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1977 KZ1000 Restomod 13 Mar 2021 09:41 #844861

  • Mikaw
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Skidmark wrote: It's the slow periods that start to get under my skin with mine. For the first time since I started on mine it is under a cover. :( Looking like April at the soonest before I can get back to it. Keep up the progress, I really like where you are going with this bike!


I completely understand. Days go by waiting on a delivery. That will finally arrive and only to realize that what you wanted to do is somehow related to another item that’s out for Plating or I just forgot to order, or hasn’t been detailed yet. The choices are mock it up only to take it back apart later, or wait. The best is to be patient and just wait. The more you “mock” up the better chances are you can scratch or damage something.
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
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1977 KZ1000 Restomod 28 Mar 2021 10:54 #845673

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Getting back into things again. Put the stock forks and swingarm on today to check th height. Raised the frame of the floor and measured from the floor to the centre of the wheel axles. Will make it easier to check if the nose is dipped with the new triples and ZRX forks. One problem though: the shocks that were on the bike don't look stock. Can anybody tell me the length of the stock shocks on the KZ1000A1? Just want to make sure my starting point for the frame angle is stock.
The modified GSX-R swingarm and Öhlins shocks arrived yesterday. I'll be chopping a few things off the frame tomorrow so I can get the swingarm mounted (brake pedal bracket needs to go). Once that's done I can get the ZRX forks back in and check the height of the front and back axles. If I'm lucky the bike will be level at the middle of the height adjustment range on the shocks.

 
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1977 KZ1000 Restomod 28 Mar 2021 14:00 #845682

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Those shocks look a lot like stock '78 Z1R shocks.  Can you post a closer up picture of them?
'78 Z1-R in blue , '78 Z1-R in black, '78 Z1-R in pieces
My dad's '74 Z1
'00 ZRX1100
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1977 KZ1000 Restomod 28 Mar 2021 14:19 #845684

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Looking at some pics and I think you might be right, thanks :)
I will take a couple of photos tomorrow when I'm back in the garage. All I can add at the moment is that they each had two springs - a smaller, tightly wound one at the bottom.

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1977 KZ1000 Restomod 29 Mar 2021 08:58 #845732

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A bit more work done today. Chopped a few unnecessary things of the frame (rusted out pillion footpeg brackets, brake lever brackets seat brackets.

   

 


One of the seat hinges had already been removed - someone was pretty heavy handed with the grinder.

 


Got the GSX-R swingarm and the forks on.

 

 


Checked the axle height against the stock setup. Ground clearance was 130mm/145mm (front/rear) on the stock setup, putting the frame pretty much level when the wheels are on. New clearance is 145mm/80mm. This reduces rake a bit (the two photos below show the difference between stock rake and the new rake (I propped up the swingarm until both axles were at the same height). I can drop the forks down about another 10-20mm, but the major difference is the swingarm and shock length (both are a bit longer than stock). I can shorten the shocks by about 8mm but there isn't much else I can do at the back short of moving the shock mounts.
I realise that the rake will change due to tire profile and sag, the idea here was to get a comparison to the stock setup, not to actually figure out the exact numbers.
I would appreciate some opinions on how this will ride. Do I need to mess around with things, or do I just see how it goes and get a stepped top yoke if it doesn't feel right?

EDIT: Just did some maths and the rake will be reduced by about 3°, so should be about 23°. 

 

 
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1977 KZ1000 Restomod 29 Mar 2021 10:32 #845734

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23 degrees of rake is pretty extreme, most modern sport bikes bikes hover around 24-25 degrees - 4" of trail(102mm). The ZRX1100 has 25 degrees and 104mm trail. The issue with this much rake is when braking the wheel will want to tuck under the bike resulting in chatter. That being said I wouldn't put a lot of credence in this rake number yet since its an estimate. I think you need to take the rake measurement with the bike sitting on on both wheels, the front and rear will sag similar amounts so its not a concern if its weighed down yet. I would also take the time to calculate your trail, and measure the swingarm angle as it looks very steep right now.

