wrote:

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.

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:
 

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.

He has not logged on to KZR since January 2019.

Myke?

wrote:

My eyes keep going back to the Suzuki!  I had an '83 GS750E that I put almost 60k miles on.  Can you spill some info (without going too far off the topic).

Sure skidmark,
   1983 GS11es with some "period correct" upgrades. Astralite wheels, Fox Shox, Sandy Kosman rotors, Spondon calipers, Metmachex swingarm, 35mm Keihin CR Special carbs, Motogpwerks exhaust and RaceTech GSXR11 forks recently added

 

wrote:

wrote:

Hi Ed, I know from reading previous posts of yours you don't think they are needed, yes the 650 is very stable, I have fitted dampers to every bike I've owned that didn't come stock with them. Have you ever had a tank slapper ?   I have, one bad enough to dent my tank with my thumb, broke the steering lock tab on a 750 Honda back in the early 1980's at speed, frightened the poop out of me, have used them ever since, Think of them as an insurance policy...

  Besides this is my sons first bike, just being over cautious...




 

I asked because some folks believe they are a cure for speed wobbles even though the speed wobbles may be an indication of a serious problem that needs to be addressed.  My 1977 KZ650 developed bad speed wobbles several years back.  The problem ended up being bad Michelin Macadam tires.  I found the problem after replacing the swing arm bushings, steering stem bearings, shocks, etc., etc. Replacing all those items slightly dampened the problem, but replacing the tires made the problem absolutely go away at any speed.   It appears that the bike in question does not have any wobble so the damper is not being installed to try to correct an existing problem; that's good.  That's why I asked.  Ed

     I get where you're coming from Ed. The 650 has new stem bearings, wheel bearings, brakes, it uses my 750R1 forks that were completely rebuilt just before I bought it, {pulled them down to check them and found everything perfect}, which was a pleasant surprise, new rear brakes and all set up almost right, I need a little more preload in the front forks but apart from that, it rides and stops very well, actually I'm impressed just how well these 650's handle. I'm definitely not trying to hide any handling gremlins....

wrote:

Hi Ed, I know from reading previous posts of yours you don't think they are needed, yes the 650 is very stable, I have fitted dampers to every bike I've owned that didn't come stock with them. Have you ever had a tank slapper ?   I have, one bad enough to dent my tank with my thumb, broke the steering lock tab on a 750 Honda back in the early 1980's at speed, frightened the poop out of me, have used them ever since, Think of them as an insurance policy...

  Besides this is my sons first bike, just being over cautious...



 

I asked because some folks believe they are a cure for speed wobbles even though the speed wobbles may be an indication of a serious problem that needs to be addressed.  My 1977 KZ650 developed bad speed wobbles several years back.  The problem ended up being bad Michelin Macadam tires.  I found the problem after replacing the swing arm bushings, steering stem bearings, shocks, etc., etc. Replacing all those items slightly dampened the problem, but replacing the tires made the problem absolutely go away at any speed.   It appears that the bike in question does not have any wobble so the damper is not being installed to try to correct an existing problem; that's good.  That's why I asked.  Ed

wrote:

This is the jig i made for shock mount location.
Adjustable for stock or custom positions, different swingarms, width etc and has drill guide and location pin attachments .
Also good for checking the stock shock mount positions which are hardly ever exact.

Thanks zed - looks like that would make things a lot easier. Any chance you could post a few more photos? I can see what looks like two adjustment screws but I'm not sure how everything fits together (how the two sides are kept aligned, how the shock length is locked into place...).

Took some measurments today.
The GSX-R swingarm has the same spacing from the pivot bolt to the lower shock mounts as the stock swingarm. The axle is 30mm further down and 55mm further back with respect to the bottom shock mount. The new shocks are 20mm longer.
I'll wait until the rims get here but the plan at the moment is to move the top shock mounts to the same location as the Z1000J. After that I'll see if I need to drop the top yoke down or not.

Put a few things together today so I can see how the riding position is when the footrests get here. Would be interested in opinions on whether I should go with scantily clad or fully naked: