Soggy FZR600 forks

**kerryg** · 3rd August 2004, 12:33

My 1989 FZR600 has a pretty crude front suspension. No adjustment possible and it is very soft (I can nearly bottom the forks by pushing down hard on the bars). I've done a bit of research and apparently the factory springs are rated at only 0.464kg/mm while Race Tech's $300 springs for the same bike come at 0.89kg/mm for my (not inconsiderable) weight. I'm a bit reluctant to fork out $300 on such an old bike so has anyone got any advice about modifying the existing forks? I could put heavier fork oil in (standard is 10 weight, so could go to 15 or 20) and I could put a spacer in to increase the pre-load, and even shorten the factory spring (my research indicates a shorter spring is a stiffer spring) BUT will this give me the result I need? I don't want something completely "wooden" or a pogo stick result at the front any more than the current marshmallow situation, and I wonder whether anyone has any experience of this kind of exercise?

**James Deuce** · 3rd August 2004, 12:47

Originally Posted by kerryg

My 1989 FZR600 has a pretty crude front suspension. No adjustment possible and it is very soft (I can nearly bottom the forks by pushing down hard on the bars). I've done a bit of research and apparently the factory springs are rated at only 0.464kg/mm while Race Tech's $300 springs for the same bike come at 0.89kg/mm for my (not inconsiderable) weight. I'm a bit reluctant to fork out $300 on such an old bike so has anyone got any advice about modifying the existing forks? I could put heavier fork oil in (standard is 10 weight, so could go to 15 or 20) and I could put a spacer in to increase the pre-load, and even shorten the factory spring (my research indicates a shorter spring is a stiffer spring) BUT will this give me the result I need? I don't want something completely "wooden" or a pogo stick result at the front any more than the current marshmallow situation, and I wonder whether anyone has any experience of this kind of exercise?

Preload doesn't stiffen your springs it just starts suspension travel further up or down the range according to the adjustment you make. Heavier fork oil adjusts the damper rate on how quickly the oil flows through various damper holes. The new springs, combined with heavier fork oil would get the result you are after. My TRX suffered from soft, harsh suspension and the Racetech fork springs have made a HUGE difference. It is well worth it in my opinion, and you wouldn't know yourself once you've done it, even on such an "old" bike.

**kerryg** · 3rd August 2004, 12:53

Originally Posted by Jim2

The new springs, combined with heavier fork oil would get the result you are after. .

Thanks for the reply, Jackrat. What weight oil did you go to?

**James Deuce** · 3rd August 2004, 12:59

Originally Posted by kerryg

Thanks for the reply, Jackrat. What weight oil did you go to?

Me Jim2, me not Jackrat.

I went for 15 wt in the end.

**riffer** · 3rd August 2004, 13:08

Here's another idea.

The FZR600 will accept the FZR750 or FZR1000 front end. You need the forks, triples, and clip-ons. You can take everything from the 87 model through till they went USD, I think in 93.

Reason you need new clip-ons is that the FZR is about 39mm tubes. The 87-88 models are 41mm, and its 43 from 89 on.

Of course, you need to be able to find some. Try Aussie. There aren't any in New Zealand. I know, I've tried.

My bike runs a full FZR1000 front end. Quite firm, especially with 20wt oil in it.

What you might want to try is the springs out of some FZR1000 forks. Try the wreckers. There are a few crashed FZR1000's around with rooted forks, but the springs are still quite usable. That may work too.

**wkid_one** · 3rd August 2004, 13:20

Mate - Call Suspension Tech in Ellerslie ( http://www.suspensiontech.com/ and ask him what he thinks. He did the front end of the VTR and it made a wicked improvement to the bike - esp given the VTR is similar to the FZR with hellishly undersprung forks (VTR spring rate is ideal for someone weighing 56kg according to Race Tech's man and website).

I would go with new springs. Anything you do to the front end of the FZR like changing oil, spacing for preload etc is only going to minimise the problem and is never going to erradicate (like that word?) it. Adjusting preload won't help bottoming out, and changing fork oil won't either.

Go for the new springs. Try sourcing them from different places or buying OS yourself - and then I dare say you will be able to find someone on here to help you fit them if you can't yourself.

$300 is a small investment in the handling of the bike.

Either than - or buy a new one.

