2008 yz450f trail suspension help


14 replies to this topic
  • Mark537

Posted April 30, 2012 - 06:05 PM

#1

I been playing with my bikes setup. I have set the sag and slid the forks up 5mm in the clamps. I rode a friends ktm and his suspension is much softer he has had his setup for a 140lb rider but his seemed so much smoother and plush. How do you start setting it up to become more plush like this?

  • RiderX

Posted April 30, 2012 - 06:59 PM

#2

If your friends KTM is an XCW/EXC or even an XC/MXC it will feel softer, because it's tuned for trails. Your YZF is tuned for MX. A revalve helps bigtime, but correct springs are a big start. Do you know if you have the correct springs for your weight in the woods?

  • Gunner354

Posted May 01, 2012 - 02:33 PM

#3

I been playing with my bikes setup. I have set the sag and slid the forks up 5mm in the clamps. I rode a friends ktm and his suspension is much softer he has had his setup for a 140lb rider but his seemed so much smoother and plush. How do you start setting it up to become more plush like this?

I weigh 175lbs and ended up leaving forks in stock position in triple clamps and backing off compression in forks to 20 clicks out. Rear is pretty much stock setting. It's now perfect for trail riding. Seems to be well balanced.

Edited by Gunner354, May 01, 2012 - 02:34 PM.


  • Mark537

Posted May 01, 2012 - 04:21 PM

#4

I weigh 175lbs and ended up leaving forks in stock position in triple clamps and backing off compression in forks to 20 clicks out. Rear is pretty much stock setting. It's now perfect for trail riding. Seems to be well balanced.


Ok i will give that a try. What sag are you running? I have mine at 100mm. I have to change fork seals and was thinking about putting a little less oil in the front forks. But before I try this I will try your suggestions.

  • Gunner354

Posted May 01, 2012 - 06:14 PM

#5

Ok i will give that a try. What sag are you running? I have mine at 100mm. I have to change fork seals and was thinking about putting a little less oil in the front forks. But before I try this I will try your suggestions.

I run sag at 100 mm. The backed off fork compression was a huge improvement!

  • grayracer513

Posted May 01, 2012 - 06:23 PM

#6

The backed off fork compression was a huge improvement!


That's pretty much the first thing to try, and not just the fork, either. 175 is within the range the bike was built for, so you shouldn't need springs. I weigh about that, and the stock rates work fine for me.

Back the fork compression all the way out to start with, and come out 2 turns or more on the shock HS comp. Back the rear LS comp out to at least 12-15, and set enough rebound to maintain control in rocky sections. Start from there and see what you want to do with it. Remember that the YZ is a purpose built MX bike, and doing stuff like backing off the fork compression that far wouldn't work unless it was.

  • LILBIT

Posted May 02, 2012 - 01:26 PM

#7

greyracer don't you find rebound control is lost with the shock's LS that soft combined with the HS that loose. I had to add HS on my bikes to avoid "kick" with the soft set up. If i went up on the rebound enough to gain control it packed up on multiple hits.

Throw a tie wrap on the forks to see how much travel you're using. If i run full soft the forks seem harsher than 2-4 clicks in because the forks blow through and gets hard on root hits.

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  • grayracer513

Posted May 02, 2012 - 03:42 PM

#8

greyracer don't you find rebound control is lost with the shock's LS that soft combined with the HS that loose. I had to add HS on my bikes to avoid "kick" with the soft set up. If i went up on the rebound enough to gain control it packed up on multiple hits.


It depends on how the bike is to be used. For moderate recreational trail riding, it's not a problem, but at higher speeds in an off-road environment, you have brought to light one of the stock shock's major shortcomings. The face of the OEM rebound stack is way, way too soft. If you're willing to compromise some things, the stock shock works OK, but stiffening the rebound stack at the face while adding a bleed shim to a modified HS stack has proven to work wonders for my own desert racer.

The kick in the rear on larger bumps at speed is from too loose initial rebound response. A good deal of the instability you feel in the front end over whoops at speed off road is caused by the rear as well, as I discovered when I made these changes in mine. When this is controlled, the rear stays down, and the bike goes straight. It's a beautiful thing.

When you hit a grapefruit sized rock going 15 mph up a canyon bottom, that's a high speed stroke in terms of how the shock works. By bleeding the HS some, what you're doing is delaying its reaction. The damping is still there, but it will allow short, quick stroke of the shock without kicking the rider around.

  • LILBIT

Posted May 03, 2012 - 03:47 AM

#9

Ok.
I do understand the front rear tuning relationship. If one ends fault is larger than the others it will be masked. I always find myself "fixing" one end only to feel faults in the other i hadn't noticed before.

