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I finished this up today. The bike definitely sits higher in the rear. To my surprise I didn’t miss any screws. Wanna make sure I have the shock collars correct, I swapped the left and right side. Pics below.
 

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I like the way the bike feels with the rear a little higher. Took me the better part of a days ride to get used to it though. I kept turning in too quick and lean angle would drop in too fast and I would have to adjust my line. This shock swap is the best thing you can do for the little ninjas. Super cheap and a very good improvement
 

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It looks like some things are on sale on eBay, so I just grabbed a low mileage GSXR 600 shock for under $30 shipped. I currently have a Penske 8981 on my 500, which ideally I'll have refreshed and swap the bottom mount to work with the 400 (clevis vs. eye). Until then, I've got a cheap upgrade to play with (and the Penske is admittedly overkill for me anyway). I'm not looking forward to flipping the upper shock mounts, but I'm sure it'll just take a bit of time. It can't be any worse than some of the other mods I've done...

According to Norton's spring rate chart, I actually need a bit stiffer than stock for my weight. However, comparing their numbers to RaceTech's (and just knowing the goal of Norton), I would assume those numbers are more track-oriented than street. Therefore, sticking with the 600's 10.1 spring (very close to stock) will probably work well for me vs. the 750's 10.5.

Unlike some of the older little Ninjas, the springs on the 400 seem to be fairly stiff from the factory - about 18% stiffer in the front and 11% in the rear compared to the NewGen 250 (and I believe the 300 kept those spring rates). It's a notch or two soft for a bigger guy like me, but my '09 EX500 needed about 70% stiffer springs at both ends to match my weight, for some comparison. It was nice to get on my new bike and have the OEM suspension behave pretty reasonably.

Based on Norton's chart, the stock fork springs are good for about 150lb and the rear is more like 205lb. I expect a lot of you smaller guys would do ok with the stock fork springs, but may want to soften up the rear.

I'm not sure if the earlier gen GSXR springs will directly swap to the current gen shocks, but you may be able to buy a second cheap shock to use as a spring donor. Here's the info I compiled a while back after digging around RT's calculator, forums, etc. I always strive for accuracy, but I've never personally tested (or even touched) any of these, so YMMV. The listed rider weights are based on Norton's chart (and me fudging the numbers up and down a bit for in-betweens), nothing else. It's just meant to give you a rough idea of what spring matches your ungeared weight.

Code:
BIKE MODEL	RATE (kg/mm)	RATE (lb/in)	RIDER (lb)
EX500 OEM 	5.4         	300         	X
EX250F OEM	7.9         	440         	X
EX250J OEM	9.3         	520         	X
EX400H OEM 	10.0         	560         	190-220

98-00 GSXR600	6.4         	360         	90-120
01-03 GSXR600	8.0         	450         	120-150
04-05 GSXR600	7.6         	425         	115-145
06-09 GSXR600	9.4         	525         	170-200
11-13 GSXR600	10.1         	565         	195-225

00-03 GSXR750	7.2         	400         	95-125
04-05 GSXR750	7.3         	410         	100-130
06-07 GSXR750	9.5         	530         	175-205
08-10 GSXR750	9.5         	530         	175-205
11-13 GSXR750	10.5        	590         	210-240

01-02 GSXR1000	7.7         	430         	115-145
03-04 GSXR1000	8.6         	480         	135-165
05-06 GSXR1000	8.1         	455         	125-155
07-08 GSXR1000	10.1        	565         	195-225
09-11 GSXR1000	11.6        	650         	240-280
For example, thegenius46m may have been able to use the spring off an '01-'03 600 or an '05-'06 1000 instead of buying one from RT. And while metal does fatigue, I'd be much less worried about buying an old, questionable shock/spring if I was using just the spring and not the shock.

Hopefully this helps people out, and we can get some reports on how swappable and appropriate the springs from other shocks are. I'm sure some of you have access to other GSXR shocks and/or are willing to spend a little bit on eBay to try out other options.

And just for easy reference, you can find the Spears Ride Height Adjusters at https://www.spearsenterprises.com/product/variable-ride-height-adjuster-for-kawasaki-ninja-ex400/, if you'd rather go that route instead of flipping the stock mounts.
 

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I think we also need to take into account the length of the springs as well, and not just the rates.

2012 GSX -R 600 has a 195mm spring length, but the 2003 GSX-R 600 has a 210mm spring length, according to the replacement springs by K-tech.
2005 GSX-R 1000 appears to have a spring length of 195mm also even though the eye to eye is different.

I went ahead and matched up the lengths with what you posted, I also find it interesting for example that the GSXR 1000 spring lengths all stayed the same except 07 and 08 which shortened by 10mm then went back to 195mm....


Looks like for these 600 shocks we need to stick with the 195mm length spring.
Also looks like the 600 and 750 springs, 06 and up would work as they are the right length.
The 1000, anything but 07-08 would work.



