ZX6R rear shock *sorta* howto

[TheDuck]

This weekend I have a cold, its raining and I don't have to work for a change, so I had to do something to keep myself busy! As a big plus, its actually WARM enough (surprising since this is supposed to be Florida!) to work on this thing, oh, and I was told that this couldn't be done... so here it is:

Tired of the rear shock being too bouncy for all of the 6'3" 250lbs of meat that I am, (much heavier with gear and other travel-related equipment) plus and not having adjustable bump or rebound left me a little frustrated.

I had the preload adjusted to the max and the thing still sagged a little too much. So I've known I wanted to do something to upgrade the rear, and the SV650 shock that some people have recommended really didn't leave me happy. I have an SV650 and its shock isn't adjustable for anything other than preload either.

I know that the 250 isn't meant to be a performance bike, but with a little work, who says it can't be?

I put the triple stand on the front and supported the underside of the bike with a floor jack and some wood under the kickstand to ensure that the bike's weight was NOT on the back wheel. Then popped off the caps on the side of the frame and removed the top shock bolt, then removed the bottom and pulled the shock downwards and out. Then I dug in the parts bins for a suitable replacement.

From left to right: 08-10 250R, 04-05 10R, 06-07 ZX6R



The 10R shock and the ZX6 shock measure the same length, but they are both about 1" longer than the 250R shock. This will raise the rear some 2 inches or so. We'll see how that turns out, and if I don't like it I'll get a set of lowering links.

The other dimensions such as the inside width of the forked bottom and the eyehole width at the top are identical on all, but the 250R shock has bigger bolt holes on top and bottom. This should be easy to ream out to the right size.

ZX6R on left, 250R on right:


The 10R shock also quite obviously has a different reservior from the ZX6R and the 250R doesn't have one at all! There will be some work to make this fit in on my 250.

After poking around I decided the 10R shock will fit better on another one of my projects so I decided to keep that one for later.

The ZX6R shock is much larger in every way, the spring is bigger, its about 1" longer and required stuff be taken off to make sure I can get it situated into its new home.

[TheDuck]

I would also like to add that anyone that is interested in this mod may not be able to do it with a stock airbox (though I think you can heatgun it and try to warp the bottom.) Or you can spend some money and get an Ohlins with a remote reservoir, or some other 2nd gen 250 aftermarket shock (I don't know of any at this time.)

Begin teardown, for anyone that has deleted the airbox knows just how much work it is to get into the middle of this bike. You have to tear off the complete undertail, so that requires removing anything attached to it, and anything attached to the things attached to the things attached to the things attached to the things attached to the things attached to the things attached to the things attached to the things attached to the things attached to the things attached to the things attached to the undertail.

Needless to say you wind up with a big pile of stuff. Pile your parts someplace safe where they won't get stepped on or disturbed:



And here's the bike sans rear end:





And a closeup of the top shock mount on the frame (note the pod filters):



I went to drop the ZX6R shock into place, but it wouldn't fit between the suspension links underneath, they weren't spread wide enough apart, so I took them off then mounted the shock, then attempted to measure how much clearance I needed.

I found that the links are offset a bit to the right, so the left side needed more washers to clear the new shock. This also required some longer bolts, so a trip to the hardware store was required, upon return and assembly, we got this:

[TheDuck]

So now comes the top shock mount... the top hole had been reamed out to fit the 250R shock bolt, but it just would not line up with the hole. It was really close but the shape of the shock interferred slightly with the frame. I shoved a screwdriver in there just to hold it in place, thats as close as it got. You can also see that the undertail was trimmed a little bit for clearancing of the reservoir.



There was two options, grind the frame to fit, or grind the shock, or a little of both. I believe when you're trying to add something custom that doesn't belong there, and then you have a problem so you need to revert back to stock, its better to modify your add-on rather than the bring the moutain to Mohammed.

I fired up the angle grinder and zinged off a little metal from the top of the shock... I didn't need to take off much, and its aluminum so it only took a few careful minutes to cut it right.

[TheDuck]

So the shock is now officially mounted:

[TheDuck]

I put the wheel on and pushed down on the tail and was quite surprised how much stiffer it was than the other 250 in my garage. This one actually pushes back when you push down on it, it doesn't just give out like an 80 year old without his viagra.

