Rear suspension tidbit.
I read about a lot of big guys riding WR450s. I also read about people setting their race sag to numbers higher than 100mm, like 105mm, etc.
Here is a little secret. The WR450F steers terrible when the back end is low. They feel like ponderous pigs. The rider generally feels "behind" the bike in terms of control. When the suspension is set like this, you don't pick a line, you wish for a line and deal with whatever you get. Its awful.
The 2012+ WR450Fs only have 11.6 inches of rear travel. The recommended race sag on page 4-4 in the service manual is 90 to 100mm. That is the amount of sag that the Yamaha engineers had in mind when they set up the geometry of the bike. If you run more sag than this, expect it to be operating with geometry outside its design.
Furthermore, big, tall, lanky riders end up sitting further back on the bike. When they do that, they compress the rear suspension more and the bike turns like crap when you are seated. Especially when you are wearing a heavy pack, which moves the rider COG even further back. Sliding up to the tank helps, but the rider is constantly doing it and its a compensating move.
There are several possible solutions to the front/back balance problem. 1) Heavier rear spring. 2) Proper sag setup. 3) Raise the fork tubes in the triple clamps. 4) Move the bars ahead further. (Ever compare the arm reach of a 6'1" guy to a 5'10" guy ? That is how much further back the tall guy is on the bike, given the same arm position. Its like 2 inches and the tall guy is heavier too.)
My bike turns well with 92mm of sag, measured with me standing. I'm running a 6.0 spring even though race tech says I need a 5.8, max. I'm also running my bars further forward thanks to an extra set of holes in the YZ triple clamps. It all helps. My comparison bike is a 2010 YZ250F.
I've run less sag than that in testing. It turns better yet, but shock absorption is off because there is too much preload on the shock and not enough "free" travel.
My sag numbers also aren't right. When my race sag is in range, my static sag is like 12.5mm. I'm going to try a 6.4 spring. I expect it to improve the suspension as well as the handling. I'll report back when I do.
Edited by MidlifeCrisisGuy, September 08, 2014 - 11:41 AM.