1977 KZ1000 Restomod

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Just remembered my problem with replacing the top yoke: the clip-ons will break my back

ha i hear that, what forks are you using again to the exact model and year?


 

They're ZRX1100 forks. Not sure on the exact year but as far as I know all the ZRX1100 forks are the same.

I was on webike and age ago and i thought i saw fork extensions for the zrx but its for the ohlins forks.
www.japan-webike.ie/products/20945727.html
 

Im fairly sure and decent machinist would be able to grasp the concept, these guys illustrate it fairly well and you are only looking for 40 mm max right? it might work out cheaper and you would get to keep those real nice top yokes.

www.extremecreations.com.au/kawasaki-fork-extensions

Thanks! That was what I was thinking of, I was just missing the extension of the fork upper. With that added the tube overlap will stay the same. Should be pretty easy to make, just need someone to cut the threads on the top extension (don't have any M30 taps or dies lying around). Then of course the million dollar question - will the German MOT guys want some paperwork...

calum post=847887Thanks! That was what I was thinking of, I was just missing the extension of the fork upper. With that added the tube overlap will stay the same. Should be pretty easy to make, just need someone to cut the threads on the top extension (don't have any M30 taps or dies lying around). Then of course the million dollar question - will the German MOT guys want some paperwork...

What if you keep the extension 2 0r 3mm less than the thickness of the top clamp, will they even see that they have been extended that way? wow Germany has some strict ass rules, there is nothing like that here in Ireland. you could superglue your bike together and no one would care except the morgue or the organ droner clinic.

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What if you keep the extension 2 0r 3mm less than the thickness of the top clamp, will they even see that they have been extended that way? wow Germany has some strict ass rules, there is nothing like that here in Ireland. you could superglue your bike together and no one would care except the morgue or the organ droner clinic.

Yeah, it is a bit nuts over here. It seems that things used to be a bit like back home - if you knew the right guy... But the right guy seems to be harder and harder to find.
I did think about the fact that I only need 30-35mm and the triples are 40mm. Might just get away with it

I've been through this a couple of times before, I had the tubes on a set of 43mm GSXR forks extended, don't forget you'll need to extend the damper rod and spacers for  the springs as well. 
I'm using a 45mm set of showa's from a 2001 speed triple on my 750 R1, I bought 100mm longer fork tubes for this project, then made up a 100mm screw in section for my damper rod and alloy tube spacers for the springs, It was a bit of work but turned out great.... This pic is similar to what I had made up for the GSXR forks.

 

I spoke the the guy in the link KZ streetfighter posted,  last year, he was only doing extensions for USD forks...

Thanks. I've been thinking about extending the ZRX damper rod and am not sure it will be easy. The compression(?) settings are down that end of the fork and do something with the end cap for the damper rod. I think I'm going to have to pull them apart and see what's in there.

Yes, pulling them apart is the way to go, you'll understand everything when you see what's inside. Both of the sets of forks I modified were adjustable for spring preload at the top, to retain that I had to extend the damper rod.... To extend the damper rod I used a piece of small alloy tube, I cut my damper rod, threaded both ends, then cut thread into the tube to the desired depth, Put loctite on everything and screwed them all back together, it was pretty easy and worked very well. 

Just as a matter of interest, here's a good read on suspension setting up..

www.triumphrat.net/threads/suspension-setup-step-by-step.30391/
 

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Spent a while measuring things today and realised I made some mistakes on the calculations yesterday. Here's what I tried today:

Standard setup (forks flush with top yoke, rear axle in the middle of the chain adjument range): 

• Rake: 22.5°
• Trail: 89mm
• Swingarm angle: 11.3°

Forks dropped (forks sunk 10mm into top yoke, rear axle in the middle of the chain adjument range): 

• Rake: 23°
• Trail: 92mm
• Swingarm angle: 11.6°

Lowered back end (forks flush with top yoke, rear wheel raised 35mm towards frame): 

• Rake: 24.5°
• Trail: 100mm
• Swingarm angle: 8°

 

I think you should try a combination of several things
1. internally extend forks - 12- 20 mm I'm not sure but i think you can extend them a little without needing the top caps.
2. Mill bottom of top triple clamp. 15-20mm That sucker is way over engineered. You could cut it in half and it would be OK
3. Lower rearend till swingarm is at 10 degrees. 

Other things to consider:
Shorter swingarm? New swingarm is much longer than stock which means to achieve desired angle you need the rear end to be relatively higher.
Low profile rear tire
High profile front tire.