I threw the seat on and bounced my ass on it (keep the jokes to yourself) a little to be sure that nothing was binding or loose. My very first impression on it again was that it felt so much tigher than before, and yes indeed it was about 2" taller with a much more aggressive stance. This will affect my rake and trail on the front end.

I continued trimming the undertail until I had a shape that I was happy with an 1/8" gap around the reservior that cleared the shock in its full motion. After cutting it I thought to myself that I should have just heated it up with a heat gun and pressed the shock into it to make a nice and NEAT impression in the undertail... ahh well, next time. I'm going to put a plastic flap with holes that line up with the battery box bottom holes to cover that area and keep road grime off my air filters.

[TheDuck]

And lastly here it is on the bike (ignore the worn tire, its out of life so I have been smokin' it getting my money's worth of fun times out of it! It goes in Tuesday for a new one!):



Without making any adjustments to the shock, I took it for a ride around the block, and the first thing I noticed was that when I got on the throttle the rear end doesn't sag like it used to. Its firm, I can feel the rear end keeping its place, also when getting on the brakes the front doesn't dive as much, probably because the rear shock doesn't rebound as quickly as the stock shock thus pushing the tail up.

It also turned a lot easier with the tail higher, a lot easier than what I remembered before. I wanted to push it harder but I didn't press my luck on the wet roads though.

Here is a photo of the blue modified bike next to the red stock bike. Please excuse the photo darkness the rain wasn't helping, and the flash wasn't cutting it.



The rear is just under 2" taller when standing upright. The kickstand seems a little short, but works ok. I will ride it like this for a little bit and possibly invest in links later unless I can find some in the garage someplace.

[tapdiggy]

Were there any other reasons for choosing the 6R shock other than the easier fitment?

[TheDuck]

Originally Posted by tapdiggy

have you thought on working with the front forks to balance things back toward neutral, as far as weight distribution?

Mmmm yep, next writeup will be 636 fork upgrade.... shhh don't tell anyone.

[tapdiggy]

Originally Posted by TheDuck

Mmmm yep, next writeup will be 636 fork upgrade.... shhh don't tell anyone.

yes i will keep this public thread totally quiet

[Betlog]

that's awesome. post side-shot pics of the whole bike.

[TheDuck]

Originally Posted by n00br1d3r

that's awesome. post side-shot pics of the whole bike.

As soon as I have some daylight you'll have your wish!

[MKlein3004]

this is awesome to know man. Me being a little bit larger than others also, makes me want to look into this mod. Thought i am currently on a workout and diet regime that will hopefully net some weight loss, this is an awesome idea and i will keep up with this as it goes along. Thank you for taking the plunge.

[Rayme]

I love all the stuff you do to your bikes. Awesome.

[2WheelGuy]

That is cool that you've found superior shocks that can be swapped but I would worry about the extra length. On my race bikes I run the shocks longer but the max I go it about 1/3 the length you are adding. I'd be scared to ride a bike at speed with the back raised that much.

If I were to do your swap I would make a pair of longer dogbones to adjust for the longer shock.

[TheDuck]

Originally Posted by 2WheelGuy

That is cool that you've found superior shocks that can be swapped but I would worry about the extra length. On my race bikes I run the shocks longer but the max I go it about 1/3 the length you are adding. I'd be scared to ride a bike at speed with the back raised that much.

If I were to do your swap I would make a pair of longer dogbones to adjust for the longer shock.

Did you read my last sentence? Yes I will probably put some lowering links on there. Gonna try it as/is for now, until I finish looking through my garage for a set of links that will work, if I can't find any I will purchase a set.

[HKr1]

Nice!

And I really like threads with lots of pictures

[TheDuck]

Originally Posted by n00br1d3r

that's awesome. post side-shot pics of the whole bike.

Originally Posted by HKr1

Nice!

And I really like threads with lots of pictures

More pics, here ya go!

Before:




After:

[divingtigger]

Can't you compress the new springs to remove them and cut a coil off?? or even swap the springs from the 250 one to the new one to retain the height but have a better shock?? Did that on my wifes 66 mustang to drop the front end a couple inches. I have also done this on other vehicles.

[TheDuck]

Originally Posted by divingtigger

Can't you compress the new springs to remove them and cut a coil off?? or even swap the springs from the 250 one to the new one to retain the height but have a better shock?? Did that on my wifes 66 mustang to drop the front end a couple inches. I have also done this on other vehicles.

