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Fork rebound, emulators, Yss, etc.?

B

boardhauler

Well travelled
Location
US
My front fork is stock, 11,000 miles on it and the oil. I have recently noticed a lot of rebound noise on small washboard roads and the like. It rides harsher at the top out of travel. Has anyone installed the YSS or similar valves and successfully remedied this? Or should I just change the oil?
 
Alan F. said:
I've heard factory oil levels can vary a lot, even from left to right fork. I'm sure you'll get lots of replies but starting simple might be advisable.
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That is a fair point, however it has only started recently. Possibly my oil is breaking down and becoming thinner? As rebound dampening is controlled by a tiny hole in the inner fork tube.
 
I drilled out my fork pistons at the bottom ( as per YSS instructions) leaving the small rebound damping hole alone, shortened the upper spacer tube and fitted the YSS emulators, keeping the stock springs. I also fitted CooperB fork extensions with preloaders. After a lot of strip down and adjustments eventually settled on 10W oil at 460ml, 3 turns on the emulators, and approx 6mm of preload. Really pleased with this set up, it really works for me and potholes & huge unmarked speed breakers on Indian roads, never tried it on washboard though
 
Having said all of that, for simplicity try changing your oil and experiment with different oil levels, I changed oil weights and oil levels 5 times before I settled on 460ml 10W oil ( admittedly with emulators). Suggest your base point with stock pistons be 15w oil at 455ml and just add 5ml at a time till you find what works for you...I went as high as 470ml but came back down to 460ml.
 
boardhauler said:
That is a fair point, however it has only started recently. Possibly my oil is breaking down and becoming thinner? As rebound dampening is controlled by a tiny hole in the inner fork tube.
Click to expand...

Eatmore Mudd put me on the spot, but....

Fork oil takes a very long time to "break down". Your recent noticing of the suspension is probably due to getting used to the horrible stock response - it really is terrible. YSS fork parts don't provide much improvement over stock and some have said they're even worse than stock.

RaceTech emulators and springs are the way to go. Yes, they're expensive, but the stock front suspension is straight out of early 1960's technology, so fixing it will require some investment. One way is very expensive (replace the entire fork leg assembly with something from Ohlin, K-Tech or Bud) or go to the RaceTech website, work through the worksheets (yeah its shrouded in mystery and a PITA), and order the parts they suggest. I guarantee it'll improve things. Modifying (destroying) the stock internals will take a strong stomach, but realize they are cheap and it will improve things!

If you decide to do this, I have a tool I made for for fork dissassmebly/assembly that I'll loan to anyone in need (free plus shipping).
 
OldGuy said:
Eatmore Mudd put me on the spot, but....

Fork oil takes a very long time to "break down". Your recent noticing of the suspension is probably due to getting used to the horrible stock response - it really is terrible. YSS fork parts don't provide much improvement over stock and some have said they're even worse than stock.

RaceTech emulators and springs are the way to go. Yes, they're expensive, but the stock front suspension is straight out of early 1960's technology, so fixing it will require some investment. One way is very expensive (replace the entire fork leg assembly with something from Ohlin, K-Tech or Bud) or go to the RaceTech website, work through the worksheets (yeah its shrouded in mystery and a PITA), and order the parts they suggest. I guarantee it'll improve things. Modifying (destroying) the stock internals will take a strong stomach, but realize they are cheap and it will improve things!

If you decide to do this, I have a tool I made for for fork dissassmebly/assembly that I'll loan to anyone in need (free plus shipping).
Click to expand...

Bang !! and just like that......
Thank you for helping him out.
I couldn't have summed it up like that. I owe you lunch.
 
OldGuy said:
Eatmore Mudd put me on the spot, but....

Fork oil takes a very long time to "break down". Your recent noticing of the suspension is probably due to getting used to the horrible stock response - it really is terrible. YSS fork parts don't provide much improvement over stock and some have said they're even worse than stock.

RaceTech emulators and springs are the way to go. Yes, they're expensive, but the stock front suspension is straight out of early 1960's technology, so fixing it will require some investment. One way is very expensive (replace the entire fork leg assembly with something from Ohlin, K-Tech or Bud) or go to the RaceTech website, work through the worksheets (yeah its shrouded in mystery and a PITA), and order the parts they suggest. I guarantee it'll improve things. Modifying (destroying) the stock internals will take a strong stomach, but realize they are cheap and it will improve things!

If you decide to do this, I have a tool I made for for fork dissassmebly/assembly that I'll loan to anyone in need (free plus shipping).
Click to expand...
Thank you. Great, I'll look over the RaceTech page. It looks like any cartridge emulator (YSS or RaceTech) will allow me to tune rebound by allowing compression dampening adjustment via it's valve. Freeing up the oil to be changed to a slightly higher viscosity to effect rebound.

