1977 KZ1000 Restomod

Had a bit of time today and got the wheels on. Checked rake and trail and without changing anything I'm at 22°and 94mm. I crunched the numbers and if I can raise the back by 7-8mm I'll end up with 25° and about 107mm trail. Slightly more trail than the ZRX but I have 10mm of adjustment in the shocks. At the moment I can go about 3mm shorter and 7mm longer so I'll probably centre them and lift the back wheel by about 7mm. Then I should have a decent range of adjustment in both directions. I haven't checked the swingarm angle yet (a job for tomorrow) but it looks a bit steep so lifting it up a bit should be fine.

 

  

  

I'm a little confused by your post Calum, you say your at 22 degrees and 94 mm, then if you raise the rear you'll be at 25 degrees ?   If you raise the rear while you have 22 degrees you'll end up with LESS rake and trail....  I posted this earlier in your thread   "Geometry measurements also depend on what size, diameter wheels are used, usually a slightly steeper steering head angle and less offset for  17 inch wheels , for example, AC Sanctuary use 23.5 to 24 degrees of rake and 40mm triple tree offset with 17 inch wheels,"

Probably not worded too well - seems to be a recurring thing with me
By raise the rear I actually meant raise the swingarm with respect to the frame. I'm thinking of where to put the axles to get the geometry right instead of thinking about the position of the frame. So yeah, I meant lower the frame (or raise the rear tire when the bike is on the stands).
I'm aiming for about 100-110mm trail. Everything else is just getting set to what I need to get about that value (the adjustment in the shocks will be enough to change things up if needed. I have a 40mm offset but stuck with 18" wheels - that gives me about 107mm trail @ 25°.
I waited until the wheels arrived before taking any measurements so I could be sure of the numbers. I am just going to set eveything up with the suspension unloaded - if I set the static sag correctly the trail won't change with the engine etc. in the frame.

EDIT: The plan tomorrow is to raise the front end on the stand until I have the numbers I want, then to see how far off the ground the front tire is (the rear is just touching). Then I can see where the shock mounts need to be to get the rear tire level with the front.

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°

All this means that I can't lower the back end or my swingarm will be too flat - makes it easier to deal with the shocks, don't need to move the mounts anymore. My only option is to raise the front end. Here's what I've though of so far, suggestions are more than welcome:

• Put a spacer in between the fork damper and the fork lower to lengthen the fork. Not sure how much I could gain with this before I start to lose stability in the forks, maybe 15-20mm and chuck a fork stabilisor on?
• Find some 43mm fork uppers that are longer than the ZRX's. No idea where to look though...
• Drop the forks in the top yoke - can get about 9mm out of this before going past the top clamp bolt. Would need some covers for the tops of the forks though - it looks pretty sh**. 
• Get new triples with a 30mm drop - really don't want to do this  
• I can probably get about 5-10mm if I play around with static sag once the bike is assembled.

Any other ideas?


Forks dropped in the top yoke:
 

Rear end lowered so the rake/trail is good - swingarm is too flat:
 

Would it be beyond you budget to have a set of top clamps made and sell on the ones you have? with a fabricated drop like the ones i had made here? Or machining out the bottom of the top clamp to allow the clamp to drop further like i did in the second pic. the only other solution i can see is a fork extension kit and if you find one it might be same cost as a new top clamp...

Maybe you could ask your friends at RF-Biketech what it would cost to make a custom top clamp.  A top clamp seems simpler than those wheels they made.  At 30mm of drop you may have tank interference issues, but maybe you could also incorporate the clip-on mounts into the top clamp?

I did think about machining out the bottom of the top yoke, but it would mean either putting a spacer over the stem or shortening the stem (which will cause problems with the MOT over here as the paperwork is then invalid). I could only really get about 10-15mm with this so I'd still be a bit short.
Getting a top yoke with a drop is a good option, but I wasn't sure if I'd need a drop on the bottom as well (to keep the clamping distance the same and ensure stability). Just not sure what effect reducing the clamping distance by 30-35mm will have on stability - I assume not much but it may be problematic to get the paperwork. I'll check up on it.

What's the drop on your top yoke (bottom of the centre section to top of the fork clamps)?

wrote:

Maybe you could ask your friends at RF-Biketech what it would cost to make a custom top clamp.  A top clamp seems simpler than those wheels they made.  At 30mm of drop you may have tank interference issues, but maybe you could also incorporate the clip-on mounts into the top clamp?

They made the triples I have now and they do a triple clamp with a drop (on both yokes). Not sure if they'd do a drop on just the top yoke - it depends on what they have the MOT paperwork for. I'll check with them tomorrow.

I have checked and JMP make a 43mm fork upper that's 647mm long. If the top thread is the same as the ZRX I may be able to just swap out the tubes...

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

EDIT: DOHC - I just reread your post and I'd missed the bit about integrating the clip-on mounts. A good idea but the only time I've seen this there was no way to adjust the angle.

wrote:

What's the drop on your top yoke (bottom of the centre section to top of the fork clamps)?

15mm mate.
and the gain i got from the recess on the bottom was 10mm.
 

wrote:

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?
 

wrote:

wrote:

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.