Nope, the length is determined by the stops inside of the shock. Replacing the spring, or cutting it will only mess up your preload. You'll have to crank the preload waaaaaaaay tight just to bring it back to where it should be, and thats just counter-productive as there would be absolutely no benefit.

[Plasmatoast]

alright enough of the Shock, Tells us about that color matched Area-P

[TheDuck]

Originally Posted by Plasmatoast

alright enough of the Shock, Tells us about that color matched Area-P

Sure! June 20th, 2009:

Area-P Exhaust.... COLOR MATCHED!

[Plasmatoast]

well i feel foolish, not sure how I missed that one. Looks really nice.


so back to the shock hows adjusting the preload, any issues getting access to the collar ?

[TheDuck]

Originally Posted by Plasmatoast

well i feel foolish, not sure how I missed that one. Looks really nice.

Heheheheheh!

Originally Posted by Plasmatoast

so back to the shock hows adjusting the preload, any issues getting access to the collar ?

NONE! I can get to all adjustment screws without having to bend anything, remove anything, tuck my male parts, or stand on my head! It was almost like that shock was meant to be in there! Everything easily accessible from the left side!

But, I haven't felt well enough yet to make any adjustments... still getting over being sick... once I have recovered and that tire is replaced I'll keep you posted.

[TheDuck]

I rode to work today on it, and OMG that thing wheelies easy! The back end doesn't MOOSH down anymore. I'll have to experiment further on a warmer day when the tires stick better.

Also the rear end is kinda high, I shaved my seat down to make it flat over a year ago, and it feels like I'm sliding down the seat and my nuts are being smashed into the tank again. Blah!

I can't find any good links in the garage, so I'll steal some off a parked ZX10r.

[Betlog]

Originally Posted by TheDuck

More pics, here ya go!

Before:




After:

It actually looks good with the back high up like that. Get some clip-ons to lower the handlebars and some rearsets and you're in supersport riding position, lol.

How does it ride on corners?

[Betlog]

Originally Posted by 2WheelGuy

That is cool that you've found superior shocks that can be swapped but I would worry about the extra length. On my race bikes I run the shocks longer but the max I go it about 1/3 the length you are adding. I'd be scared to ride a bike at speed with the back raised that much.

If I were to do your swap I would make a pair of longer dogbones to adjust for the longer shock.

Noob question here, how will the raised rear affect handling? Supersport bikes have rears that are about that high.

[2WheelGuy]

Originally Posted by n00br1d3r

Noob question here, how will the raised rear affect handling? Supersport bikes have rears that are about that high.

I'm not a suspension expert, this is just what I've picked up after years of working on and around race bikes.

I think you are confusing the rear subframe height with chassis geometry. Race bikes have high tails to keep the riders weight forward to keep the front end down.

Changing the length of the shock, (or dogbones) changes the height of the rear of the motorcycle. A longer shock raises the bike and increases the swingarm angle. Increasing the swingarm angle decreases the amount of squat the bike gets mid-corner making it easier to turn. The downside is that the rear wheel spins up more easily leading to highsides (not really an issue on 250 Ninjas). Raising the rear also buys you more ground clearance (a good thing on a 250). Raising the rear also has an effect up front by shifting more weight to the front tire and decreasing trail. Shifting weight to the front tire is a matter of personal preference. I like riding on the front but if you overload the front tire you will lose traction and low side. Decreasing trail will make the bike steer quicker but will also make it less stable and prone to head shake.

Like most things in life suspension geometry changes have trade-offs. From the factory bikes come with a safe neutral setup. Modifying the geometry can make the bike easier to turn but will make it less stable. Go too far and it will be unsafe to ride.

[TheDuck]

Well I'm a little short-legged for someone of my size and when I tried to reach the ground a couple times while shimmying around in a parking lot I almost dumped it expecting the ground to be there when it wasn't!

I lowered it back down with some nice adjustable links:

[Betlog]

Originally Posted by 2WheelGuy

I'm not a suspension expert, this is just what I've picked up after years of working on and around race bikes.

I think you are confusing the rear subframe height with chassis geometry. Race bikes have high tails to keep the riders weight forward to keep the front end down.

