Date: 19-09-17  Time: 16:22 PM

Author Topic: Kebab19's GOLD VALVE modification for FZS600 forks  (Read 9210 times)

John Silva

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Kebab19's GOLD VALVE modification for FZS600 forks
« on: 02 January 2011, 02:17:41 PM »
Originally posted by kebab19 on 20/09/2008


Short Q&A

Q: What's this?

A: This is a front fork modification for Yamaha's FZS600 98-03. It improves the feel of the front forks, particularly over bumpy roads but pretty much everywhere else too.

Q: Can't you just add Hagon springs & different oil?

A: Yes, and that works to an extent, but it does not alter the internal damping properties of the fork mechanism. Damper rod forks are by nature a compromise; bumps are transmitted to you in a fairly harsh fashion. Fazers (and almost certainly all other budget bikes) employ damper rod fork design, whereas the more expensive cartridge forks have an internal mechanism design considered much superior.

Q: So what have you done?

A: Taken Fazer forks and fitted Race Tech's Gold Valve emulators (and suitable linear springs) to make the fork comparable to a cartridge-damped fork. It will now be adjustable for high-speed and low speed compression in addition to rebound, unlike the standard setup.

Q: How much?

A: Depends how much you replace and what tools you have - £120 minimum, about £250 maximum. Breakdown as follows: £120 for the Gold Valves, around £80 for a pair of suitable linear springs. £10 or so for fork oil. £25+ for drill cutting stones, drill bits & a centre punch, angle grinder, jigsaw, big hammer……

Cutting stones

Q: Is there a catch?

A: The modification is permanent - as surgery is required you can't go back to the standard set-up unless you replace the fork's damper rods. You can get round this (as I did) by getting hold of a spare set of damper rods. You can of course modify the ones that are currently inside your fork legs, but if you mess them up you're in a world of poo. Someone on the site may have a pair for sale (thanks BrummyMax!) or Ebay 'Fazer breaking' ad may have the parts (bent legs). If you do this, you can convert forks back to standard if necessary.
Also, although a considerable amount of adjustment becomes possible, it requires changing oil level / thickness & fishing the emulators out of the forks to change their settings: however, this really is a minor inconvenience compared to the end result.

Q: How did you come up with this?

A: One of my previous bikes was a Yamaha TRX 850, another great bike that also suffered from a poor damping-rod fork design. After selling it on, I had a spare set of forks in my garage (pitted stanchions). I'd remembered reading that there were RaceTech products to improve the TRX's forks and that reviews of their Gold Valve kits had been very positive. I noticed that the TRX forks looked very similar to the FZS forks (apart from length), were also 41mm in diameter and both bikes apparently weighed the same. A bit of Haynes research using exploded diagrams showed that the internal front fork design also looked very similar, so I thought 'What if...?'

HOW TO DO IT

Disclaimer - offered for information only, if you have NO mechanical prowess then DO NOT attempt this mod! Either that or get a pro to help out…..

There are other threads on this site regarding how to remove forks/ change fork oil etc so I will assume anyone intending to do this already knows their stuff.

Order the necessary parts - I ordered mine from PDQ. You'll need a set of Race Tech Gold Valve Emulators part number FEGV S4101 for the Yamaha TRX850 at £119.99
I also ordered an optional pair of Race Tech linear springs with spacer material at £79.99, but you may be able to get by with Hagon springs or other makes. Race Tech advise against progressive springs for technical reasons I wont go into here, but IMO any aftermarket springs are better than standard! Might also be useful to get for preload caps off 2000 onward bikes (or remove them off TRX850 forks as I did).

Race Tech goodies

Acquire a spare set of front fork damping rods. As far as I know the rods from 98-03 remained unchanged so this mod should be applicable to them all. By the way, mine is a 1999 bike.

1. Bike up on front & rear paddock stands

2. Remove front wheel & brake callipers / lines off fork legs. Remove mudguard.

3. Loosen the fork leg top caps off very slightly (for easier removal later).

4. Loosen yoke pinch bolts & remove fork legs.

5. Loosen the 8mm allen bolt at the bottom of the fork legs. I added extra washers in under the fork top caps to increase preload; this stopped the damper rotating round with the allen bolt. Remove lower allen bolt & let the fork oil drain out (potentially messy).

6. If it still won’t come off, turn the fork upside down and use an impact driver to jolt the allen bolt loose. It helps to compress the suspension while doing this. If this doesn't work take the fork top cap off, drain oil, remove spacer & spring and then jam a broom handle in place to stop the damper rotating.
Anyway, what we want is the lower damping mechanism to separate from the bolt and for it to slide out.

7. Allow remaining fork oil to drain out of legs, usually takes an hour or two.

8. The damper rods have now to be altered. This is the important part!

Standard Damper

Remove (and keep safe) the plastic piston ring it will be refitted upon reassembly. Grinding with it in place might damage it. The Gold Valve emulators are meant to sit on top of the damper rods, but unfortunately they don't fit modification time!

The Problem!

