ZR7 Rear Shock Conversion

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Mere
Posts: 153
Joined: Sun Feb 25, 2018 7:28 pm

ZR7 Rear Shock Conversion

Postby Mere » Fri Mar 01, 2019 7:52 pm

I have finally sorted out my bike's suspension and fitted a Kawasaki ZR7 rear shock :D . My GPZ 500 is a good bike but it had become very noticeable that rear shock was not working properly at 19yrs /29k. The shock was not damping resulting in a nervous bouncy ride, especially so on twisty roads which should be fun on any bike! Spending £250-300 on a new shock was probably going to be out of my budget.

What to do? The choices appeared to be:
1) Fit another GPZ 500 shock
2) Fit an EX250/300 shock
3) Fit an SV650 Shock
4) Bite the bullet and purchase a new Shock – YSS / Hagon

Each was not without issue though:
(1) As likely to be no better (or perhaps even worse) than what I have.
(2) Same as (1) but harder to source and possible centre-stand issues with the reputedly longer EX300 shock.
(3) Said to work well but I was not keen on modifying (drilling / spreading / filing) the clevis to maintain the use of the centrestand. Have I mentioned that I like a centre-stand on a bike?!
(4) Still out of budget!

There had to be another option............
After a bit of web research, involving reading posts on the EX500 US website, a forum member there (po18guy) had fitted a ZR7 shock to his first gen bike, all appeared good but at the time he had not managed to complete a test ride so still very much unknown. He had commented that the spring was a thicker gauge so may suit 2-up riders more. The ZR7 is a 25kg heavier bike than the GPZ and is considered softly sprung so I was optimistic that it might just work out. He had taken some good pictures and measurements etc which encouraged me. I liked the look of the shock; the spec was good with adjustable damping and a quality alloy clevis. What impressed me even more was the fact that the shock damper was shrouded with a plastic sleeve to protect from road filth. What a good idea! As it is not possible to fit a hugger onto the GPZ this is an obvious improvement. So here was option 5 and I decided to start looking for one.

I eventually found a shock, on ebay from a private seller, no obvious faults stated apart from it being a bit rusty (actually no worse than my existing shock). The price of only £25 delivered sealed the deal for me.
zr7_1.JPG
Once delivered I was impressed with the overall quality. Same length as the original with a thicker wider spring ( see picture). The top eye width is (strangely) 2mm narrower (I was aware of this issue from the EX500 site post). I de-rusted and neutralised the corrosion, and polished/painted as required. After 2-nights I had a good looking shock! Would it fit though?
zr7_2.JPG
zr7_3.JPG
Lingering doubts as to whether this would fit a gen2 bike with its slightly different swingarm were playing on my mind. I offered it up and..... it fitted through the swingarm gap! This was a relief! To cope with the 2mm narrower shock mount a 1mm shim washer is required each side of the eye. I used a dab of grease to hold in place whilst using a trolley jack to slowly raise the shock into place. Probably the fiddliest part of the whole job. Longer bolts and spacers are also required respectively to space out the linkage rods approx 7mm each side (to clear the wider spring) and to cope with the shock's wider alloy clevis. Whilst the bike was partially stripped I set the shock preload to position 2 of 7 and the damping to position 2.
zr7_5.JPG
zr7_6.JPG
Once fitted it was immediately obvious that the bike was far less 'saggy' with a positive 'firm' feel, I measured the shock free movement to be circa 3.5cm (without riding gear on) which for me at 75kg / 11.5 stone plus the added weight of boots /leathers/helmet should be OK. Use of the centre-stand is unaffected by the shock – the rear wheel is raised off the ground by 2cm or so. A biking mate looked it over and confirmed that the bike 'looked right' and 'sat well'. Good enough for me!
zr7_7.JPG
I initially test rode on my 7 mile fast 'A' road commute to work and am happy to report that the bike is completely transformed. The shock has given the bike a secure planted feel with a plushness that makes it feel like a new bike! The bike was then MOT'd with no advisories made. All good!

A longer 125 mile mixed route ride has further confirmed this with no degradation of the shock's damping once warmed up. Obviously this used ZR7 shock must have some wear but even allowing for this, in my opinion, this shock performs superbly on the 25kg lighter / different unitrack set-up GPZ. Recommended!

