Early fireblade rwu forks into a z650?

[dixiethedog]

I know I should go buy some alloy and make some new yokes,but im being lazy. Ive been doing some swopping of parts with a friend and have inherited a RWU set of Fireblade forks (no bottom yoke)and a one off billet top yoke.
I recall reading somewhere that the correct yoke offset for an early zed is about 43mm? The fireblade ones are a lot less. Apart from the possible reduction in turning circle,what negative effects will the new front end have regarding handling? I never understand all this tech talk about rake and trail,as im stoopid. Has anybody used this front end already on one of their bikes???

[KWACKERZ1]

Brett,
I think that standard z900 yokes are 68 mm offset and z650 yokes are 43mm offset.
Modern stuff tends to be less Zrx32mm and blade96 16" front wheel is 35mm.

Generally this will make the thing turn quicker but can affect the stability in a straight line and also have a tendency to drop in quickly when you turn the bike.

http://bikearama.com/theory/motorcycle- ... explained/

[dixiethedog]

Thats what I thought.
I was reading on a project thread that somebody building a very nce bike had Harris measure up the dimensions for some yokes that came out at 43mm offset.
I might just have to give them a try,and if its crap,machine some new yokes.
Thank you for your advice.

[LondonZ1]

Brett
The Z900 has a standard offset of 60mm and a trail of about 97mm. It's the trail that matters, not the offset as it's the trail that affects the stability of the bike. If you fit a smaller front wheel then the trail will reduce which in theory makes the bike less stable. The solution is to reduce the offset, which then increases the trail. The maths are actually fairly simple, I ended up producing a simple spreadsheet to check the calcs. You also need to watch out for fork length as you will need longer forks with a smaller wheel if you don't want to lose ride height.
When I was designing my suspension, my goal was to keep the trail and ride height roughly standard and make sure that if it did sit a little lower, then the reduction was the same at both ends. That way the bike still sits level and you haven't messed with the geometry too much.
Trail sounds complex but it's just the distance between the tyre contact patch and where the steering stem axis intersects with the ground. Too little trail and it steers like a supermarket trolley.
Hope this helps!

[jimmock]

What about using the 'Blade RWU forks as originally planned, but......



Fit a 22 inch front wheel.

This would slow the steering up somewhat and increase straight line stability.

[KWACKERZ1]

Brett,
I have just fitted z650 yokes 43mm offset to a 1000 of mine I'll let you know how well they work.

Harris magnum geometry is based on a 45mm offset yokes 29 1/2" forks and an 18" diameter wheel Lester Harris told me that and said that Magnum 's will still be slow steering compared to modern stuff.

So give it a try and see how it feels, as there are plenty of zeds running round with gsxr forks and yokes and 17" wheels.

[dixiethedog]

I supplied a kawasaki USD front end to my good pal,who's building an 1100(gpz)engined z650. I'll have a ride on that soon and see how it feels.
The blade forks Ive just put my hands on have no bottom yoke yet,but a billet one off top yoke. Ive a big (by home workshop standards)milling machine,so might have a bit play when i have some spare time.
Ive plans to paint the fork bottoms candy gold fork legs with the bottoms silver,with billet polished caliper carriers. Possibly with radial brakes too. Id like it to look a lot more expensive than it really cost.