks don't heat up much in use unlike shocks so any VI figure of 100 or more is generally OK. The factory oil in 700s is Showa SS-47 with a cSt of 35.2. Used in a cartridge fork or cartridge emulator SS-47 would be too thick and the fork would be very harsh, more so than stock. A comparable oil to Golden Spectro 85w150 would be Honda's Showa SS-5 with a cSt of 15.7.

I couldn't find anything online about YSS fork oils. Their fork kits offer K-Tech and Motul oils. If we could zero in on the brand and type of oil we could find out the cSt for comparison.
 

MZ5

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I'll agree with and reinforce what dduelin said about viscosity:
Look ONLY at the viscosity at 40 degrees C, plus the viscosity index, for fork oil. Disregard the marketers' so-called weight or grade numbers entirely. They're meaningless and distracting.

I typically use Red Line's suspension fluids because their viscosity indices are sky-high, which means there's very little change in damping rates as temperature changes. Again, not massively important in a fork, but for my own use I see little or no reason to purposely choose a low-VI fluid.

BTW, you can mix fork oils to get the viscosity you desire. I would personally stick to mixing only the same brand's fluids, but you can mix them. In Wiley, I typically run a mix of Red Line's Medium and Heavy products with my RaceTech Gold Valves. However, I had a shop do some work for me that I was unable to do at one point, and they put in a... Spectro? ...product. The forks still felt better for the fluid change, but different than what my mix gave.
 
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mzflorida

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Without knowing more than that which is in this thread I agree that a "20w" fork oil has too much viscosity to use if the stock rod dampers are retained.

Very light oils do not align well with the commonly used SAE standard of "weight". The best way to compare and choose fork oils is to use the ASTM figures called Viscosity (ISO) which uses a value of cSt at 40 degrees centigrade and VI which is Viscosity Index across a temperature range. Common fork oils have cSt values from about 5 cSt to 100+ cSt. Cartridge forks use cSt of about 15 and rod damping forks use about 34 cSt oil. Googling "fork oil chart" brings up a variety of lists or charts of common fork oils listing their values. I use this one and it includes a lot of information in addition to a list of oils:


It becomes easy with cSt and VI to pick out an oil to use or compare between oils. For example Cogent Dynamics suggests using Golden Spectro Cartridge Fluid 85w150 which is valued at cSt 16.9 and VI of over 100. Forks don't heat up much in use unlike shocks so any VI figure of 100 or more is generally OK. The factory oil in 700s is Showa SS-47 with a cSt of 35.2. Used in a cartridge fork or cartridge emulator SS-47 would be too thick and the fork would be very harsh, more so than stock. A comparable oil to Golden Spectro 85w150 would be Honda's Showa SS-5 with a cSt of 15.7.

I couldn't find anything online about YSS fork oils. Their fork kits offer K-Tech and Motul oils. If we could zero in on the brand and type of oil we could find out the cSt for comparison.
Thank you so much Dave. I’ll do some research and post here. Very much appreciate your time and detail. Lunch is on me if we have the meetup.

So if I’m inferring anything it would be to go with a lighter oil before considering drilling. Is that correct?
 

mzflorida

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I'll agree with and reinforce what dduelin said about viscosity:
Look ONLY at the viscosity at 40 degrees C, plus the viscosity index, for fork oil. Disregard the marketers' so-called weight or grade numbers entirely. They're meaningless and distracting.

I typically use Red Line's suspension fluids because their viscosity indices are sky-high, which means there's very little change in damping rates as temperature changes. Again, not massively important in a fork, but for my own use I see little or no reason to purposely choose a low-VI fluid.

BTW, you can mix fork oils to get the viscosity you desire. I wouldn't personally stick to mixing only the same brand's fluids, but you can mix them. In Wiley, I typically run a mix of Red Line's Medium and Heavy products with my RaceTech Gold Valves. However, I had a shop do some work for me that I was unable to do at one point, and they put in a... Spectro? ...product. The forks still felt better for the fluid change, but different than what my mix gave.
Thanks a million for taking the time to respond!! Very interesting.
 

mzflorida

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I found this thread. https://forum.classicmotorworks.com/index.php?topic=29997.15

The contributors suggest that removing drilling in the kit instructions is to make the installation more approachable to consumers who are going to self install. Supporting that, the damping valve can be purchased independently and is the same as the one in the kit. When purchased independently the instructions for the valve do say to drill. They might be correct in their opinion.

I found this regarding the recommended 20W YSS fork fluid at this location
https://speedmottorad.com/product/fork-fluid-fo20w-x/

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
 

670cc

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I found this thread. https://forum.classicmotorworks.com/index.php?topic=29997.15

The contributors suggest that removing drilling in the kit instructions is to make the installation more approachable to consumers who are going to self install. Supporting that, the damping valve can be purchased independently and is the same as the one in the kit. When purchased independently the instructions for the valve do say to drill. They might be correct in their opinion.

I found this regarding the recommended 20W YSS fork fluid at this location
https://speedmottorad.com/product/fork-fluid-fo20w-x/

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
It might help the relevance of replies in this thread if you described what you are trying to achieve with the fork modification. Do you want a taut race track suspension, a plush touring ride, or similar to stock without the harsh response on sharp bumps? From what I see so far, the YSS kit as installed per their directions is going to give you a stiff front fork. For all I know, perhaps that’s what you want.

I find it hard to see how deleting the drilling procedure just to “make the installation more approachable” is going to deliver anywhere close to the same results.
 
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mzflorida

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It might help the relevance of replies in this thread if you described what you are trying to achieve with the fork modification. Do you want a taut race track suspension, a plush touring ride, or similar to stock without the harsh response on sharp bumps? From what I see so far, the YSS kit as installed per their directions is going to give you a stiff front fork. For all I know, perhaps that’s what you want.

I find it hard to see how deleting the drilling procedure just to “make the installation more approachable” is going to deliver anywhere close to the same results.
Similar to stock but moving a little closer to plush. I do think the front end chatters far too much.

I am unsure if I understand your second point. I believe the other post I shared suggests that drilling is required to achieve the intended results of an improved suspension, whereas omitting that modification would produce less than desirable outcomes. Is that what you are getting at?

I did not go back and review the post but being more approachable might be my words. In other words, many self-installers may be afraid to drill the rods or don't have access to a machine shop which could reduce sales by introducing steps which are inaccessible or beyond the abilities of the prospective purchaser.
 

670cc

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Similar to stock but moving a little closer to plush. I do think the front end chatters far too much.

I am unsure if I understand your second point. I believe the other post I shared suggests that drilling is required to achieve the intended results of an improved suspension, whereas omitting that modification would produce less than desirable outcomes. Is that what you are getting at?

I did not go back and review the post but being more approachable might be my words. In other words, many self-installers may be afraid to drill the rods or don't have access to a machine shop which could reduce sales by introducing steps which are inaccessible or beyond the abilities of the prospective purchaser.
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.
 
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