VFR400 NC30 geometry

[Bud977]

I am rebuilding an NC30 race bike, and have noticed that the chassis geometry is unusual. The front end rake is nearly 28°, whereas the published standard is around 25°.

The bike is fitted with a 17" RVF back wheel, a modified stock rear shock, and later model forks with modified springs, spacers and Chinese tubes, linkage unknown.The 17" tyre is only 5mm smaller in radius than the 18" wheel I have, so that makes bugger all difference.

I can drop the front by 20mm by sliding the fork tubes through to help with the rake, but really the back end needs raising.

Can someone measure the height of the swingarm pivot from the ground so that I have a reference point to work towards? Mine is at 370mm with both wheels on the ground.

At the same time could you measure the distance from the bottom of the bottom triple clamp to the front axle. Mine is at 480mm with the forks fully extended. The static sag is 10mm which is not enough. I need to cut down the spacers as the preload adjustment is wound right off.

The shock is close to topped out with the current preload and actually needs turning down, so I can't use the preload to raise the rear.

How much difference in does an RVF linkage make to the ride height?

Is it possible I installed the linkage back-to-front when re-assembling the rear suspension? Is it reversible?

Ah, so many questions. I hope someone can help.

[CMSMJ1]

is the hub installed the right way up?


stick a pic up..

[Bud977]

That was quick! Good thinking. I just double checked the hub and it is right. The axle is in about the 7-8 o'clock position (hard to tell exactly but it's toward the front and bottom).

What can I send you a pic of?

[CMSMJ1]

just how slack it is - something is not right.

the chinese tubes - are they the right length?

[Bud977]

After reading about the problems with the Chinese tubes, I measured these ones up before fitting them.

The tubes are 6mm longer and the seat for the top out spring is 11mm higher up. This results in 11mm less travel and 5mm more preload. No a big deal. The overall length of the assembled fork is 680mm from the top of the fork tube to the axle centreline. What is standard?

With this set-up, I've got 2mm of tube poking out of the top triple clamp. I can have 24mm poking out before the fork sliders hit the bottom triple clamp.

I can take some pics tomorrow and post them up.

[Neosophist]

After reading about the problems with the Chinese tubes, I measured these ones up before fitting them.

The tubes are 6mm longer and the seat for the top out spring is 11mm higher up. This results in 11mm less travel and 5mm more preload. No a big deal. The overall length of the assembled fork is 680mm from the top of the fork tube to the axle centreline. What is standard?

With this set-up, I've got 2mm of tube poking out of the top triple clamp. I can have 24mm poking out before the fork sliders hit the bottom triple clamp.

I can take some pics tomorrow and post them up.

Odd one.

Its late and im mega sleepy but all I can say is that K model (only compression forks) or L model (two way adjustable forks) if you use the stock tubes and have the snap ring on them to set the fork height in the yokes then they both sit at the same height one the bike (I have both sets of forks have have swapped them both and checked them)

[Bud977]

The Chinese tubes don't have provision for the snap ring. Instead of using the snapring for a reference, I had to work it out myself. The Haynes manual doesn't list a protrusion for the standard fork.

You must be somewhere in my timezone. It was pretty late when I wrote my post as well. zzzzzzz.......

[Bud977]

I thought the K model had no adjustment, and the K,L,M had damping adjustment. That's what the manual says anyway.

[CMSMJ1]

I thought the K model had no adjustment, and the K,L,M had damping adjustment. That's what the manual says anyway.

You are right, Neo was tired

K model has preload only, no damping.
the others have damping but it is a combined adjuster - it alters both circuits.

[Bud977]

If someone could measure up the swingarm pivot height, with the shock fully extended, that would be great.