front spring tension

[dxtans]

Hello,
I've noticed that the front springs on my d9 are a bit springy when under braking, the seals are good on there. Can the springs/forks be adjusted for a harder setting ? If so how.

thanks for any advice.
dxtans

[Flymo]

Could be wrong but i am under the impression that thicker oil Will slow down the damping, i don't know for the D9 but D6 is supposed to be 10W i'm currently using 15W.

i.e thinner = faster damping quicker compression and rebound), thicker = slower damping (slower compression and rebound).

again i only know about the D6 but extra washers between the fork cap and spring will add more preload, just add 1 or 2 to start with, ii heard rumours that 2p can be used and cheaper than actual washers..

sure there was a thread on here about it somewhere but can i find it ?

HTH

Flymo

P.S not sure bu i think the haynes book of lies has a minimum length for the spring to be useable (i.e within tolerance) maybe someone more D9 orientated could supply that piece of information.

[CD]

My D9 front forks have 15-40 engine oil and are working just fine. I'm sure proper fork oil would be better under race conditions, but for how I use it the fork damping is fine. At ambient temperature the 15-40 is the same viscosity as a straight 15 grade.

The Yamaha service manual (1995 model) says the fork spring service limit is 500mm.

[bobh]

If you do decide to pack the springs up, you'll probably find the max you can get in, and still get the top caps back on, is about 5 mm. Changing to the later adjustable caps might help. But actually all you're doing by packing the existing springs up is getting the forks to work over the same travel but a bit higher up (or a bit more extended if you prefer).

There's a thread about Hagon variable-rate springs somewhere - these have the advantage of beefing the resistance up as you get close to full compression, which sounds like what you're after.

Meanwhile definitely try the thicker oil as a lower-cost option.

[CD]

M & P have a sale on Hagon springs and shocks. I haven't compared them to other suppliers but they do seem reasonable.

[eliminator]

You have played with the adjustment on top of the forks we assume?

[CD]

I have, but cant say I noticed much difference, though I guess it alters the ride height.

[dxtans]

Hello,
Well I also adjusted the setting at the top of the forks, gotta kinda agree with CD, it does not make much of a difference.

I am still getting the springy/juddering under heavy braking ( it ok under normal braking)
I have cleaned the disks thoroughly and the brake pads are good. But still getting the springy feel when braking heavily.
Wondering if I have got a warp disk, the bike has done over 106,000 miles.
Best how to tell though, as I do not have a center stand on it.
Any other idea's on what it could be.

thanks
dxtans

[Padster]

Juddering braking effect can be a sign of steering head bearing wear or adjustment being needed.

[CD]

I'd go with that. I have a slightly warped disc (due to be replaced) but its never caused fork judder. However when I slightly loosened the old steering head bearings (to see how it affected the knotchy steering) the speed weave went away, but there was a definite judder under braking.

If you have engine protector bars, the bike can be jacked up and rested on car axle stands under the engine bars. Then its easy to check the head bearings for knotchiness or slack.

[dxtans]

You could well be right. I've had these replaced before at around 40k mark.
Can I adjust the bearings without taking off the handle bars. If so please advise.

Sorry no crash bars, so in the meantime I'll try and come up with a solution on how to raise the front wheel of the ground without a center stand.

thanks
dxtans

[dxtans]

just thought, I'll balance it on the end of the pavement, get mrs dxtans to hold the handle bars , whilst I give the wheel a pull and push,/twist to see if there is any play.

dxtans.

[CD]

Without a good solid stand there is a good chance of dropping the bike.

Another option is, with some help, to jack up the bike in the garage and tie the frame with a strong rope to a (strong) roof beam, remove the jack and the bike can't fall.

My 900 recently had new head bearings at 48K so there is a very good chance at over 100K they will need doing again.

The steering bearings can be tightened.
Loosend the steering stem nut.
Tighten down the knotched nuts underneath the top yoke/triple clamp
Retighten the steering stem nut.

But the bearings are quite possibly knotchy making the steering heavy and the bike weave at speed. Loose, tight or knotchy steering is an MOT failure.

[dxtans]

well i managed to balance the bike over the pavement, and there is definitely play when the handle bars are held and I twist the wheel.
I 'll have ago at tightening the bearings nut, but I'll probably just book it in for a check and replace if needed.

thanks for the info CD,
dxtans

[CD]

Its better (but not much) to have loose steering bearings than over-tight. The latter can cause a very nasty weave that can suddenly flip into a tank slapper.

M&P were recently advertising paddock stands cheap. With the current market conditions they might have some bargains. I did mine with the centre stand, trolley jack and axle stands, but a proper paddock stand would heve been ideal.

[bobh]

I happen to have a D9 centre stand among the stuff left over from the bike I've been breaking. Took it off yesterday (finally managed to separate the engine and frame) and it seems in good condition, helped by having been covered in oil from a leaky engine. Interested?

When I did my head bearings recently I just put the bike on the centre stand with a pile of bricks on the carrier to bring the front wheel up. I did pack under the engine as well just to be safe, but once you have the front wheel and fork legs off the bike is almost in balance anyway.

One thing that isn't clear from the manual is that the dome nut is effectively the locknut. Although there are the two notched nuts under the top yoke they do not actually lock each other effectively, so I'm not sure why Yamaha bothered with them when one would have done just as well. Anyway, the reason why my bearings went is that the dome nut came loose and allowed the notched nuts to back off, and the hammering effect caused the bearings to "Brinell" and become notchy. So make sure the dome nut is properly torqued up.

[dxtans]

Feb 2, 2009 18:34:50 GMT CD said:

Its better (but not much) to have loose steering bearings than over-tight. The latter can cause a very nasty weave that can suddenly flip into a tank slapper.

M&P were recently advertising paddock stands cheap. With the current market conditions they might have some bargains. I did mine with the centre stand, trolley jack and axle stands, but a proper paddock stand would heve been ideal.

Hello,
Interesting... I initially looked for a paddock stand when I done away with the center stand, could find anything that would do a shaft, even emailing the bike web shops.
Can you point me to the one on M&P please or some other site.

thanks very much
dxtans

[CD]

The shaft swing arm, I'm sure would need some brackets making up.

Its worth having a center stand for these occasions - easy enough to fit and remove without the return spring.

If you decide to go back to centre stand full time. Its well worth welding reinforcing strips 3mm x 25mm steel across at the front and back. Be careful to avoid the return spring's arc of travel. The standard stand is weak and cracks above the weld on the right hand side so these bars really do help. I also powder coated mine. Bargain at £10.