Team modifications

UPDATED 01-11-02

Rear End

● The standard oil in the rear shock absorber is too thick (8000 wt), replace with 6000wt or 7000wt

● There is a small rebound spring Inside the rear damper unit under the piston which is too weak. Consider replacing this spring with a stronger item. At normal ride height this spring should not be doing anything but should come into play the moment the rear starts to jack itself up under acceleration.

Front End

Since its introduction the NF501 has come with a various different steering control systems. Having tried both (spring & Silicon tubing) we can say that neither method has a significant advantage over the other. However the silicon is easyer to install with the springs easier to adjust when fitted

This is our current preferred setup

Please note that in standard trim i.e with no front disk brake the servo mount and servo have to be rotated 180' to allow for different lengths of steering linkage. Also make sure that if you use the silicon tube method the tubing must be 'pinched' tight between the two collets to stop the tube sliding along the steering link.

Ian's Wobble categories (sometimes referred to as steering oscillation)

There are three types of oscillation that we are experiencing with these bikes.

Grade 1

This is the gentle swaying from side to side normally present when slowing or accelerating out of a corner. This is accentuated by running the fork legs too loose (often donw to prevent the fork legs from binding). Also brought about by the use of a steering damper that is too stiff.

Grade 2

This is the shimmy that the front end has over ripples or under hard acceleration. Its kind of like the bike rides straight and true but the front wheel has very violent wiggles from left to right. It is these that the steering damper cures.

Grade 3

Lastly there is the wild tank slapper where the whole bike has a wiggle and interestingly the steering damper makes this worse...........now were learning something.

Consequently I think we need the damper as light as possible so that oscillation grade 2 although still present is controllable but so that oscillation grade 3 never happens or if it does damps out quickly.

Rider figure

The rider figure is one of the most important tuning aids in as much as there is a fair degree of weight and it is high up on the bike, which has the effect of raising the C of G (centre of gravity). Treat the tank/seat/rider as one unit, make sure the rider is securely attached as any movement however small upsets the balance of the bike. A weight of 85 gms for the complete tank/seat/rider unit is hard to achieve but a good target weight. Don’t detract from the aesthetics of it though. (It can be done)

Understanding Steering geometry

Making it turn...

Keeping it simple, the less the angle of rake the more the bike wll turn. I.e screwing the rake adjuster screw down and bringing the forks closer to vertical.

However this has two unuasual and contradictory side effects. On one hand it increases the effective front wheel castor or offset, which increases the straight-line stability. However, I doubt that you will ever notice this as it also reduces the front wheel trail which makes the steering itself less stable, and the bike has a much greater tendency to oscillate. Primarly cat 2 wobbles get progresively worse under acceleration.

Solution. Just starting..... Run the maximum ammount of rake that you can and still keep everything off the ground. As the rake is increased it is normal for the fairing to hit the ground before the side guards. Either run less rake or extend your forks by 5mm to overcome this.

As you get better run progressively less and less rake up to the point at which the cat 2 wobbles get too much

Cat 1 and cat 3 wobbles are related. A cat 3 wobble is just a cat 1 that gets out of hand.

The steering damper only really helps with cat 2 wobbles (see Ian's tests) so I think most of the time it wants to be off or only very minimal.

The steering damper transfers the wobble to the frame which in turn passes it to the only other point of contact, - the rear tyre, which we already know has its own problems.

Generally, on rough tracks or fast tracks just run a lot of rake, its so much easier to ride

On smaller tracks it may be better to just jump in with a "low rake angle set up" but be prepared to tighten up your steering system (more preload on the steering springs or shorter silicon) but be prepared to have more wobbles. Note some of these arnt worth trying to cure its better to learn to live with them.

Bounce off of the side guards when entering a corner is drastically reduced with the steering damper off as well. It makes a BIG DIFFERENCE

The bounce off the side guards that you may have noticed when riding your bike is not a result of the stiffness of the material just the position of the point of contact. To reduce the bounce run longer side guards but angle them upwards. This places their contact patch further away from the tyre contact patch and reduces bounce.

Other stuff

The front brake can be run either as intended (trailing) or as shown in the pictures of Ians bike as a leading caliper. The trailing method gives a smoother and more progressive brake action but ultimately you can get better braking forces running it as a leading calliper. The smoother cable run transfers more power and the design of the brake encourages the pads to dig in.

Here is a good view of Ian's bike showing various Team modifications. The first obvious one is the lump of red silicon tubing around the crash back spring. This is here because the spring is just too weak and we noticed during one of our tests that under harsh acceleration the front wheel would 'bounce' backwards and forwards against the crashback. This bit of silicon stiffens it just enough to stop this but still allow a degree of protection against front end collisions. While we are on the subject of collisions you'll notice the heavy re-enforcement to the inside of the fairing. Another thing you'll notice in the picture is Ian's neat servo installation. Opting to ditch the bracket that comes with the front brake kit because it raises the C of G too much. Ian has managed to sandwich the receiver between the two servo's and the whole lot sits snuggly between the two halves of the frame attached by servo tape. The big blob of blu-tak is just to keep water out of the receiver.

The picture clearly shows Ian's method of attaching the silicone tubing. Rather than pushing the tubing on the end of the servo horn, Ian has screwed a self tapping screw vertically into the horn and then pushed the tubing onto the screw with a small cable tie for extra security