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2016 450FX - same frame/steering geometry as 450F?

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I'm trying to balance the chassis of my '16 450FX and get the cornering to be the same as my prior bike ('14 YZ450F).  In stock form, that bike cornered absolutely mint.

According to the magazines/reviews, the changes to the chassis of the FX from the motocrosser are:

- Longer rear shock

- Different sprocket combo (and axle setting)

- Different springrates and valving

- Different tire sizes (90 width front instead of 80)

 

Triple clamp offset is supposed to be the same.  In an effort to replicate the steering of the 2014, I've got the shock length corrected, the tire sizes corrected, and the sprocket combo corrected to all be the same as the 2014.  

It's 90% of the way there, and the suspension action is actually REALLY good with the stock valving but there are two issues I'm still chasing.  One is a "heavy-ness" to the steering which I can't pinpoint the cause of.  The other is either a tuck or a push to the front end on loose corners.  Again, I can't tell if it's an understeer or oversteer.  The front end wants to flop over and twist the bars if I initiate a lean just the right way (or wrong way) or do any front or rear braking in loose terrain.  The front wheel will "shovel" to the outside of the corner at the steering lock and dump the bike.  It's pretty immediate and not something I can recover with body english, throttle, or brake.  I haven't been able to dial it out with compression clickers or sag.

I know the front springrate is just a little bit too soft for me.  The rear is pretty bang-on.  I can't find the right length fork springs for it at the moment, since they're shorter than the 450F springs, so I'll get that changed in a couple weeks.

Failing that, has anyone verified if there are any frame differences between the FX and the motocrossers?  Slight changes to steering angles?  Fork length?  Major difference in frame flex from the mounts?

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From what I know the frames are the same, but the motor mounts and head stay are different thicknesses (thinner on the FX) to allow for slightly more frame flex.

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Get the aftermarket link for the linkage, then you can set the sag and fork height with a more even weight distribution

My FX has the same issue; there is a vaugeness off of center steer that causes me to over correct...unless I set the sag really small, but then the forks blow through the stroke too quickly, unless I go in on compression, and then the ride is harsh.

I've done some research, and for me it seems the link will lower the rear end a bit, moving the weight back when braking and turning

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I had a friend measure a few things on his 2014 YZ450F for me to compare.  If his measurements are correct, the FX has a 2 degree steeper steering angle than the 450F.

Fork length from top cap to axle:  37.5" both bikes

Front axle center to swingarm center:  38.25 on 2014 YZF, 37.0 on 2016 FX.     Change of 1.25".

Wheelbase: 58.75" on 2014 YZF, 57.5" on 2016 FX.  Change of 1.25"

We'll get accurate headtube angle/fork angle measurements later on.  His bum foot right now prevents him from doing so, and the anglefinder app on my phone doesn't do so great with the case on it.

Forks flush on both bikes.  Same sprocket combo on both bikes and same axle setting.

That's a HELL of a lot of steering angle change.  It's almost enough for me to consider finding a 2014/2015 frame.  Almost....it's also enough for me to second guess his measurements too.

Why the F can't Yamaha list things like this as a change in their releases and reviews?

Edited by GHILL28

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A 2014/15 YZ is a different frame than a '16/17 FX

While I commend you effort, you aren't really measuring things that will define a specific difference.

Measuring from the front axle to the swingarm pivot tells you nothing.....other than the swingarm pivot has moved in relationship to the front axle.....and so could everything else.....and that has nothing to do with steering stem angle, and still does not take into account trail or offset....

 

You can't swap frames, so the only option you have is less offset triples, and someone setting up your suspension properly so it stays higher in the stroke.

 

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Triples and lugs are the same. So if the center to center is known, and the fork length is known, and the headtube location is assumed to be in the same spot, then you have the steering angle.

I'm thinking that he's reading his tape measure wrong. An inch of front-center change, or two degrees of steering angle would be massive. The handling is a little bit off, but not THAT far off.

Sent from my SM-G900V using ThumperTalk mobile app

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