For you guys that are wondering if the swingarm extends or compresses under acceleration you can try this experiment. Most of you will recognize this from experience without trying the experiment. Apply your front brakes and while keeping pressure on the front brake lever try to go forward. In other words, "power brake" your quad. This simulates the load the quad has under acceleration. You will clearly see the rear of the quad jack up from the swingarm extending. This phenomenon has been well known in motorcycle road racing for a long time. I read about this in the Keith Code book "A Twist of the Wrist" a while back. I immediately thought of the amp link when I read that, but I agree with the general concensus that the amp link isn't worth it. I've seen them fall apart too many times.

 

I have thought about getting a Z instead of the Raptor... until I read this tread

that swingarm scares me.... same as the LT250 with all the same problems, and more

plus weak axles..... and tires that have too much side bite...

it's like the entire back end of the Z is a piece of crap....

heck the front end is basically a 400EX.... the only good thing about the Z, is probably the motor and/or trans, but that's all too early to tell, really...

heck, with the Raptors tippynes, I think I'll probably wait to buy another quad until Honda comes out with a new one....
my 2000 400EX is just fine for now.... especially since I've only got $3,800 into it, and never spend a dime on it...

and my EX doesn't buck, tip, bend axles, blow tranny's, etc. etc..... and I've cased it, crashed it, flipped it, rolled it, sank it, you name it, it just keeps on ticking!

I'll admit it, the Raptor's power and bolt-on potential impresses me, but to be truely happy I'd have to change the swingarm, axle, A-arms, and tires... to lower, lengthen, and widen it.....

and the Z... doesn't impress me at all

 

Well the axles were fixed by Suzuki, the first bath was bad so thats not a worry, the Z spins it rear tires so much I am sure you dont have to worry aboutto much side bite all that much, and its not really anymore tippy than a 400EX, and it only bucks when you hit woops, not for normal riding, and it can't be any worse than the 250EX your wife has, my brothers has flipped because of that when I was riding it.

 

first i way 250 pounds and i beat the **** out of my z and i got no problems.and *** for bucking it dosent at all.i think it rider error not bike error.
i find the quad very easy and fun to ride.and i jump the crap out of it.i hit whoops pinned and it never bucks.i think if peopel new how to ride better they wouldn't notice all this dumd stuff.
if you ride like a wussy you notice stuff like that.and mine has been very reliable so far.and i have had no problems with the chain adjuster i think it very simple to adjust the chain!

 

Um to me normal ridding is in the woops. and ltz400man if you ride like wussy you dont feel any thing. and if more people ride like you our sport would be baned. Sounds to me like you ride ***** to the walls and have no idea of what your bikes is doing. I good ridder is fast and know whats his bike is doing and know how to make it faster (read FEEL). key word feel a fast ridder knows how his bike feels and should feel. Not to flame but you came out with that post in a bad way. there is no stock quad not even the cannondale moto that will handle great out of the box. with the moto you still need to tune it.
I have seen hints of the problem on my buddys z400 but I am not a pro level ridder so I can not say one way or another. And I did not spend alot of time on it. When the rear end commpresses and gets harder its called shock "ramp up". start off with lil stuff like sag, preload, chain slack and then make 1 ajustment at a time and keep notes trust me it helps. and watch your ridding style. viedo tape your self in the woops and then watch pros in the same size woops. I have learned to watch pros like a bird of prey staling its kill. They are fast for a reasion not by luck.

 

ltz400. the people are who are complaining about the swingarm are my no means beginners. WP races competitively in local so cal events. and i know surfer races a few high desert races each season

 

Being the nerdy MIT student that I am, I had to solve the problem of why the swingarm moves in the direction it does under acceleration.

I made a drawing of my potential answer also, to see it, go here: http://quadsport.mit.edu/swingarm.jpg

Here is my solution:

It has something to do with the tires and their rotation. When a tire is bearing down and rotating forward when under acceleration, it is effectively trying to run itself past the rest of the quad by rotating underneath it. That is what a wheelie is. Thats also why people fall backwards on wheelies. When the acceleration is not fast enough to pull a wheelie, the resulting torque from the tires instead act about the pivot point of the swingarm. Imagine your swingarm being free to rotate. It would effectively try to come underneath the quad until it was as forward as it could get.

Some might argue that doing a wheeling causes the front of the bike to go upwards and so the swingarm should compress. The difference in a wheelie is that the bike is rotating around the rear wheels and the only causing the suspension to compress in that case is the weight transfer to the rear. The fellow who gave the example of hitting the front brakes and accelerating is correct because this stops weight transfer and allows the suspension to move more normally.


If you have any questions, comments, criticism, etc of my answer, please let me know, i'd love to hear it.

 

Sorry, didn't put the link for the graphical solution in correctly:

here

http://quadsport.mit.edu/swingarm

 

Quadsportsman,
Thanks for making that clear. The drawing really simplified things. Speaking as someone who likes to wheelie and is also a thinke, your comparison to wheelies makes a lot of sense. I am still wondering how the angle of the swingarm contributes to the condition. I understand how the swingarm length affects leverage but haven't considered the angle before. What do you think?

 

YamhaBike,

the angle of the swing arm effects are explain like this...

"straighter" or "level" measured from pivot point to axle, would act as the rear tires are "pushing" directly into the pivot point on the swing arm. so little swingarm extention.


Now the more angled the or the pivot point being above the axel, when the rear tires are "pushing" forward, it is not dirrectly puching into the pivot point ,but under. So the swing arm starts to move forward "under the quad"

So simplfied, push the back of a straight line in the direction is faceing and it goes.

Now push on a the bottom edge of a triangle, and it would just fold under.


Disclaimer====== Im not saying the swing arm has to be straight, just trying to give a lamans terms example of how this works