I have seen postings of a few who have changed oil weight after installing emulators. I was hoping for some comments on how it did or did not change rebound dampening. Anyone?
 
I started with 15w oil and settled on 10w with the yss emulators at 3 turns, the Race Tech emulators and spring options look better as they can have different strength springs based on weight and usage looking at their website. Pricey though.
I felt the rebound damping was too slow with 15 w, feels much better with 10w, wouldn't want to go down to 5w as probably not enough damping and a bit to bouncy for my liking. I'm happy with my set up, but that doesn't mean I won't continue to play with it, looking for a secondhand set of forks to make/ allow easier ongoing changes, thnking spring rates, spring types, even alternative weight springs on the yss emulators, reckon I can do all of those things fairly cheap if I get creative in India.
 
I went with the oil and amount RaceTech recommends - IIRC it's 10W. Compression and rebound damping is not really adjustable with the RT emulators. The adjusters are set per their instructions and they warn against making any changes. I like the way they work at this point, which is far better than stock. And at least RT will make sure you get springs that fit you and your riding style.

The only real adjustment is oil and preload if you install adjusters. But preload only sets loaded ride height and has no effect on damping.

But lets face it, like I said before, you can't turn a farm tractor into a factory MX'r. Unless you replace the entire fork assembly, it'll never be great - only acceptable.
 
Gamphy said:
I started with 15w oil and settled on 10w with the yss emulators at 3 turns, the Race Tech emulators and spring options look better as they can have different strength springs based on weight and usage looking at their website. Pricey though.
I felt the rebound damping was too slow with 15 w, feels much better with 10w, wouldn't want to go down to 5w as probably not enough damping and a bit to bouncy for my liking. I'm happy with my set up, but that doesn't mean I won't continue to play with it, looking for a secondhand set of forks to make/ allow easier ongoing changes, thnking spring rates, spring types, even alternative weight springs on the yss emulators, reckon I can do all of those things fairly cheap if I get creative in India.
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Did your fork "pack up" from slower rebound with the 15 weight oil? With multiple bumps in succession, was it not recovering height quick enough. I was thinking of blending 10 and 15 to get a mid weight. It looks like a small change in oil should make a difference in the rebound as it travels through just one tiny hole.

Also, I just realized the only change I have made to my fork is most likely effecting the top out harshness, my preload fork caps are on their lowest setting, however they added some preload over the stock caps and spacer that I replaced. At my weight (185 lbs wo gear] I didn’t think it would make such a difference, but it does! When I carefully measured the fork sag, it is slightly less than ideal. So, I think I have pushed myself into a fork rebuild. I can add emulators, cut down the spacer to allow the preloaders room, replace the boots and oil.
 
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I found on two of my RE's (haven't done Pyle yet), that simply changing the fluid to a quality a 10w (I think i used Maxima last time), with the proper air gap, with adjustable fork caps, made a definite difference. That said, I don't ride hard anymore, but our roads are crap. It removed a bunch of the "elbow/wrist harshness" from the ride when I hit potholes.
 
I didn't experience the forks ' packing' mainly because I ride rough roads, not washboard or whoops. But changing the oil down to 10w + an extra 5ml ,made the forks react a little quicker and smoother. That is with drilled out pistons and yss emulators. Ultimately like Old man says, unless you change the forks they are always going to be old tech and will never be anywhere near as good as modern MX forks, if you're in the States, I would follow Old man's advice and go down the RaceTech emulators and springs route as they provide spring rates based on you, not just generic.
 
Per Oldguy's recommendation I checked out the Racetech webpage. They have a nice calc for spring selection. It looks like they have another one that you have access to after buying the emulators to set them up. I found a video that shows how it works. I now understand why they are twice the cost of YSS.

 
I figured out that I definitely have too much preload today. After many miles off road, it’s topping out too fast. Seems I upset the Harris’ balance. I may just reduce it and change to oil.
 
Set the preload by setting the loaded ride height, not by feel or how fast it tops out. You have to be sitting on the bike with the load, front and back, that you intend to ride with, you included. You really need someone to help with this.

Here's the way you do it:
https://www.dirtrider.com/features/understanding-your-suspension-sag/

That's all preload does and all it's designed to do. Everything else is about the spring rate and damping.
 
OldGuy said:
Set the preload by setting the loaded ride height, not by feel or how fast it tops out. You have to be sitting on the bike with the load, front and back, that you intend to ride with, you included. You really need someone to help with this.

Here's the way you do it:
https://www.dirtrider.com/features/understanding-your-suspension-sag/

That's all preload does and all it's designed to do. Everything else is about the spring rate and damping.
Click to expand...
Preload is set as low as possible. Problem is, the new caps won’t back off enough. Have too much preload built in. I’ll probably mod them.

With tool little preload, it bounces off the top out, not enough throw to soak up the drops in the path.
 
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