**geoffm** · 3rd August 2004, 13:27

Fizzer forks are pretty budget.
Cheep fix is 12.5wt (50% 10wt and 50% 15) or play around to suit (you may need 15 if you are porky), and reduce the airgap. Off the top of my head I can't remember the airgap in the fors we ran in the 400. Don't go to overboard, as you will lock up the forks

Increasing the oil weight increases the compression (and rebound) damping, and you may find the forks become harsh adn don't react to a series of bumps - just skips off the top if you go to heavy.
The airgap acts as a rising rate spring, and reducing this increases the effective spring rate. Again, don't go silly otherwise you may as well weld the top and bottom together, and you will pop the fork seals (always weak on these anyway).
For a guess, reduce the airgap by 20mm and try it.
What is the static sag - adjust this with the preload spacers.
Geoff

**kerryg** · 3rd August 2004, 14:02

Originally Posted by Jim2

Me Jim2, me not Jackrat.

I went for 15 wt in the end.

Sorry about the name mix-up Jim and thanks for the info

**kerryg** · 3rd August 2004, 14:04

Originally Posted by geoffm

Fizzer forks are pretty budget.
Cheep fix is 12.5wt (50% 10wt and 50% 15) or play around to suit (you may need 15 if you are porky), and reduce the airgap. Off the top of my head I can't remember the airgap in the fors we ran in the 400. Don't go to overboard, as you will lock up the forks

Well thanks Geoff I think

**kerryg** · 3rd August 2004, 14:11

Originally Posted by wkid_one

Go for the new springs. Try sourcing them from different places or buying OS yourself - and then I dare say you will be able to find someone on here to help you fit them if you can't yourself.

$300 is a small investment in the handling of the bike.

Either than - or buy a new one.

Yes I think I will, and thanks for info. I'll see what I can pick up on EBay. Even retail in the USA they're under USD100 so why you have to pay NZD300 (just under USD200) in NZ beats me

**riffer** · 3rd August 2004, 15:11

Originally Posted by kerryg

Yes I think I will, and thanks for info. I'll see what I can pick up on EBay. Even retail in the USA they're under USD100 so why you have to pay NZD300 (just under USD200) in NZ beats me

Shipping costs. They are horrendous...

**wkid_one** · 3rd August 2004, 15:26

Originally Posted by celticno6

Shipping costs. They are horrendous...

No man - get it from the UK as the shipping costs are HEAPS betta. I don't buy out of the States as the price of the goods are great - but the shipping can often be more than the goods.

Last time I paid five pound postage to NZ and it arrived in 2 weeks. Total purchase price was only $70NZ - it was quite heavy too as it was footpegs and titanium sliders.

Try these sites for springs

http://www.mandp.co.uk/homepage.aspx...uct&arg=527245
They have Hagon, Progressive and Ohlins Springs
Progressive Springs are UK$59(So NZ $140ish)

http://www.racinglines.co.uk/html/suspension.html

http://www.biketorqueracing.co.uk/Ha...orksprings.asp
About UK$72 per pair

http://www.hagon-shocks.co.uk/Fork_Springs.htm

FZR600 GENESIS

88-93

500-065-04

10

150

That is the part number, recommended SAE and Air Gap (in mm, fully compressed, springs not fitted)

More links if you need them - go to this site......

http://www.bikersweb.co.uk/directory...ccessories.htm lists all the bike shops in the UK

**FROSTY:Me** · 3rd August 2004, 15:40

I had an 89 fzr600 and had the same problem. I spent ages stuffing around and finally bit the bullet and bought a set of Progressive brand fork springs.
I used 15w oil and used 20cc more oil than factory reccomended.
It totally transformed the front end of the bike.
The progressive springs were from memory like $150 nz
Oh and I wnt down the path of spring spacers and it was a total waste of time.
Dang ya gotta love log books .

**kerryg** · 3rd August 2004, 16:48

Originally Posted by XJ/FROSTY

I had an 89 fzr600 and had the same problem. I spent ages stuffing around and finally bit the bullet and bought a set of Progressive brand fork springs.
I used 15w oil and used 20cc more oil than factory reccomended.
It totally transformed the front end of the bike.
The progressive springs were from memory like $150 nz
Oh and I wnt down the path of spring spacers and it was a total waste of time.
Dang ya gotta love log books .

Thanks Frosty that's helpful.