Date: 28-03-24  Time: 21:22 pm

Author Topic: FZS 600 suspension upgrade  (Read 6157 times)

tommyardin

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FZS 600 suspension upgrade
« on: 29 December 2016, 05:42:28 pm »
Hi Guys,
I have been working on my suspension of late and have done a few significant modifications to both the front and rear ends.
The Rear Modifications:
Firstly I purchased a new Nitron rear shocker, it was built with the correct spring and settings for my riding weight and riding style.
Whilst replacing the shocker I stripped out the linkage and cleaned all the needle bearings and repacked with grease, I was surprised as there was still quite a bit of the original grease still in the bearings, they were showing no sign of wear   :-)


 The Front Modifications:
For the front forks I purchased a pair of YSS Cartridge Emulators from Wemoto.com.
(YSS Model PD310 for the 2002-2003 FZS 600 Fazer)
To facilitate the operating of the Emulators the Damper Rods need to have more holes drilled through them to overcome the damping effect of them. YSS recommend that 6 X 8mm holes be drilled in them to achieve this.
I went a slightly different route because the damper rods on the 2002-2003 FZS 600 are shorter (190mm) than the earlier Boxeye model (210mm), I was concerned about encroaching on the upper chambers of the forks when the forks are on full compression by drilling the 3 X Double (6) 8 mm holes. 3 X 8 = 24mm, plus 2 X 10 mm minimum spaces between holes = 44mm extension up the damper rods.
(using the centre of the original damper hole as a datum point)
I opted for 2 X Double (4) 10mm holes with one 15mm spacebetween them = 35mm, also to give me a little more lea way I used a fine chain saw file to lower the original 5mm damper hole centre by another 3mm, before drilling the 10 mm holes. 2 X 10mm = 20mm, plus 1 X 15mm space = 35mm, and as I had lowered my starting point by 3 mm, the extension up the damper rods is now 32mm as opposed to 44mm.
 
The general settings for the YSS Emulators is two full turns in (For lighter (?) togged rider) on the Emulator adjusting screw from initial emulator spring contact with the valve, I set mine to 3 full turns as I am 88-89 Kilos togged ready to ride (14 Stones).
This setting I am fairly happy with although 3.5 turns might have been better coupled with 15 weight Silkoleen Pro Fork oil.
Whilst doing this work I replaced the original Yamaha progressive fork springs with Ohlins 8.5 N/mm linear springs, again more suited to my weight. 
 
The Outcome:
Firstly I am really pleased with the overall improvement with the bikes handling, I have heard terms like ‘The bike feels more planted’ and ‘I feel more confident cornering now’ and that ‘The bike turns in better now’ and to be honest I think the terms that have been used are accurate.
There is a twisty bumpy lane near me (1/3rd mile Rat Run) that has quite a few holes and uneven surface areas (Not fair to call them Potholes) but it’s a lane that I ride at about 35 - 40 MPH because it shakes the crap out of me and because I know that the bumps and pits are coming up I tend to brace myself ready for them (Wrong, I know) and the bumps travel up the forks and give me stick in wrists, elbows and shoulders and generally p----s me off.
I found myself riding down said lane the other day at about 50 mph thinking to my self could go faster,
Of course I was still feeling the bumps, but, they are not jarring anymore and the bike feels much more stable.
Since then I have taken the bike out on the infamous A272 in Hampshire (Petersfield to Winchester) a sweeping road that is great for biking, (Be warned speed cameras are a regular feature along its length) 
I have noticed that powering hard out of corners the forks tend to feel as if they topping a bit, so I may need to replace some of the fork oil with a higher viscosity oil or is that lower?, to stiffen/slow up the rebound as bit. This should also help with the compression damping and might mean I have no need to adjust the emulator setting by another ½  a turn.
I have 30 weight Silkoleen Pro fork oil on order. I will replace 100ml of the 15 weight with 100ml of 30 and see how that feels, I understand this to be fine tuning.
I feel that this a worthwhile mod and I also feel that it has been a great improvement to the bike, not just the handling but also the comfort.
The only setback is that without purchasing another set of Damper Rods this is an irreversible mod.
 
There are often sets of Fazer FZS 600 forks on eBay for sale, and if they are bent in some ways so much the better as they will be cheaper. The stanchions usually bend from the point where the stanchion enters the bottom sliders so the damper rods should be unaffected.
 
