From Dirtwheels Jan 03, pg 52. "The swingarm angle is a tad too severe on this machine, causing excessive chain torque. That means under hard acceleration, the tension on the drive chain is so severe, it causes the rear suspension to expand and almost lock open. This makes for a rough ride over acceleration bumps and contributes to excessive wheel spin on smooth surfaces". What do you think?? I agree with them, and this is why:

A few weeks ago I did a post about being unable to get the rear suspension dialed in. In the big high speed desert whoops the back end bucks up, and to make it even worse, the front dives in. I THINK THE PROBLEM IS CAUSED BY THE CHAIN TENSION ON THE SWINGARM LOCKING UP THE SUSPENSION!! The way I handle whoops is as the front wheels just hit the first one I punch the throtle. This wheelies the front off the whoop, and the back suspension soaks up bump. Then the front tires land on the second whoop and we do the thing all over again. If you keep the power on, the front tires just skim the surface of the whoops, and the rear suspension eats up the bumps. This technique works great on every bike I have ever ridden. Even with stock suspension, the 400EX handles the whoops pretty well. Well, it doesn't work on the Z!!

What I think is happening, as I punch the throtle the rear suspension locks out and catapults the rear end into the air, which makes the front end pitch down. Common wisdom suggests that the back end bucks because the rebound damping is to light (the rear bounces back so quickly that it bucks the rear up into the air). Well, I kept turning the damper in, and the further I went the worse it got!! I am quite familiar with the chain torque lockout principle from the early days of mountain biking suspension, so this was always in the back of my mind as a possibility. Some early (Trek) mountain bikes use a motorcycle swingarm type rear suspension, and it was a miserable failure because chain tension would lock out the suspension during climbs (sadly after 15 years my cousin still rides one of these miserable machines!!). With the suspension locked out, the bike loses traction because a suspension that complies with the terrain has more traction than one that is rigid. Mountain bike designers quickly learned that you need a linkage suspension to eliminate this.

Anyway, what are your experiences??? I have to say that at trail bike speed, this isn't so noticeable (on the trails I ride, you don't get out of 3rd gear). It only became severely apparent when I hit the deserts this fall (after the hot weather cooled off). I bought this bike because its high rev engine makes for a good high speed desert ride, but I am afraid that I am going to be disappointed!!!! I don't think an aftermarket rear shock is going to fix this one???

Oh yeah. I have a 400EX and Z400 sitting side by side in the garage. They have the same tires and rims, and the suspension preload on both bikes is adjusted for 30% (3 inches) sag for a rider of my weight. YOU CAN CLEARLY SEE THAT THE ANGLE OF THE HONDA SWINGARM IS MUCH SHALLOWER THAN THE SUZUKI.

 

Do you have a pic of this. I personally hate the Z swingarm. I came back from riding today and noticed that one of the carrier pinch bolts was missing. I just replaced one of the pulling bolts for adjusting the chain after it broke and I doubled up on the wrench for additional torque. I know it was tight. I am going to save up and buy a new one soon. They copied Honda so much that they sould have taken the swingarm to the next level and had a better adjusting system.

 

The first high performance quad I owned was an '87 Quadracer 250 ann at first I had the same problem with that quad. In the end the problem was with me or, more accurately, with the adjustments I was making to the rear shock. You should be running as little rebound damping as possible, allowing the rear suspension to extend as fast as you are comfortable with (to suit your riding style). Increasing the rebound damping (making the rear suspension extend slower) more than is absolutely necessary only causes the rear to "pack down" after hitting several bumps in a row at high speed. As I said, I thought the rear of my quad was kicking up too fast and When i did as you did the problem got worse. It was only after someone told me how low the rear of my quad was riding while running through a long whoop section that I figured it out. Also I doubt the Z400 suffers from the chain torque phenomenon any more than all quads do, but try lowering the ride hight by backing off the preload some. I would get the rebound dialed in first, though. Also you can do an internet search on suspension tuning and there are several sites that can guide you through the entire process. I would also make sure that the compression adjustment is in the ballpark and not too stiff for your weight or the rear will kick for sure. Check your current settings and write them down, so you can go back if you dont like the results and only adjust one item at a time. Hope this helps

 

i have a kfx400 and when i attempt whoops i can ride them easily. i dont know if my back end is lifting up or not, but it is easier on this than it was on my lakota.

 

I'm having the same problem with the chain adjustment bolts and the 4 bolts that hold the swing arm from moving, I also replaced one bolt and now have to do it again pluse the upper bolt that holds all the chain tight. I don't what to do ?

 

Cannibal-I have had years of experience adjusting (aftermarket) suspensions, and I am absolutely sure this has nothing to do with the shock adjustments!! Stock preload sags 5" at my weight (190 lbs), which reduces usable suspension travel to only 4" (which is just plain ridiculous)!! Furthermore, even at 5" of sag the condition isn't any bit better. Stock preload on the Honda is also 5" , and when I crank it up to 3" it doesn't have this problem. (I think manufacturers purposely set the stock preload real mushy, so that while you are jumping up and down on the bike in the showroom, you imagine that it has REAL PLUSH suspension. Most riders never touch their shock, and if you notice most are riding around with something like 5" of sag, which is to much.)

The rear shock mount is part of the engine case. I haven't taken a close look at the dirt bike, but perhaps what happened is that Suzuki didn't want to make separate engine case molds for the quad, so they just compromised and used the dirt bike height (which is to high for the quad). Like I said, at trail speed it is not so noticeable. But when you are bashing huge desert whoops at 60 mph with 5 Banshees on your tail, this swingarm falls flat on its face!! Maybe we can count on the aftermarket for a fix???

I have also experienced a lot of WHEEL SPIN (just wasted power!!). At first I attributed it to the great revs that this engine builds. But under closer analysis, I think it can also be blamed on the swingarm geometry.

 

YZGuy, I hope I didn't offend you. It's obvious (now) that you have a good understanding about suspension tuning. That wasn't so clear from your first post, however, I guess 'cause I didn't have all the info. Anyway, consider this: the torque from the chain pulls the swingarm up, not down, causing the suspension to compress, not raise. This causes the suspension to move to a stiffer portion in the travel because of the leverage curve designed into the linkage. In my past (and present) experience reducing the rebound damping to a point will reduce the tendancy for the rear to kick while going through deep whoops. Doing this allows the rear suspension to unload and move back into the softer first few inches of travel. Anyway I don't own a Z400 and I only rode one briefly, so I'll just say that from what I remember the Quad rode smoother than mine, but I didnt have a chance to really push it. I was really considering the Z400 before buying the Cannibal, but I got a deal I couldn't pass up. Good luck solving that one, and let us know how it turns out.

 

TCS

 

I'll agree w/ WP that suzi could have come up with a better design, but honda's design is patented, so they couldn't go there. (darn it!) hehehe

 

i have a swing arm comming for my Z that converts everything from the pivot back to 250R geometry. it will use my 250R millenium bearing carrier, 250R dominator 2 axle, anit fade 250r lock nut, sprocket, and brake disk. with the rear shock getting rebuilt by TCS we'll see how she performs after that