Changing the length of the shock, (or dogbones) changes the height of the rear of the motorcycle. A longer shock raises the bike and increases the swingarm angle. Increasing the swingarm angle decreases the amount of squat the bike gets mid-corner making it easier to turn. The downside is that the rear wheel spins up more easily leading to highsides (not really an issue on 250 Ninjas). Raising the rear also buys you more ground clearance (a good thing on a 250). Raising the rear also has an effect up front by shifting more weight to the front tire and decreasing trail. Shifting weight to the front tire is a matter of personal preference. I like riding on the front but if you overload the front tire you will lose traction and low side. Decreasing trail will make the bike steer quicker but will also make it less stable and prone to head shake.

Like most things in life suspension geometry changes have trade-offs. From the factory bikes come with a safe neutral setup. Modifying the geometry can make the bike easier to turn but will make it less stable. Go too far and it will be unsafe to ride.

Thanks for the explanation!

[Roostre]

Duck,

A couple question. Great work BTW!!

How much do you weigh geared up and ready to ride?


How is the handling now vs. the stock shock?



It would seem that the 2" might be easily negated by a 200+ lb rider, so that it really is only 1/2"- 1" higher than stock with a 135lb rider...hmmm.

[TheDuck]

Originally Posted by Roostre

Duck,

A couple question. Great work BTW!!

How much do you weigh geared up and ready to ride?

About 280-285lbs with all gear and my bag of tools that I take to work on commute with a full belly of breakfast before pooping (I drop one about noon.) I come in more like 260-265 with just my gear on.

Originally Posted by Roostre

How is the handling now vs. the stock shock?

The rear end doesn't bounce anymore, and the front actually shimmies less when my hands are off the bars... go figure.

Originally Posted by Roostre

It would seem that the 2" might be easily negated by a 200+ lb rider, so that it really is only 1/2"- 1" higher than stock with a 135lb rider...hmmm.

The extra 2" height was too much for me, I am big, but short-legged, and it was throwing me off as I was having trouble reaching the ground.

When I expected the ground to be there like when backing out of a parking spot, I found my foot flapping in the air and not finding the ground as my weight was shifted to that side, my heart would end up in my throat because I thought I was about to take a spill. Within a split second I'd find the ground though, but it'll make your butt pucker, lol.

For that reason I got some adjustable links and dropped the rear back to where it should be.

Right now the bike is grounded, the cords have started to show through the tires and I have been waiting on some new tires to come in...... still. I keep getting backordered. Everytime I am told they are coming in they don't arrive, so the wheels have been off the bike for the past week.



I'm not complaining though because meanwhile I'm tooling around on my SV650. That thing needs a suspension swap next... it will get its own writeup on the svrider forum, I'm sure.

[Snake]

Originally Posted by TheDuck

About 280-285lbs with all gear and my bag of tools that I take to work on commute with a full belly of breakfast before pooping (I drop one about noon.) I come in more like 260-265 with just my gear on.

Very funny but probably a little Too Much Information (TMI).

[TheDuck]

Originally Posted by Snake

Very funny but probably a little Too Much Information (TMI).

Well, he wanted some weightage, and I was trying to be as accurate as possible.

At about noon though, the sound of that thing hititng the water is like dropping a cantaloupe from chest height into the bowl.

[BuckyNaked]

Any advice for heating up the undertail and molding a place for the shock and reservoir? Hopefully I'll be doing this swap this weekend...

[sowega]

I just ebayed a Zx6R shock to do this to my racebike. Any developments since the last post?

[TheDuck]

Originally Posted by sowega

I just ebayed a Zx6R shock to do this to my racebike. Any developments since the last post?

Yep, I sold the old one for $50 and its been working great!

Oh and I did the suspension work on the SV650 that I talked about.

Link to original page on YouTube.

Link to original page on YouTube.

Link to original page on YouTube.

[sowega]

Originally Posted by TheDuck

Yep, I sold the old one for $50 and its been working great!

Awesome. I have to keep the stock airbox per class rules, so it'll be interesting to see how much clearance we can get.

I was within 2-3 cm of dragging hard stuff at my last track session, so I can't wait for the extra ride height!

[sowega]

I couldn't make the shock work without seriously cutting up the airbox, so I'm going to keep an eye out for an Elka or Ohlins on ebay.

If anyone (who isn't racing WERA) wants to try this, I have a shock that's already been grinded down and drilled out to fit the 250.

[nebraskan]

i take it those are pet ducks? haha not on topic, but if they are hows that going for ya? i kinda want one.

[HoneyBadgerRy]

@TheDuck do you have a yotube channel?