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watto983

15 yzf 450 front end knifing

23 posts in this topic

Hey guys, just picked up a new 15 yzf 450 and absolutely love it. Only thing im struggling with is a feeling the front end is wanting to wash out and knife in soft corners. Even in straight line boggy conditions the front is very nervous. Im a 200 pound rider and running a rider sag of 105 with the forks up the clamps 4mm. Bike is bone stock including the MX52 front tyre which probably isn't helping in the softer stuff. I appreciate any help you guys could give. Thank you.

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At 200 lb, you're a bit heavy for the bike.  If you're knifing, or "tucking under", I'd start by running your forks back down in the clamps to the zero position and try that.  Add just a bit of compression to slow the dive going in, and don't run too much rebound damping (too slow). 

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I dont think this bike is undersprung. It has like.50 front springs and 5.8 rear which is pretty stiff. Ive got the 16 and they went down to 5.6 on the rear and it still is firm for me 200 lbs. Havent bottomed it out so far on like 70 ft doubles. Seems almost perfect suspensionwise so far. The steering is a little wishy washy. Raising the forks help. I run 100 sag. Im definitely no expert on the matter however. Still figuring out the setup. May try some 22mm clamps. The 16 went to 25mm! Kinda strange move I think.

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Yeah i was skeptical when i read they went to 25mm, I've heard mixed reactions. Most have gone back to the 22mm clamps. Thanks for the feedback, might put the forks back flush and play with the rebound and compression settings.

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It depends why you are 'knifing'.

 

If you are getting to much weight transfer to the front when braking , you will break front wheel traction and understeer. You would add a few compression clicks to the front, to keep the bike more level. 

This may transfer weight to the rear, creating additional front rake, so you would probably have to add some compression to the rear at the same time...

 

That is why GR mentioned spring rate. 

You mentioned race sag , but what about static sag?  Can you get 105 with 30 or less static? Preferably 25?

If you static sag is low, then the spring is under too much tension in the rear, transfering weight to the front too quickly.

 

If you do need to change the spring, you need to do the front at the same time.

 

 

 

If you are getting too much front wheel suspension 'action', then you need to slow that down, so the tire can better follow the  terrain, keeping traction.

Edited by KRANNIE
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I have the 14, 20mm applied clamps, i run the forks flush with the clamp, and have .57kg springs in the forks. Rear i have the JGR lowering link and 6.7 spring. Bike handles a lot better now wants to steer with the rear of the bike. I have been using MX 52, but about to switch it out for a 32. 

 

I am 210 lbs and my sag is at 105 static around 27. Took me a while to get the bike feeling like i wanted but happy with it now. 

 

 

If you never changed your springs for your weight that is the 1st place i would start.. That alone made the bike feel alot better for me. Stock springs are too soft for bigger guys. front and rear springs are around $200-230 +fork oil. If you do it yourself.

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Yeah it's one of those things that might take a few hits and misses to find the right balance. It does have a feeling of too much wait on the front end which as you say may be causing the oversteer. I'll try a few of the things you guys have mentioned and see how i go.

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It depends why you are 'knifing'.

 

If you are getting to much weight transfer to the front when braking , you will break front wheel traction and over steer. 

 

Loss of front wheel traction to whatever degree is understeer.  Oversteer is when the rear wheel tracks outside the front in a turn.

 

And knifing is the opposite effect, really.  And pretty much the exact opposite of anything that YZF riders have complained about, ever.  It usually ends up loosing traction, but it starts as the tendency for the inside leading edge of the tire to dig at the ground and pull the steering in toward the apex.  That's a different thing with different causes than the simple lack of front end bite YZF's have always been knocked for.  

 

When the frame and steering geometry underwent its first major revision in 2010, they basically did a lot of the already popular cures for chronic understeer at the factory; forks a little more vertical, trail tweak to match.  So, when you raise the tubes on the EFI bikes, you're often times going beyond what was reasonably possible with the older bikes or any of the WR's in terms of head angle, and knifing is one of the things that becomes more likely when you adjust in that direction. 

 

As to the OP's question of spring rate, you can try that next if you think it needs it.  The bike is sprung relatively stiff, but they seem to work that way once you get them dialed, at least for MX purposes.  

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I have the 14, 20mm applied clamps, i run the forks flush with the clamp, and have .57kg springs in the forks. Rear i have the JGR lowering link and 6.7 spring. Bike handles a lot better now wants to steer with the rear of the bike. I have been using MX 52, but about to switch it out for a 32. 

 

I am 210 lbs and my sag is at 105 static around 27. Took me a while to get the bike feeling like i wanted but happy with it now. 

 

 

If you never changed your springs for your weight that is the 1st place i would start.. That alone made the bike feel alot better for me. Stock springs are too soft for bigger guys. front and rear springs are around $200-230 +fork oil. If you do it yourself.

.57 and 6.7?? Ive never even heard of springs that stiff. Most of what ive seen for 200 lb guys is pretty much what comes on the bike .50 and 5.8. Yamaha only offers one spring stiffer on the front (.51) and a couple of sizes stiffer on the rear, up to 6.0. You must have had some custom super stiff springs made

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.57 and 6.7?? Ive never even heard of springs that stiff. Most of what ive seen for 200 lb guys is pretty much what comes on the bike .50 and 5.8. Yamaha only offers one spring stiffer on the front (.51) and a couple of sizes stiffer on the rear, up to 6.0. You must have had some custom super stiff springs made

I was gonna say something but I'm glad you did instead...

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.57 and 6.7?? Ive never even heard of springs that stiff. Most of what ive seen for 200 lb guys is pretty much what comes on the bike .50 and 5.8. Yamaha only offers one spring stiffer on the front (.51) and a couple of sizes stiffer on the rear, up to 6.0. You must have had some custom super stiff springs made

 

You can buy any spring weight you need from Diverse Racing, right off the shelf.

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Yup diverse is where i got my stuff. I believe the front was 54 and the rear was 6.4. I just had it serviced and when they tested every thing it came out with the numbers mentioned before.

Forks also had 300cc of oil

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Well first you say .57 and 6.7 and now you "think" its .54 and 6.4. So you really dont know. Either way, thats too stiff for you at 210 lbs in my opinion, unless you just like a really stiff suspension.

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The numbers did seem out of range, but I was going by the described behavior rather than that.  It's also true that the rear linkage has been revised, and that can bear on the spring rate.  The good setups do tend to be higher rates.  A static sag check would tell you. 

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Well first you say .57 and 6.7 and now you "think" its .54 and 6.4. So you really dont know. Either way, thats too stiff for you at 210 lbs in my opinion, unless you just like a really stiff suspension.

Like i said i bought the stiffest or next to it from diverse that is what they recommended when i talked with them. I just had my stuff serviced and they put all the stuff on machines for what ever reason. This is the service record they sent back to me. It lists the spring rates on there.

Suspension feels great. Thats 210 with out gear.

image.jpeg

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I'm 200+ lbs and I run stock springs. 105 sag forks down 4-5mm. Biggest thing I've found is the mx52 likes 11-12 psi, makes a huge difference

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Went out today and put forks back flush went 2 clicks harder on compression and 2 clicks out on rebound and its a lot better. I think an MX 32 on the front might help it get a bit more bite but it's definitely improved. Thanks again.

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