600

98-00 GSX-R 600 = 210mm
01-03 GSX-R 600 = 210mm
04-05 GSX-R 600 = 210mm
06-09 GSX-R 600 = 195mm
11-13 GSX-R 600 = 195mm
14-19 GSX-R 600 = 195mm


750
00-03 GSX-R 750 = 210mm
04-05 GSX-R 750 = 210mm
06-07 GSX-R 750 = 195mm
08-10 GSX-R 750 = 195mm
11-19 GSX-R 750 = 195mm


1000
01-02 GSX-R 1000 = 195mm
03-04 GSX-R 1000 = 195mm
05-06 GSX-R 1000 = 195mm
07-08 GSX-R 1000 = 185mm
09-16 GSX-R 1000 = 195mm
 

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I think we also need to take into account the length of the springs as well, and not just the rates.

2012 GSX -R 600 has a 195mm spring length, but the 2003 GSX-R 600 has a 210mm spring length, according to the replacement springs by K-tech.
2005 GSX-R 1000 appears to have a spring length of 195mm also even though the eye to eye is different.

I went ahead and matched up the lengths with what you posted, I also find it interesting for example that the GSXR 1000 spring lengths all stayed the same except 07 and 08 which shortened by 10mm then went back to 195mm....


Looks like for these 600 shocks we need to stick with the 195mm length spring.
Also looks like the 600 and 750 springs, 06 and up would work as they are the right length.
The 1000, anything but 07-08 would work.



600

98-00 GSX-R 600 = 210mm
01-03 GSX-R 600 = 210mm
04-05 GSX-R 600 = 210mm
06-09 GSX-R 600 = 195mm
11-13 GSX-R 600 = 195mm
14-19 GSX-R 600 = 195mm


750
00-03 GSX-R 750 = 210mm
04-05 GSX-R 750 = 210mm
06-07 GSX-R 750 = 195mm
08-10 GSX-R 750 = 195mm
11-19 GSX-R 750 = 195mm


1000
01-02 GSX-R 1000 = 195mm
03-04 GSX-R 1000 = 195mm
05-06 GSX-R 1000 = 195mm
07-08 GSX-R 1000 = 185mm
09-16 GSX-R 1000 = 195mm
I was looking at the spring diameter on the Racetech web site for the 06-10 GSXR 600/750 and it looked like they are different.
 

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I was looking at the spring diameter on the Racetech web site for the 06-10 GSXR 600/750 and it looked like they are different.

The diameter, or length?
And what number did you find at Racetech?

Cause I could not find length on Racetech's site and the diameter of the spring could be different depending on how they achieve the higher rate.

There are a couple ways you can achieve a tenser spring, the ones I know of would be

1. More coils over the same distance

2. Progressive spring, where one end has more coils tightly packed in a very short distance, and then normal spaced coils elsewhere, but the spring itself has the same overall length

3. Make each coil much thicker in diameter.

4. Use a stiffer material that does not contract as much under load

5. Make the spring longer, but compress it into the same space as the shorter spring, but with this method you have way more static force applied to a stationary object, so the spring is never relaxed, but always preloaded. I think this causes spring fatigue over time.

Firearm owners who keep their magazines fully loaded for many years without regular cycling swear against this possibility, and maybe in that application its not enough to cause feeding issues but the spring is definitely loosing slight amount of its tension I would think.

For the 2010 GSXR 600, here are the length and diameters of the spring at the upgraded rate 100n(10.2 kg/mm)
 

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Cool thanks, that helps our cause...........not sure how I missed that when I looked

So they are saying 178mm from Racetech, so I wonder who is right........

Let me measure my extra GSX-R shock and see what stock is...try to get the collars all the way out.....

This shock is off a 2016 GSX-R 600....I checked Race Tech who says 11-15 is the same.

I took the collars all the way out, the top collar I removed all the way, the one holding the spring, or compressing it, I took it all the way to the point I could easily rotate the spring on the shock itself by hand.

I measured twice with a digital caliper, once from the top to the bottom and the other way bottom to top from the flat sides of each end that rests on the collars, I measured:

191.94 mm and 191.42 mm

To me, that says the 195mm looks closer than 178mm, which I am not saying the 178mm will not work, but you might have to move those collars a ways down to get it preloaded good......

I think the earlier GSX-R's at 210mm will be too long to thread the collars without compressing the spring first with some spring compressors, then the thing will always be preloaded pretty darn good :)
 

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Cool thanks, that helps our cause...........not sure how I missed that when I looked

So they are saying 178mm from Racetech, so I wonder who is right........

Let me measure my extra GSX-R shock and see what stock is...try to get the collars all the way out.....

This shock is off a 2016 GSX-R 600....I checked Race Tech who says 11-15 is the same.

I took the collars all the way out, the top collar I removed all the way, the one holding the spring, or compressing it, I took it all the way to the point I could easily rotate the spring on the shock itself by hand.

I measured twice with a digital caliper, once from the top to the bottom and the other way bottom to top from the flat sides of each end that rests on the collars, I measured:

191.94 mm and 191.42 mm

To me, that says the 195mm looks closer than 178mm, which I am not saying the 178mm will not work, but you might have to move those collars a ways down to get it preloaded good......