I have wondered what are the signs of using too much HS? I find myself running more than average. Can't find a big downside but as you say i'm using it to compensate for the rebound issue. I do not normally as soft on the LS as mentioned above but less than the typical MXer.

  • grayracer513

Posted May 03, 2012 - 07:19 AM

#10

I do understand the front rear tuning relationship.... I always find myself "fixing" one end only to feel faults in the other i hadn't noticed before.


Yep, that's how it works. When I started with my '06, my impression was that I wished the fork was as good as the shock. After the first couple of phases with the fork, I could see the shock needed work, so I fixed that, and then found something else about the fork to monkey with. Of course, that meant more work on the shock. That's what makes suspension tuning both fun and frustrating. You're never really finished with it. :banghead:

I have wondered what are the signs of using too much HS? I find myself running more than average. Can't find a big downside but as you say i'm using it to compensate for the rebound issue. I do not normally as soft on the LS as mentioned above but less than the typical MXer.


Remember that the terms HS and LS refer to the speed at which the suspension unit moves, and has nothing to do with the speed of the bike, necessarily. Too much high speed results in a lack of compliance with stuff that moves the fork or shock very quickly, like a whoop crest at 40 mph, or the above mentioned rock at 15. How this affects the rider or his control depends entirely on the situation. The low bike speed rock strike will bounce you sharply up and probably to one side. The sharp edge out in the middle of nowhere at speed will kick the chassis up before the suspension can react.

The focus of the modifications I make to the high speed damping on either end are not really about reducing it as much as getting it not to react quite as quickly to lower amplitude strokes. That's the real key to getting plushness on smaller hack while retaining the ability to take the big hit. But, because of what they involve, it's just not something that you can do with the clickers or oil level adjustments.

  • LILBIT

Posted May 03, 2012 - 05:03 PM

#11

The shock shaft speed as you describe is what i understood from others regarding HS and LS. I have no experience with HS adjustability until recently having owned older bikes and KTMs up to '05s.

I started Yamahas with a stock '06 YZ 250t which i just handed down to my son and now have a very low hour '07 450f. I thought the 250 was a massive improvement but the 450 is another step forward. What has slowed my understanding is the 450 suspension is not stock. With stiffer springs (6.0 in the shock) it should be stiffer/rougher but i find it much plusher @ my 175 lbs. The biggest improvement on big hits and decel chop over the stock 250. The PO did not remember exactly what he did with the suspension. The bike sat for a while and he moved on to others.

Thank you for the replies.

  • grayracer513

Posted May 03, 2012 - 05:46 PM

#12

You're welcome. With a 6.0, I can see why you would have rebound problems. That's quite a bit of spring for someone your size (and mine). Interestingly, bikes that are long on spring and short on compression damping are often regarded as plusher than those of which the reverse is true. That will make sense if you think about it a while.

  • Mark537

Posted May 03, 2012 - 06:28 PM

#13

Thanks everyone for all of the help. I am heading out to test some of this tomorrow. I have a race on sunday so I want to get it feeling better before then.

  • blueberg17

Posted May 04, 2012 - 09:05 AM

#14

Not to high-jack your thread Mark... but I also have a 08 that I am trying to dial in the suspension.

Im 195lbs so I installed stiffer springs front and rear. The bike works better all around now for casual trail riding, jumping, etc with the stiffer springs and seems much smoother. Except for when I pick up the pace the front seems fall down out of my hands and the bounce back through rough sections; especially in deep whoops. where as before (w/ stock springs) I could more or less 'skip' across the top of the whoops..

Any suggestions?

Edited by Levi_M, May 04, 2012 - 09:22 AM.


  • LILBIT

Posted May 04, 2012 - 04:54 PM

#15

You're welcome. With a 6.0, I can see why you would have rebound problems. That's quite a bit of spring for someone your size (and mine). Interestingly, bikes that are long on spring and short on compression damping are often regarded as plusher than those of which the reverse is true. That will make sense if you think about it a while.

No need to think very long. I've made up my mind on this a while ago. Better to be over sprung than under.

As far as the 6.0 spring goes i don't have much if any more rebound issues with the over sprung 450 than i do with the 250. If the compression is turned up to "normal" settings the rebound settings are also more "normal". I just can't run MX settings for all of my offroad areas. Rougher and faster stuff it's fantastic.

Seems most companies make spring rate suggestions based entirely on weight but other factors must come into play. I'm just trying to understand how this relates to me.





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