Below is a shopping list for those who may be tempted, best regarded as a rough guide as we all do things differently, usual caveats apply and you modify your bike at your own risk.

Kawasaki ZR7 Shock – shrouded damper with the RED spring (1999 -2004). A rusty (i.e. cheaper) one can easily be renovated as described. Same M12 bolt diameter as standard for both top-eye and clevis, longer bolts are needed though. Standard Kawasaki bolts are M12 x 1.25, closest I could readily purchase to the right strength spec are M12 x 1.5.

Linkage bar bolts required – M12 x 1.5 x 120mm........................... x 2 required
Linkage bar alloy spacers M12 x 5mm …..................................... x 4 required
Shim washers either side of the spacers M12 x 1mm....................... x 4 required
Shock clevis bolt – M12 x 1.5 x 70mm …....................................... x 1 required
M12 x 1.5 Lock Flange Nuts …...................................................... x 3 required
M12 x 1mm top shock eye shim washers …................................... x 2 required
M12 – washers fitted to bolts/nuts ….............................................x 6 required

john
Posts: 3965
Joined: Wed Mar 26, 2014 6:48 pm

Re: ZR7 Rear Shock Conversion

Postby john » Fri Mar 01, 2019 8:19 pm

Congrats on that, well done.
This is another shock option for us all, and, a bloody good write-up with actual "on road" riding report, as well as a parts list for anyone else doing it.
You've done a really good job re-furbing that shock as well, it looks like new.

yorkie-col
Posts: 1584
Joined: Thu Feb 26, 2015 2:39 am

Re: ZR7 Rear Shock Conversion

Postby yorkie-col » Fri Mar 01, 2019 9:43 pm

good write up. well done. nice job there mate. however I doubt this conversion could be done on a gen 1 without major modifications to the swing arm, because the hole where the shock goes through is a lot smaller the SV650 shock only just fits in and is no where near as wide as the ZR7 plus the dog bones on the gen 1 are preformed not flat plates on one end is bushed and fits in a socket on the swing arm so cannot be made wider without some degree of engineering. you could do this by changing out the gen 1 swing arm for a gen 2 one and using all the gen 2 bits, but that adds a lot of cost to the conversion.

john
Posts: 3965
Joined: Wed Mar 26, 2014 6:48 pm

Re: ZR7 Rear Shock Conversion

Postby john » Sat Mar 02, 2019 6:19 pm

yorkie-col wrote:
Fri Mar 01, 2019 9:43 pm
good write up. well done. nice job there mate. however I doubt this conversion could be done on a gen 1 without major modifications to the swing arm, because the hole where the shock goes through is a lot smaller the SV650 shock only just fits in and is no where near as wide as the ZR7 plus the dog bones on the gen 1 are preformed not flat plates on one end is bushed and fits in a socket on the swing arm so cannot be made wider without some degree of engineering. you could do this by changing out the gen 1 swing arm for a gen 2 one and using all the gen 2 bits, but that adds a lot of cost to the conversion.
The cut out for the shock (the hole it goes through) is the same size on the 1st and 2nd gens, I've done SV shock mods on both. The 2nd gen swing arm differs in the way the dog bones are mounted to it, and the way the chain adjusters are fitted (inside). The overall arm length is 10mm longer to accomodate the 17 inch wheel, but dimensionaly they are the same....in fact, I fitted a 1st gen swing arm to the JPS when I swapped everything over to the 2nd gen frame.
I would need to see one in the flesh, and measure it up, but I see no reason why the ZR7 shock could not be fitted to a 1st gen,? just might need a bit more modifying.