I think the earlier GSX-R's at 210mm will be too long to thread the collars without compressing the spring first with some spring compressors, then the thing will always be preloaded pretty darn good :)
For both GSXR model series RaceTech require adapters which is what made me think they might be different diameters, the adapters might compensate for length also. Look on the screen shot for the line "Adapter Collars" the required adapters have numbers that might be dimensions for adapting length or diameter or both.
 

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For both GSXR model series RaceTech require adapters which is what made me think they might be different diameters, the adapters might compensate for length also. Look on the screen shot for the line "Adapter Collars" the required adapters have numbers that might be dimensions for adapting length or diameter or both.
Yeah I also notice they call it "Intall" yourself, lol

I like Racetech, but I sometimes question the accuracy of their data.......
 

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Keep in mind that the free length of the spring doesn't really matter, as long as the preloaded length is within the operating range of the shock you're putting it on. The PreGen 250's stiffer spring is about 1/2" shorter than the 500's, but it'll still just barely reach with the preload adjusted to match the weight of a rider who should be using that spring rate.



The earlier Ninjette springs are very small diameter, so it was hard to find aftermarket springs that would fit even just to get a cheap respring on the crappy OEM shock. As someone mentioned from the RT page, their springs often require mounting adapters because they're industry standard spring sizes, not exactly matched to the OEM shocks. The PreGen and 500 OEM springs were the same oddball diameter, and it happened to be a desirable rate too, so it works well as a cheap drop-in spring. If it were much shorter, you wouldn't be able to crank the shock down enough to actually hold the spring securely.


But as long as your desired preloaded length falls somewhere in the normal range of the shock's preload adjuster, it'll work just fine. I've spent like 5 minutes total looking at my new GSXR shock, but even the 15mm difference between certain years might not be an issue. The 25mm between the shortest and longest is probably pushing it. If the spring is too short, you won't be able to secure it on the shock; if it's too long, you won't be able to get it on the shock at all, or without preloading it way too much.
 
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Keep in mind that the free length of the spring doesn't really matter, as long as the preloaded length is within the operating range of the shock you're putting it on. The PreGen 250's stiffer spring is about 1/2" shorter than the 500's, but it'll still just barely reach with the preload adjusted to match the weight of a rider who should be using that spring rate

But as long as your desired preloaded length falls somewhere in the normal range of the shock's preload adjuster, it'll work just fine. I've spent like 5 minutes total looking at my new GSXR shock, but even the 15mm difference between certain years might not be an issue. The 25mm between the shortest and longest is probably pushing it. If the spring is too short, you won't be able to secure it on the shock; if it's too long, you won't be able to get it on the shock at all, or without preloading it way too much.

Right, I agree, and exactly my point. I would say all the 1000 springs are good to go, the 600 and 750 springs anything 2006 and above is good.

As I stated earlier in one of my replies, the 210mm spring on the 03 600 and 750 is going to really push it, once you get it on and the two collars started with enough threads to hold and not shear the threads off the aluminum collars that spring will already be pre-loaded so far any further adjustment is going to be beyond that usable range for sag unless your pushing 300+, and even then depending on the springs rate.


I think the earlier GSX-R's at 210mm will be too long to thread the collars without compressing the spring first with some spring compressors, then the thing will always be preloaded pretty darn good :)
Racetechs are perfectly fine, especially with their collars or spacers. I would also say the K-Techs are fine.

Yes, I owned more than one first gen/style Ninja 250 and a 500 once way back in the day, the 250 spring was a paperweight at best there was no point trying to upgrade the shock over replacing it with something else, 500 seemed no better so I never messed with either.

I try to do all my calculations and analyzing on paper and in my head, because it never seems to work out spot on the first time, so if I can reduce the number of parts I have to source off eBay and the times I have to take something apart and put it back together or modify it, before the testing phase, the better.
Especially if the difference in a GSX-R 600 shock from 2008 and a GSX-R shock from 2003 is, the 08 shock in good condition will be easier to find and probably cheaper than some old beat up clapped out 03' shock :)

I mean heck, if we really want to get into it, we can use any shock off anything so long as the diameter of the shock will clear the shock body, not interfere with the suspensions range of motion(including swingarm, dogbones, etc. of the motorcycle), and come close to resting on the collars of the shock body squarely/uniform to not bind or twist strangely, and then cut enough coils off it and use that. :D
 

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Thanks to everyone so far, I think everyone else, if they read these thread in its entirety and gather info into a spreadsheet(which I started but gave up on, lol) could easily buy a cheap 2011 and up GSX-R shock, and a 07, 08 750, 600 or 1000 shock and then replace the spring to get a rate that works for them, and have maybe $60-100(or $150-200 if you buy a RaceTech or K-Tech spring new) in the whole thing and knock it out over a weekend(couple hours for those with experience and done this before), without all the extra parts and headaches some of us went through to get this far.

Good job everyone and great job Scook for being the front runner!
 

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Discussion Starter #180
Does anyone have GSXR OEM spring rate info other then from RaceTech? I always take their online info with a grain of salt. The K-Tech rep I spoke with stated the N4 OEM spring rate is higher then the '11+ GSXR OEM spring rate. Not sure about 600 vs. 750 spring rates.
 
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