9. You'll need to bore the top of the damper out by about 1mm and about 4mm deep using a drill & the cutting stones. Or for an easy life take it to an engineering company.
The emulator must sit tight & level on top of the damper rod, effectively blanking it off. Even though the fork spring will be compressing it down in place, I feel that if you're going to all this trouble, it's best to get it right!

Next we need to radically alter the existing damping setup. Leave the tiny rebound pinhole at the top of the rod untouched; the compression holes require surgery. You need to drill out the two existing compression holes at the bottom of the damper enlarging them to 8mm. In addition, you need to drill another four 8mm holes, making SIX in total. The intention is to kill off the old damping oil routes - the emulators will control oil flow instead. A Centre punch is great for starting the holes off - make sure holes are staggered and MORE THAN 10mm APART - less could cause the rod to fracture, and remember these rods bear the full weight of the bike, particularly under heavy braking. Make sure you leave the holes smooth inside & out (cutting stones again and circular file). Finally, ensure parts are totally clean with no fragments of metal anywhere.

Modded Damper

The complete setup should now fit together and look like this
Modded Damper & Gold Valve

10. Next, either make up or alter your existing metal spacers that sit on top of the springs. The emulators add about 12.5mm so either cut the spacers down to size by that amount or wind off your preload caps if there's enough adjustment. As I used TRX fork springs I had to make custom length spacers.

11. Reassembly time. Insert damper with small spring back in fork, add spring, spacer, washers & fork cap to create tension so you can reattach the 8mm allen bolt at the bottom of the fork leg. Tighten and use thread sealant, especially if you're not renewing the crush washer!

Ready to Reassemble


12. Remove top cap, washers, spacer & spring again. Now we insert the Gold Valve - it needs to be nut side down, allen bolt side up.

Gold Valve emulator in place


13. Once in place, pour about 250-300ml of your fork oil in. What weight to go for? Racetech mention ether 15W or 20W for the TRX forks. I'm about 73kgs so went with the lighter 15W oil. Now pump fork up & down (slowly, about 15 times) and enjoy the gurgling noises.

14. Now add remaining oil. How much in total? Well, I have again gone with data similar to the TRX. Their forks use 483ml per leg (early Fazer 475ml). The emulators displace volume, but exactly how much is unknown. Most TRX owners use about 440ml per leg, so just over 40ml less than standard. For the Fazer, I have started with 430ml - 45 less than standard. I realise that Fazer fork oil height is usually a critical setup factor, but the introduction of the emulators changes all this. Besides with no one else having tried this I had to start somewhere……

15. Add spring, spacer, washers and fork caps.

16. Reattach everything in reverse order - forks, mudguard, wheel etc etc and you're ready for action.

17. From now on, fork adjustment is done as follows.

17a. PRELOAD - Either change internal spacer length or adjust preload fork caps

17b. REBOUND - changing the thickness of the oil alters rebound characteristics. You could switch to 10W, 20W or mix oil for in-between settings. A bit tedious I know but eventually it will end up perfect for you!

17c. COMPRESSION - The emulators are set with a certain amount of preload (they are 2 full turns in, suitable for 'street use') - changing this preload will affect the amount of oil flow through them. In addition, oil height / level obviously still plays a part. Too little oil & the fork action will bottom out too easily. Too much oil & spring action will become very harsh especially near full compression. Experimentation is essential.
That's enough for now! Needless to say, I have started the long process of gathering precise data for my preferred settings, but they will only apply to my weight range (11.5 stone) and as everyone's weight and preference is different, there is no single miracle setting for everyone. I will update this thread when I have more info.

For anyone out there who feels their Fazer deserves quality front suspension, this is the best cure!
Oh, and finally thanks to Yamaha's TRX850, which has unwittingly provided a cure for the FZS600's fork damping.


Useful links
Race Tech's Gold Valves - Emulators explained
Gostar's suspension setup - Suspension setup
« Last Edit: 07 January 2011, 03:40:31 PM by John Silva »
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John Silva

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Re: Kebab19's GOLD VALVE modification for FZS600 forks
« Reply #1 on: 02 January 2011, 02:29:07 PM »
Originally posted by kebab19 on 21/09/2008


Testing commences

Due to a glitch in the Matrix, the weather here was dry and sunny for once, so I went for a 100+ mile spin with mate on his Superduke up the Antrim Coast area. Initial results are very encouraging, although some fine-tuning will be required.
 
The roads consisted of motorway, smooth-ish dual carriageway, then fast bumpy A roads and finally fast, smooth A roads.
 
Motorway and dual carriageway was first. My former bugbears, resurfaced patches and tarmac over banding no longer provided a harsh jolt throughout the entire bike. Instead I could feel the front raising slightly, but the impact wasn't transferred to the bars. Perhaps it's more accurate to say there was an awareness of going over road irregularities as opposed to feeling them. If anything, I felt more of a jolt through the rear shock, and it's a fairly good WP item.
 