There is always a disclaimer with any information or advice:
Anyone doing this mod, especially the front forks does so entirely at their own risk.
I have only put pen to paper (Finger to keyboard) as an information sharing exercise and not as a guide or a recommendation to anyone.
 
One last thing.
Some say there are better and financially cheaper ways of improving the rear suspension.
There is a member on FOC-U (DevilsYam) that can supply you with a modified R6 mono shock to fit your Fazer and he will set it up for your weight and riding style, he also will supply the necessary dog bones and fitting instruction for considerably less than I paid for my Nitron Mono shock.
You might find you can save yourself a small fortune.
 
There is nothing wrong with the Nitron but it is pricey.
There is also a serial front suspension moder on here (Kebab19) You can search for his advice on the front fork mods.
I have used his advice in the fork mods that I have done.
I am now looking forward to seeing those 5/8 inch chicken strips on my back tyre slowly diminishing.
tommyardin

« Last Edit: 29 December 2016, 09:00:32 pm by tommyardin »

vinnyb

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Re: FZS 600 suspension upgrade
« Reply #1 on: 09 April 2017, 10:28:03 pm »
 Hi Tommy, just been reading your post regarding the YSS cartridge emulators and I am thinking of going down the same route. I was just wondering how the setting up was going. Have you managed to get it about right yet or are you still experimenting with oil weights and air gaps etc? Do you feel that it was the new springs or the emulators that made the biggest difference or the combination of the two? I ride two up regularly and wonder if I would be removing my caps and springs to fiddle with the emulators or just adjusting my preload on top of the forks. Any advice or set up tips would be appreciated, cheers

tommyardin

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Re: FZS 600 suspension upgrade
« Reply #2 on: 10 April 2017, 01:11:54 am »
I am really glad that I did all the mods that I did, to be absolutely honest the linear springs made a huge difference to the front.
I have heard it said, and I have said it myself that the original FZS 600 springs are progressives, in fact the springs that came out of my FZS 2002 model (2003 Registered) were not progressive they were dual rate springs.

See photo of original dual rate spring and the new Linear side by side.

Looking at the the dual rate spring you can see the point where the spring rate changes, just over half way up, that is the problem with the original springs if cornering at speed and you hit bumps the spring rate can change dramatically, changing the geometry of the bike and effect the steering.
Linear springs are as the name implies are single or linear rate, to compress the spring 1 inch it takes X force, to compress the spring 2 inches it take two times X force and so on, makes for a predictable and more controlled ride.

You can see that the Linear springs are just a tad shorter than the original Dual Rates springs, this difference was made up by the YSS emulator making up the difference, in fact I had to cut 5mm from the top fork spacers to get back to the right length. If I had fitted the same Ohlins springs without the emulators I would have had to get some slightly longer spacers made up (Any engineering works could do that for around 40 quid)

If I bought another FSZ 600 I would do most of the work again but this time I would try without fitting the emulators, I would put good quality Linears in that match my fully togged up riding weight (And play around with fork oil weight) and then have a chat with Devilsyam with view to purchasing one of his R6 shocks.

This way I am guessing that you could do the work for about £300 maybe a little less, and the bike would handle a lot better than the standard FZS, but to be honest the Standard FZS is not a camel, but it can be improved.

Ohlins are a very good spring. the ones I fitted were for a Suzuki SV 650 rated at 8.5 N/mm, which suited my rider weight fully togged in all my riding kit I am a couple of pounds under 14 stones/ 12.75 stones in my birthday suit (Don't go there).

To be honest I don't really think that a female pillion would make that much difference to the front end, but she would effect the back much more, but some of that can be sorted with the pre-load on the mono-shock. Again to be honest the is no perfect set up for suspension if some times you ride solo and some time with a pillion or a load of luggage.

When I bought my Nitron R1 shock Nitron wanted to know my togged rider weight, whether I carried a pillion and how often, how much the togged pillion weighed and also my riding style and they built my shock with the right spring for my requirements, so it's a compromise really, the only time it's not a compromise is when it is done for a raceing bike or track day only bike as everything is a done deal and a know weight then.
I ride sometimes with my 23 year old daughter on the back and to be honest it does make the bike a bit softer on the back end but can't say I have noticed any difference at the front end, but there again my bike is set up on the slightly harder side as I like to go hooning once in a while.

