YZ450F fork spring preload adjustment washer size

[Anssi]

Hi,

I was just wondering if anybody would know the internal and external diameters of the fork spring preload washers on the YZF and if there are any special material or other requirements.

The manual only tells the thickness and the Yamaha part number (for which our beloved importer is sure to give a huge price). I will ask them tomorrow, though.

 

[dbrace]

Any washer with the same outside dia. as the spring will be fine, as long as it fits over the damper rod. I suggest starting with a 2-3mm preload washer. On bumper rubber forks allways put the spacer under the spring, otherwise you will damage the bumper rubber and its components.

 

[Anssi]

Thanks, dude.

Anyhow, I already went and got a pair of them official Yamaha washers at a price of almost 5 euros/pc (about 5 bucks a pop).

 

[dbrace]

Cool, but why do you need more preload? What problems are you having? I will help if i can.

 

[Anssi]

I'm 200lbs. but I still got the stock spring to acceptable sag (20mm and 100 mm). I had to wind in three full turns (1080 degrees) of preload on the shock and started to feel a bit nose-heavy.

Put in 4,6 mm (full two washers) of preload in the front and I think I went too far (light nose). Compensated with losing 2 clicks of compression and adding 2 rebound. I will remove 1 pair of washers when I service my forks soon. Oil level is now tuned for light bottoming at the biggest hits.

 

[mop]

Anssi:
For your weight, I think that you must go up to the next rate front fork spring. I am not sure what the production standard spring is in Europe, but in USA, it is straight rate .46kg. I would recommend .47kg for you. There is a chance that European YZ's use progressive springs, but I am not sure. Straight rate and progressive original equipment KAYABA springs are available from Technical Touch in Belgium. They are the KAYABA importer for all of Europe.
For your weight, you should go up on both front and rear spring rates. Also, be sure to specify "kg/mm" for your spring rates, because in recent times, Yamaha and Kayaba have started using "nm" ratings:newton meters, and they are different.

 

[Jeff Howe]

Going from .46 to .47 is a waste of money. Minimal difference. Besides, at 200lb his springs are fine for him. In fact, he's doing a good job at getting it dialed in from what I can see.

 

[Anssi]

Shocknut, that's what I figured also. From what I can read in the manual, the shock spring is indeed progressive for Europe, but the fork springs are .46 straight-rate.

The .46 is also the highest rate Yamaha lists in the manual (although obviously aftermarket companies have higher rates). Since I got the sag fine, I'd rather loose a few more pounds and use the money for gas and tires.

I think I made a mistake having my 520SX revalved pretty hard and further made it worse by dialing in too much rebound damping. After that lead sled my YZ450 is a trip to Plush City (with none of the ill effects that usually come with it).

 

[mop]

excuse me? .46kg to .47kg is a "waste of money"?!?.........as in "no difference?"..........well, if you don't need a higher rate spring, it is a "waste of money", but if you do, then it certainly isn't. An increase of .01kg in each side fork is a noticeable difference, that most people can feel.