Mere
Posts: 153
Joined: Sun Feb 25, 2018 7:28 pm

Re: ZR7 Rear Shock Conversion

Postby Mere » Sat Mar 02, 2019 6:45 pm

john wrote:
Fri Mar 01, 2019 8:19 pm
Congrats on that, well done.
This is another shock option for us all, and, a bloody good write-up with actual "on road" riding report, as well as a parts list for anyone else doing it.
You've done a really good job re-furbing that shock as well, it looks like new.
Many thanks & glad that you find the write up useful. I was determined to make it real world and almost a throwback to the bike magazines of the 80's who often ran articles in this style. The shock was fettled on the kitchen table (warm and easy!) in dark wet cold December, I matched the original shock finish with whatever metal paints I had left over from other projects. The weak point on the shock is probably the castellated pre-load adjuster as this acts as a 'trough' and holds water. Next time I do the linkage I'll probably fill this with bathroom silicone....maybe.
yorkie-col wrote:
Fri Mar 01, 2019 9:43 pm
good write up. well done. nice job there mate. however I doubt this conversion could be done on a gen 1 without major modifications to the swing arm, because the hole where the shock goes through is a lot smaller the SV650 shock only just fits in and is no where near as wide as the ZR7 plus the dog bones on the gen 1 are preformed not flat plates on one end is bushed and fits in a socket on the swing arm so cannot be made wider without some degree of engineering. you could do this by changing out the gen 1 swing arm for a gen 2 one and using all the gen 2 bits, but that adds a lot of cost to the conversion.
Many thanks. The EX500 post described and pictured this shock being fitted to a Gen1 but no test ride so unknown if it works OK. I'll measure the ZR7 shock width tomorrow, it may be wider (not by much I suspect) than the SV shock, none the less it fits and does not rub so all good!

john
Posts: 3965
Joined: Wed Mar 26, 2014 6:48 pm

Re: ZR7 Rear Shock Conversion

Postby john » Sat Mar 02, 2019 7:05 pm

I've been a member of EX500 for many years. I've seen a few posts by PO18guy, he's done a fair bit of modifying to his bikes. There are a few others on there as well who have done a lot of work on the 500, saabnut springs to mind, he's got/re-built a few of them, :lol:

yorkie-col
Posts: 1584
Joined: Thu Feb 26, 2015 2:39 am

Re: ZR7 Rear Shock Conversion

Postby yorkie-col » Sat Mar 02, 2019 7:58 pm

well I wouldn't want to contradict anybody. :oops: I have looked for the post on EX500 but could not find it so no idea how it was done.

as for the swingarm differences I too have fitted a gen 1 on the gen 2 and visa versa while playing around with shocks and dog bones to lower the ride height. I can say for definite the hole in the gen 1 is smaller forget the exact measurements probably 5mm the gen 2 it is also longer as John said but also wider to accommodate the disc carrier. it is one of the reasons I used the twin pipes on the cruiser the Motad is a fixed position system owing to it being welded several times. it would not fit the gen 2 swingarm on the bike without fouling the arm. but is perfect on the gen 1.

I have some photos somewhere of the first rebuild I'll see if I can find them. as for the ZX7 shock no idea of size but Danny [lunty74] tried to fit a ZX6 shock to his gen 1 and had to abandon the idea because it rubbed the arm and bones. if it is that wide it needs spacers on the bones to pass the spring then I can't see how it would fit a gen 1 with fixed position dog bones. sorry.

edit. found these. they aren't that clear on the differences though.

gen 1. with SV shock
061.JPG
gen 2 with SV shock
100_0876.JPG

Mere
Posts: 153
Joined: Sun Feb 25, 2018 7:28 pm

Re: ZR7 Rear Shock Conversion

Postby Mere » Sun Mar 03, 2019 10:44 am

Here you go, you need to be a member of Ex500.com to see this particular sub-forum, not that I ever post on the site generally , it seems somerwhat passive/aggressive so far as web forums go!

https://www.ex-500.com/34-racers/59562- ... nsion.html

Screen grab attached!
po18guy.JPG
Just measured the width of the ZR7 shock at 72mm or so - difficult to get the verniers on square when mounted....

Martinj
Posts: 964
Joined: Fri Jan 08, 2016 8:18 pm
Location: Doncaster

Re: ZR7 Rear Shock Conversion

Postby Martinj » Wed Mar 06, 2019 8:13 am

A really nice & tidy job, good write up too. A few of us are also members of the ex forum , although I personally have not been on there for a few weeks, whilst I’ve been working on the cx.
91 gpz500
79 cx500deluxe
Interceptor 650


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