FWIW I have ZRX1200 forks on my KZ1000B and to get the numbers I wanted I ended up with about a 1.25" drop triple 38mm offset- with 18" wheels. This left me with 25 degrees and 107mm trail. I wanted to get as close to the ZRX numbers as possible as the valving was designed for that geometry.
 
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1977 KZ1000 Restomod 29 Mar 2021 10:53 #845737

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Do i see a 750/1100 Zephyr rolling chassis and fuel tank in the back ground ?!?!

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1977 KZ1000 Restomod 29 Mar 2021 10:57 #845738

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It seems like the rear shocks are longer?  Do you know the eye-to-eye free length for the new and old?  Since you're already grinding parts off the frame, the obvious choice is to move the frame shock mount forward to lay them down.  Dr. Gamma has some nice pictures of a very fine example, and there have been several discussions.  My impression is that laying the shocks down increases overall wheel travel, and I think it would help to bring the swingarm up closer to the original full-droop position.

kzrider.com/forum/25-racing/614983-81-gpz1100-road-racer
kzrider.com/forum/11-projects/586776-bet...ike?start=336#780625

Of course as DoctoRot said, what really matters is the resting position with the suspension loaded.  Do you know the spring rate and preload for the Ohlins shocks?  The FSM has a graph of position vs load and preload for the stock shocks.  That would allow you to approximate length-under-load for the new and old shocks.

Another thing that factors into the trail calculation is the offset in the triple clamps.  Do you know if the new triple clamps have a similar offset to the original set?
'78 Z1-R in blue , '78 Z1-R in black, '78 Z1-R in pieces
My dad's '74 Z1
'00 ZRX1100
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1977 KZ1000 Restomod 29 Mar 2021 11:02 #845741

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Don't look just at the eye to eye measurements for the shocks. Because the shock mounting point is different on the two swingarms you need to measure from the top shock mount to the axle.  The stock KZ swingarm has the shock mount point quite low in relation the axle compared to most modern swingarms, so you will probably gain an inch or so in ride height there. But ulitimately i wouldn't pay that much attention to this number, what IS important is the swingarm angle. sweet spot is 11-13 degrees. this angle will have a lot of effect on anti-squat and mechanical drive

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Last edit: by DoctoRot.

1977 KZ1000 Restomod 29 Mar 2021 11:14 #845745

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 what IS important is the swingarm angle. sweet spot is 11-13 degrees. this angle will have a lot of effect on anti-squat.
 
I think I asked this before, but I forgot the answer.  :)  Is that 11-13 deg. target for the resting position under load?
'78 Z1-R in blue , '78 Z1-R in black, '78 Z1-R in pieces
My dad's '74 Z1
'00 ZRX1100

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1977 KZ1000 Restomod 29 Mar 2021 11:19 #845746

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11-12.5 unloaded.

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1977 KZ1000 Restomod 29 Mar 2021 12:29 #845752

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Thanks guys, a lot of good info. Sounds like the best thing for me to do is wait till the rims arrive and then get it up on the wheels to see where I'm at. The C-profile that holds the shock mounts is pretty rusty so chopping them and moving the mounts onto the inside of the triangle is an option. This will be a single seater so moving the mounts forward won't be a problem. The mounts need to be moved out about 5-6mm anyway. Is there a range I should stick to for the shock angle?
If I still need to bring the front up a bit I can get the bottom of the top yoke milled out. Can probably get about 20mm doing that. After that it's time to get a new top yoke made... hoping to avoid that (but it would be my own fault for skipping a step in the planning). 

Here's some more info: 
- Shock length: 365mm +8/-2 (thought it was +2/-8... oh well)
- Offset is a lot smaller than stock. Around 40mm +/- (going off pictures, can't find my notes...).

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