3TJ Forks. Soft and soggy!

[topfridgeman]

Hello.

I just recently purchased a 3tj 400 running a 94 fzr600 motor. I've taken it for a blast and it seems pretty good now I've had a bit of a play with the rear shock. However, the forks are very very soft. I am 14.5 stone and ride fairly quick. Has anyone got a suggestion as to spring rate or oil to use to cure the droopy front end?

I intend to use the bike for some classic track days.

Sorry if this has been asked before.

Col.

[Evilchicken0]

You can use some heavier oil, standard is 10, but either mix 2 bottles of 10 and 15 to get 12.5 or use 15. You could change the springs, they're reckoned to be a bit light but I'm not sure what weight you'd need.
Moving up the cost scale, you could find some SP forks, they're cartridge type and are adjustable, they don't all have the standard mudguard mounts though.
Lastly you could fit R6 RWU forks, they're 43mm so you can keep the yokes, you'd have to have new spacers for the wheel, and blue spot callipers. The forks are longer than the 3TJ's so you'll need to ditch the mirror brace and mirrors.

[chrisexup]

1999-2002 Yamaha YZF-R6 fork springs are pretty good - they are 0.76kg/mm.
i am currently using 2003-04 Yamaha YZF-R6 springs, which are 0.85kg/mm, i am 12 1/2 stone and haven't managed to bottom these out yet - there's about 20mm of unused travel.
I think i've still got a pair of forks made up from three YAMAHAs which worked quite well - 3tj sliders with fzr1000 exup bottoms, and early R6 springs. These give better braking too - blue/silver/gold spot calipers bolt straight on, and match to bigger 320mm discs (std Yamaha/Ducati/Cagiva/Guzzi/Aprilia fitment bolt straight onto the 3tj wheel). Because you're using the 3tj sliders the overall length is similar too.

[topfridgeman]

So if i go r6 front forks, I can get away with the 3tj front wheel?
I had a quick look into it and the stock axle is 17mm but the r6 one is 22mm?

Have you had any experience with sad usd forks fitted to the fzr400s?
A mate of mine has a set up for grabs. Im happy enough doing the engineering work to fit them if they will work.

Thanks for your advice.

col.

[Evilchicken0]

I think you'd need the R6 front wheel and if so the discs too because the mounting is different. Of course it maybe you can change the bearings and use the R6 spindle.

Take into consideration there's a speed restriction on the 3tj cdi which needs a signal from the speedo which in turn is fed from the front wheel.

[topfridgeman]

I've ordered a set of r6 fork springs and some heavier oil. I'm going to try that before i get too carried away.

All the electrics on my bike are 4jh so there should be no restrictions hopefully.

Col.

[Dcrosby13]

Mine has a set fitted.... I have some spare spacers for sale if you wanted to use the standard R1 top yoke.

[chrisexup]

Col, you might need to make a spacer up from ally or plastic tubing. I can't remember wether i cut down the FZR400 fork spacer, or if i needed to make a longer one .....
i used 89/90 fzr1000 exup fork caps as well, to give me preload adjustment.

[topfridgeman]

Thanks, I will keep my eyes open for a set of 1000 exup fork tops. I had to make a set of fork spacers up as the r6 springs are a good bit shorter. I went out on the bike with just the springs changed last night and it was much better.

I'm going to drop the oil out and change to 15wt oil next. Any idea on capacity per leg or air gaps?

Checked the gearing on my bike too as it seems very high. it had 17/42 on!

Col.

[chrisexup]

standard settings, but as has been said before, this is designed for the jap market and so is pretty soft especially on 20 yr old shocks

fzr 400 rr 509ml of 10wt oil, 80mm from top with fork compressed and spring out

fzr 400 rrsp 433ml of 10wt oil, 106mm from top with fork compressed and spring out

manuals are in the fzr section viewtopic.php?f=35&t=846

I'd try a 100mm airgap with stiffer springs and thicker oil, if there is too much dive on the brakes or you are using too much travel it will be very easy to add a bit more oil until you're happy.
...or start again with 20w oil if you need more rebound damping.