headshake?



6 replies to this topic
  • YZThumpa

Posted December 18, 2000 - 02:02 PM

#1

As mentioned before, I am very inexperienced with only recent significant track time. My 2000 426 is totally stock. I didn't set the sag but I did turn out 3 clicks on the suspension. While the suspension initially felt harsh, it seems it has broken in a bit and I have gotten used to it also. The one problem I have is with the front end on hard landings. Just feels hard coming down, with some wobble involved, on the bigger jumps with flat landings. I'm assuming this is what they call headshake? Is this a suspension issue, a handlebar issue, or a work out and get bigger forearms issue? I thought I had heard people say aluminum bars help to eliminate vibration, etc. Would this help my problem also?

  • Hick

Posted December 18, 2000 - 02:26 PM

#2

Headshake refers to the bars shaking from left to right over rough terrain at speed.

IMO giving riding advice isn’t very useful over the net but on hard landings I like the rear suspension and my legs to absorb the bulk of the impact. So just before landing I’ll push the back down just a bit, then the impact of the front coming down can be handled in a pull then push fashion with your arms. Pull to slow down the falling front, push to absorb the impact.

I don’t want you to sprain your ankle(s) but I also use the ball of my foot on the pegs, then your calf muscles can provide more leverage to absorb the hit.

See, that didn’t make any sense at all, did it?

  • DaveJ

Posted December 18, 2000 - 04:42 PM

#3

YZ,

In my mind, it's a fork problem. Especially if the unit is bottoming.

I'm the king of bad landings in my neighborhood, so I know what both good and bad suspensions feel like in these cases.

By fork problem, I mean it's the design. It's not like you have had some sort of failure.

The main problem with these forks can't be fixed by turning the screws in or out.

And you may have already discovered that if you turn the screws out too far, the bike is much harder to ride. This is because any suspension has to have a level of firmness with it to maintain control of the wheel. If not, it just oscillates and this gets transferred to the rest of the bike and your arms.

Yamaha and KYB did a good job with these forks, but they are purely designed for the masses.
The main problems are this, 1. The cylinder heads fatigue (wear out) over time and rather quickly if the bike is abuse excessively. 2. The bottoming system arrives late and is insignificant, (less than one inch) and 3. The valve stack and flow profile has a very narrow window of performance.

So, how to fix. Most big name suspension shops can partially resolve the last issue. Other shops that are willing to plate the cylinder cap will help out with the first issue. Number 2 requires aftermarket heads or bottoming cones, which cost some money and are not an easy task for most people to install. This will also resolve the first issue. Whew!

I, and a few others, have poured some time and money into these forks and seen significant changes. Well worth it in my mind for the hours spent riding and the muscles saved in my arms.

Now it’s just a matter of how much this really bothers you.

And before anyone starts ripping on Yamaha, this stuff is similar for all bikes and all cars. Even Ferraris come the factory with plenty of room for improvement.

DaveJ

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  • Boit

Posted December 19, 2000 - 01:47 PM

#4

Hey Thumpa: I am soooo ready to get in some riding again. Haven't been on the back since our last race....the nasty weather an all. Hopefully, if the weather cooperates, we can get in a day of practice at Close Encounters. Game? :D


To add to a little of what Dave and Hick posted, there are a couple of dynamics going on that causes headshake. Suzuki RM's are rather notorious for this due to their relatively steep steering head angle(more toward vertical than the other makes). Suzuki seems to accept this annoying trait in order to get their machines to turn sharper. It's all a trade off. If the fork springs are too soft, the forks will sag too much and steepen the head angle a little....sometimes enough to exacerbate the head shake. You might consider an after market suspension company such as MX-Tech, RG3, etc. to have a good suspesnion setup. It's pretty amazing when you trust your suspension just how much faster and better you can ride. MX-Tech did mine and I am very pleased. Now, if I can just learn to be faster... :)

  • YZThumpa

Posted December 19, 2000 - 02:42 PM

#5

Hey, Boit. I haven't ridden since then either. I am going to try to get to the track either Saturday or the day after x-mas. Not sure yet- depends on the weather. I can put up with the cold, just not rain.

  • MikeOK

Posted December 19, 2000 - 03:54 PM

#6

Head shake is very unusual on a 426, in fact this is the first time I've heard of it since it's such a stable bike. Head shake usually means a steep head angle, meaning the forks are more straight up and down instead of more "chopper" like. And one thing that would steepen the head angle is the forks bottoming out. Some bikes were designed with a steeper head angle to make them better turners but the 426 isn't one of them. I would check to see if the forks were bottoming too much as above...

Mike

  • Boit

Posted December 20, 2000 - 03:48 PM

#7

Thumpa: I called James last night and Encounters will be open this weekend for practice, although I might have to put in some overtime at work this weekend since many guys are on vacation. I'll just have to play it by ear....plus the weather is iffy. Oh yeah, as it turns out, Encounters is racing on the 1st and 3rd Sundays of the month and this works out perfect for me. Since I work every other weekend, it takes about 5 or 6 months for my off weekends to move from the 1st and 3rd to the 2nd and 4th Sundays. Unless you've worked shift work, it probably makes no sense to you. Anyway, January starts a sequence of my being off on the race days as long as he sticks to the 1st and 3rd Sundays for racing. Hope to catch you there either Saturday or Sunday... :)





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