Again the Nitron R1 is a great shocker but at 450 quid it really is a shocker, my guessing is that Devilsyam R6 shocks are likely to be a lot less and equally as good if not better.
My upgrade set me back about £600, but as said earlier I think it could be done going a slightly different route for half and not fitting the emulators.
If you decided to do the emulators they could be done as a project for another time.

Let us know your thinking on it all and decisions if any. :thumbup
« Last Edit: 10 April 2017, 01:12:38 am by tommyardin »

vinnyb

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Re: FZS 600 suspension upgrade
« Reply #3 on: 10 April 2017, 08:33:20 pm »
 Thanks for the info Tommy, it looks like I've got some decisions to make. My main problem is the harsh feeling when I'm riding along bumpy roads. Backing off the preload helps the harshness but leaves the forks a bit squidgy. I'm looking for a comfortable controlled ride, rather than track day handling. I'm trying to decide whether to go for emulators and linear springs or progressives and 15W oil. At 85 quid, Hagon progressive springs are obviously the cheaper option but is it money down the drain? Maybe try them first and see how they are and if I'm not happy I flog 'em for whatever I can get for them and go down the emulator route. Then to sort out the back end but I feel the front is worse than the back at the moment. Any opinions would be gratefully received.

tommyardin

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Re: FZS 600 suspension upgrade
« Reply #4 on: 10 April 2017, 09:49:29 pm »
What ever you put in the front will be a vast improvement over the dual rate jobbies that are in there at present, the problem with emulators is there is no way back without acquiring another set of Damper Rods,  and that will most likely mean another set of forks from eBay to retrieve them from.


My suspension is still on the firm side of plush, but that is the way I wanted it, with my daughter on the back it does soften the ride, but it still absolutely fine, just slightly softer.
I think I paid £118 for the Ohlin's Linears, but I have read on this forum guys who have put progressive in and been really really pleased with the ride saying stuff like the bike is more planted and also the harshness has gone.


I think with the Yamaha springs it is probably the second spring rate coming into play that tightens up quickly and causes the harshness, progressives should overcome that, because the rate changes progressively and not with a sudden step, unlike the Yamaha forks springs as they compress and hit the harder rate.


I know Graham on here had new springs fitted and he was convinced it completely focced his handling up, my guess is that they were not fitted very well.


With the damper rod suspension you are relying on the fork oil being pushed through a very small single hole (about 5mm) at a fast rate of knots as the forks compress rapidly after hitting a big bump, if the oil is to thick to pass through that hole quick enough to allow the forks to continue on their downward journey you get something called Hydro lock, which can feel as if the forks have bottomed out and really jarring your wrists and shoulders, but it is just that the oil can not pass through the damper hole quick enough and locks up the forks.
If you try the progressive springs don't use a to heavy fork oil because if you need to go heavier with a syringe and a piece of small bore piping (Fish Tank air line)  you can draw a measured amount out and replace that with a heavier oil, untill you are happy with it.


Someone explained Hydro lock to me like this: If you have a child's water pistol and yank the trigger in as fast as you can the trigger will jam because the water cannot get out of the pin hole fast enough, = to thicker oil, best to start with a thinner oil and gradually draw a measured amount off and replace it with some thicker oil, if necessary.
Good luck, I will be interested to hear which way you go.  :thumbup


PS: I am no expert by any means I have learned and understood from guys on here who have been very helpful to me, but that is the I guess that is the way we all learn.
« Last Edit: 10 April 2017, 09:55:04 pm by tommyardin »

vinnyb

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Re: FZS 600 suspension upgrade
« Reply #5 on: 10 April 2017, 10:24:02 pm »
 After rereading your post it seems that linear springs, new 10W? oil and no emulators is the way you'd go, learning from what you'd done already. Am I correct?  I understand what you say about the damper rods being irretrievable if you don't like what you've done. Progressives seem to sort one problem but create another from the reviews I've read on various forums.
« Last Edit: 11 April 2017, 05:14:49 am by vinnyb »

vinnyb

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Re: FZS 600 suspension upgrade
« Reply #6 on: 10 April 2017, 10:32:41 pm »
Wondering if we should continue this on the fzs600 section instead of introductions?