On to the bumpy A roads. Again, through corners the new setup proved far superior to the original. On the standard setup, small bumps in corners deflected the front wheel off course, requiring constant correction. Now the front wheel seemed to be glued to the road, inspiring more confidence. Of particular revelation was braking hard before approaching a corner - I found myself braking much later because I wasn't as concerned about bumps.
The forks did however prove a fraction too soft for badly potholed roads, particularly beyond 80mph. Although I didn't know it at the time (keeping a Superduke in sight proved impossible) the forks were nearly bottoming out. I normally run the bike with my yokes dropped 10mm to quicken up the steering, possibly too much while I am still experimenting with this new setup. I stopped later at a chippy van for a cuppa and noticed scratches on the top of the mudguard underneath the brake lines. Obviously with the new setup there was more suspension travel and it was fouling the mudguard. For the journey home I increased the preload adjusters as a temporary fix. The fast smooth A roads home were enjoyable and incident free.
 
I have concluded that I may need a bit more oil in the forks (according to Race Tech, too low an oil level causes the forks to bottom out too easily) but am not sure how much. I will start with another 10ml in each leg and see how that feels. I will also raise the yokes back up 5mm as a safety measure to protect my front brake lines. All other suspension factors (fork oil weight, Emulator preload) all felt pretty much perfect from the off.
« Last Edit: 07 January 2011, 03:42:29 PM by John Silva »
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John Silva

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Re: Kebab19's GOLD VALVE modification for FZS600 forks
« Reply #2 on: 19 June 2013, 09:58:46 AM »
kebab19 has been busy on trying to prefect this mod.

http://foc-u.co.uk/index.php/topic,8366.msg82468/topicseen.html#new
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kebab19

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Re: Kebab19's DEBRIX emulator modification for FZS600 forks
« Reply #3 on: 26 August 2013, 02:49:49 PM »
For those about to attempt fork modification using DEBRIX emulators, it's a case of following the original Goldvalve instructions BUT WITH THE FOLLOWING CHANGES.

Follow steps 1 to 7 as before. Use the first half of this useful thread to get all fork parts out http://foc-u.co.uk/index.php/topic,42.0.html  & stop before taking off dust caps etc.

Step 8 - You can ignore this part, with the DEBRIX emulators you no longer need to grind out / widen the damping rods - they are a perfect fit for sitting on top of the damping rods.

Step 9 - You still need to enlargen the original compression hole, but you should drill LESS holes than the six I originally did. You push drill bit through the original hole & bore another hole out the other side of the rod. Then keep widening both of these holes with broader drill bits. If I were to do the mod again, I would bore the original compression holes out to 10mm & then drill two further 10mm holes higher up the rod (hole edges should be about 10mm apart). These holes should be staggered 90degrees round the rod to retain structural strength. To reiterate, DO NOT drill six holes, it's excessive as four larger holes will do the same job & going further up the rod reduces it's damping effect & weakens the rods. Also, it's been brought to my attention (thanks WEZDAVO) that the later bikes from year 2000 onwards have shorter damping rods, approximately 180mm instead of 200mm rods in the 1998/99 bikes, all the more reason to keep to only four holes!
Keep all holes AT LEAST 12cm /120mm below the upper wider 'lip' of the damping rod - the ruler in the picture below should hopefully indicate the 0-120mm area that you should NOT enter into while drilling holes. By the way, in the picture the small hole at the 2cm/20mm area is the rebound hole which you should leave alone.


















Step 10 & 11 as before.

NEW STEP - 11A - You'll need to set your DEBRIX emu's preload before inserting them into the forks. The allen bolt through the emulator is threaded at the bottom. To set preload on the emulator, take the bottom nut completely off, then loosen the allen bolt until it barely touches the washer / spring.
Then rotate the allen bolt to give preload between 2 to 4 full turns. The allen bolt head appears to be a weird size (possibly imperial?). You can use a Torx 20 bit in a screwdriver, or just clamp on vicegrips if you don't have anthing else useful to hand. The bottom nut can be unscrewed using a 9mm spanner.
Emulator preload:
SV650 owners suggest 2.5 turns so I went with that, 2.75 turns or 3 might be better if you are....big boned. 4 turns would be much more suited for the racetrack environment & probably way too harsh for our roads.  Once you have set allen bolt preload, hold the allen bolt steady in postion, put the bottom nut back on & tighten her up. Don't allow the top allen bolt to start moving once the bottom nut nips up - it's one of those nyloc jobbies that should stay in place. Sadly you'll need to fish the emus out of the fork oil if you need to make further adjustments, so give your preload setting a lot of consideration and you might set it up perfectly for your requirements first time around.

Step 12 & 13 as before.
 
Step 14 -  Regarding fork oil, go with height instead of amount. With emu in place, but fork springs, spacer removed & forks compressed, measure oil height from top of stanchion as you normally would if you were changing fork oil. The more oil you have in place, the firmer the final third of the suspension stroke will be. I would suggest removing some oil, start with oil height 10mm lower than standard & if still too firm progress to removing another 10mm and so on. Oil weight is optional, but most emu instructions I've read go with heavier than standard oil, either 15w or 20w or even a mix of the two to give 17.5w. I went with 15w Yamalube fork oil but it's not critical, just a preference thing.

Step 15 to 17 as before.
« Last Edit: 05 October 2013, 02:02:50 PM by kebab19 »