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I think you should try a combination of several things
1. internally extend forks - 12- 20 mm I'm not sure but i think you can extend them a little without needing the top caps.
2. Mill bottom of top triple clamp. 15-20mm That sucker is way over engineered. You could cut it in half and it would be OK
3. Lower rearend till swingarm is at 10 degrees. 

Other things to consider:
Shorter swingarm? New swingarm is much longer than stock which means to achieve desired angle you need the rear end to be relatively higher.
Low profile rear tire
High profile front tire.

I sorted out point 2 today - it was more of a question of MOT paperwork. Milling out 15 mm leaving about 15 mm around the top bolt. Not going right across the bottom, just a 60mm circle around the bearing cap and nut. Will then cut a M28 x 1 thread in the stem and use a nut instead of the top bolt - will be easier than shortening the stem. This change will put me at around 23°/95mm rake/trail.

Point 1 is now on the backburner until I get the forks apart and see what is required. I'm pretty sure I can't just put a spacer at the bottom and use a longer damper bolt as the compression settings will get messed up (I think...). I think I'll look at adding about 15mm to the top of the damper rod [EDIT: that won't work ]. As you said, there should still be enough overlap between the uppers and lowers when fully extended.

I can shorten the shocks a bit (gets the swingarm to about 10.5°) but I probably won't bother moving the shock mounts to bring it up any more. May consider the mounts that scrirocco posted a while back just to lay them down a bit.

The wheelbase is at 151cm so may offset the steep front end - or it may just make things worse
Basically, once I've had the top yoke milled and decided what to do with the forks I think I'll just get the bike together and see how it rides (before I pull it apart again and paint it). If it's dodgy once I get it on the road I'll look at moving the shock mounts and/or putting a Zephyr swingarm on it. 

Thanks for the suggestions! I'm really hoping the changes at the front will get me where I need to be.

The wheelbase is at 151cm so may offset the steep front end 

Unfortunately it doesn't work like that, its all about balance between the two, lengthening the swingarm a little can be beneficial to handling, but too long and the rear is wanting to react slower to turn in while the steeper front wants to turn faster. these older Kawasaki's have been developed for racing for well over 40 years, there's plenty of info online and I've posted some here, don't guess, do some research, you'll find the information you're looking for...

This is again from sanctuary's site for their 18 inch wheel bikes, it can read a bit weird due to translation    "Since the caster angle is set to 24.5 ° to 25 °, which does not deviate significantly from the normal, in most cases a stem with a fork offset value of 45 mm is used. If you want to secure the steering angle of the steering wheel, which is an important factor on the street stage, in the practical range, I think that the offset value of 45 mm is the minimum necessary."     They use a swingarm length of 500-510mm measured from the centre of the swingarm pivot bolt to the centre of the axle at its most forward position, this is also using  front suspension length of 790mm to 800mm . 
So in summary, rake 24.5 to 25 degrees  , swingarm length 500mm to 510mm, and front fork length 790mm to 800mm. and they've used a 45mm triple clamp offset

18 inch wheel sanctuary bike with these dimensions
 

Thanks for that, some really good info there.

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don't guess, do some research, you'll find the information you're looking for...
 

It's less guessing and more trying to get the most out of what turned out to be less than ideal advice. Not really bad advice, just less informed than I assumed - and we all know what assumption is the mother of I should have posted more questions about the chassis here as I did with the engine 

More numbers:
I went back to the garage and adjusted the rear axle as far forward as it would go - 520mm pivot to axle.
Offset is 40mm
Forks are 770 (according to the internet, haven't actually checked)

My forks will end up sitting at a point about flush with the top yoke on the Sanctuary bike you posted - giving me about the same height as a 790mm fork on that bike (plus a bit more due to shorter offset).
I lifted the front about 14-15mm off the ground today to simulate lengthening the forks. Put me at about 24.5° (rough measurement, will do some trig later). Swingarm was at 11° and the shocks would sit about where the silver cross is in the picture below (pretty close to the sanctuary bike and where pretty much everyone else seems to put them). This would put the shocks at about 28° to vertical, as apposed to 18° with the stock mounts.
Lengthening the forks by 15mm and moving the shocks should sort things out. Wheelbase will be pretty close to the sanctuary numbers you posted (10mm longer swingarm, 5mm less offset), albeit with both axles about 5-10mm closer to the rear of the bike. Rake will be at 24-25° and trail will be a few mm longer due to the shorter offset. Should be a pretty good starting point though (still have room to move with fork height in the triples and adjustable shock length).

@DoctoRot: do you have any numbers for the ZRX rear suspension/geometry? The shocks are for a ZRX so I'd like to base things off that, couldn't find any numbers though.