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skthom

rear suspension?

18 posts in this topic

Hi - I need a little help here. I've got about 10 hrs on my '01 426 (first bike in 20 years) and am starting to get a little faster. Along with that I'm noticing that the rear end "kicks out" a fair amount when going over jumps or bumps w/ a lip. It's doesn't seem to favor one side or another.

Also had some problem with sandy whoops where the rear starting jumping from side to side at speed.

I am two clicks softer than stock on the front, stock in rear. I was thinking of starting w/adjusting the rebound damping...

I am 185 lbs w/o gear and would consider myself a novice/intermediate rider.

:)

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Man another Houston rider (I live in Friendswood), there are a bunch of Houston area riders on this b-board!!! Welcome to Thumpertalk! This place has tons of useful info and is very addicting LOL :) ! Later,

Garrett

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Here is a printable tuning guide.

This guide was downloaded from the MX-TECH.COM website.

It sounds like your shock is "packing", which means that your shock is rebounding too slowly. You are hitting a bump, the shock compresses, ideally you want the shock to fully extend before the next bump to be able to soak up the hit. Your shock is rebounding too slowly, in other words your shock is not fully extended in between bumps, you are hitting the bumps with the shock already partially compressed, and it doesnt have the ability to fully soak up the bumps which causes the back end to "kick out"

I would reccommmend that you "soften" up (make faster)the rebound by turning your rebound adjuster out 2 clicks at a time untill the bike quits kicking.

GETTING STARTED, SHOCK:

SETTING THE REBOUND:

1.) Find a relatively fast straight with braking bumps leading into the entrance of a corner. Reduce (Turn clicker out) the rebound damping until the rear end begins to hop or feel loose. Finally, increase (Turn clicker in) the rebound damping until the sensation goes away.

2.) Find a jump that tends to launch the motorcycle out. The rear end should absorb and then smoothly lift the motorcycle into the air. If the rear end bounces up, add rebound. (Turn clicker in)

3.) Find some large whoops. The motorcycle should track straight through the whoops with the rear wheel extending to the ground before the next impact. If it does not perform as described as above, it is packing and the rebound damping should be reduced! (Turn clicker out) (Please note the guide for sand set-up, as these rules don't apply for sand.)

SETTING THE COMPRESSION:

1.) Find a corner with acceleration bumps on the exit. The rear of the motorcycle should follow the ground. If the rear end "breaks up", soften the compression. (Turn clicker out) (If this fails soften the rebound two clicks.) (Turn clicker out)

2.) Find some rough sections, a large jump and a couple of "G-Outs". The shock should bottom on the roughest section but it should not be a slamming sensation. Add compression to fight bottoming. (Turn clicker in.) But avoid going to far as small bump ride will be sacrificed in the trade. Remember the adjusters have a primary effect on the low speed, so even a large change in setting may only affect bottoming resistance slightly. Remember bottoming your suspension is not necessarily a bad thing. You should strive to bottom off the biggest bottoming load obstacle on the track. If you don't you're not getting maximum plushness from your suspension.

.

GETTING STARTED, FORKS:

SETTING THE COMPRESSION:

1.) The forks should react to all track variations. If the forks seem harsh on small bumps or holes, soften the compression. (Turn clicker out) If they aren't, stiffen (Turn clicker in.) until they do feel harsh and then turn back a click or two.

2.) Now find the rough part of the track again. The forks should bottom over the worst obstacle. If harsh bottoming occurs, add oil in 5 mm increments.

SETTING THE REBOUND:

The rebound damping is responsible for the stability and the cornering characteristics of the motorcycle.

1) Find a short sweeper. When the forks compress for the turn, the speed at which the forks return is the energy that pushes your front wheel into the ground. If the forks rebound too quickly, the energy will be used up and the bike will drift wide, or wash. If the rebound is too slow, the bike will tuck under and turn too soon to the inside. Find the appropriate balance for each track.

2). With the bike turning well, the wheel should return to the ground quickly yet not deflect off berms or bounce off jumps.

Going to different tracks:

For hardpack to intermediate:

Set the compression softer, (Turn clicker out) front and rear to help get maximum wheel contact and plushness.

Sand tracks:

(Non-square edged bumps); More low speed compression and rebound are necessary. Start by adding 1-2 clicks (Turn clicker in.) of rebound and as the track gets rough, add compression 1-4 clicks. (Turn clicker in.) (Supplementary sand set-up techniques). Harshness is a result of packing in forks. Remember to add compression (Turn clicker in) to help keep the front end from packing. The rear suspension will exhibit packing by swapping. To eliminate swapping begin adding compression (Turn clicker in) until the bike tracks straight and then add rebound (Turn clicker in) to keep the rear following the terrain of each whoop. Don't be concerned if your clickers are nearly maxed out in sand conditions. Unless of course you had your bike revalved for sand.

Supercross:

(G-load, curb hits); G-loads produce slow piston speeds. This means that less dampening is produced by the shock and forks in a situation that causes more of a bottoming load. To set your bike up for Supercross adjust the compression stiffer (Turn clicker in) on the suspension (2-6), clicks and in some circumstances raise oil level and/or change to stiffer springs.

Unpleasantries?

Headshake:

Adjust the forks lower in the triple clamps.

Excessive rear end kick:

Check for packing, which is identified by kick to side in hard to loam conditions. If you observe packing, soften rebound. (Turn clicker out.) This cannot be avoided if you brake improperly and lock the rear wheel up and/or pull in the clutch, on the entrance to corners.

Keep a record of the different settings if you race different tracks. That way you can start at a point that worked well the previous times.

Good Luck, John

[ October 29, 2001: Message edited by: John Curea ]

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<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:<HR>Originally posted by motoman393:

Man another Houston rider (I live in Friendswood), there are a bunch of Houston area riders on this b-board!!! Welcome to Thumpertalk! This place has tons of useful info and is very addicting LOL :) ! Later,

Garrett

Thanks for the welcome. Actually I'm in The Woodlands. And yes, the site is both addicting and useful LOL! Without it I would not have learned so much about the bike in just the few short weeks I've owned it.

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Thanks for the tuning guide. I'd seen it before but couldn't find it when I searched. It didn't really make sense to me earlier as I hadn't had enough time on the bike! It definitely sounds like the shock *is* packing. I'll go through the tuning efforts my next time out. It sure is hard to actually stop riding and tune things though. These bikes are too much fun!

[ October 27, 2001: Message edited by: skthom ]

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No, packing happens when you hit a few bumps in succession. If it is kicking on the take-off of a jump, it is probably the rebound set too lightly.

First thing you need to do is set the rear sag and *then* start playing with the clickers.

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<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:<HR>Originally posted by MX Tuner:

No, packing happens when you hit a few bumps in succession. If it is kicking on the take-off of a jump, it is probably the rebound set too lightly.

First thing you need to do is set the rear sag and *then* start playing with the clickers.

Sag has been set already.

I'll play with the clickers on the rebound damping next time out.

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Tuner

He said his rear was " kicking out " over jumps "with a lip". If the bike was "kicking up" over a jump without a lip, then I would agree with you.

Also he is having a problem with the bike kicking out in sandy whoops, which is the same thing as you describe packing as "hitting a few bumps in succession".

A bike that is kicking sideways is usually packing.........

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Kicking is (depending on speed and obstacle size and shape) primarily excessive high speed compression dampening.

You can try backing the high speed compression adjuster on the rear shock out(17mm red nut on resevoir, less high speed- turn counter clockwise).

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OH yeah, usually the high speed shim stack in the rear shock would have to be changed, when the shock has dramatic symptoms such as yours.

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Paul

The riding conditions that he is describing,jump take offs and sandy whoops are strictly low speed situations.

High speed hits are more like sharp edge hits,rocks, roots, potholes. These type of sharp abrupt obstacles will cause "high speed" movement of the shock and fork.

Jump take offs and sandy whoops will use much more travel, but the shaft speed will be much slower.

Sandy whoops need more low speed compression damping than a typical MX enviroment.

He needs to "lighten up"(counter clockwise) the rebound adjustment to stop the bike from kicking out, if you lighten up too much on the rebound the rear of the bike will have a tendency to "kick up" giving you that "going over the bars feeling".

The rider should back off the rebound until the kicking out sensation is stopped and the bike just starts to kick up, then go a couple of clicks clockwise. This should give a balanced ride.

No need to mess with the high speed compression stack........

Take Care, John

[ October 29, 2001: Message edited by: John Curea ]

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SKTHOM

Kicking is harsh (on your butt and lower back).

To little rebound is like butterflies in your stomach.

Since kicking refers to an impact induced movement or in this case a lack of shock movement.

Because the rear shock did not move enough and the force directed at the shock from the wheel is transmitted to the chassis and felt as a "KICK".

So to reduce the kick we must change the shock to allow it to move further more easily.

You are not going to be able to "wax" the shock to fix this one, you are going to have to make a serious change. PT

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This is a great topic, another good reason why TT needs a suspension forum !!

Suspension is a specialty all by ITSELF!

We'll see what SKTHOM says after he comes back from riding and making some adjustments....

Take Care, John

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Thanks to everyone for the advice. As John mentioned, I will go riding this weekend and post the results of my twiddling!

Steve T

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here are the yamaha race team settings for there stock bikes...forks.. oil level 90-100mm.. rebound 10-12 clicks out..compression 10 clicks out.......

shock rebound 10 clicks out.... low speed compression 8 clicks out.. high speed compression 1 1/4 turns out.. sag --95-100mm

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Sorry I've haven't replied to the list until now. I've been having WAY too much fun riding the bike!

I tried adjusting out the rebound damping two clicks at a time until the rear felt like it was "kicking up" over jumps rather than out, then I went back in (more damping) one click. That was it! Problem solved.

Thanks for all the advice.

Steve T

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HOW BOUT' TRYING THE RACE-TECH FIX!

i ABSOLUTELY LOVE MINE NOW!

GOLD VALVES

ULTRA LITE OIL

UP THE NITRO :)

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