CBX '79 With Kawasaki ZX-9R & Yamaha FZR1000 suspension

[bikeymikey748]

SUPER impressive! You’re work is outstanding.
Thanks for sharing with us. Eagerly watching all the new posts.

[AshishNJ]

What a beautiful build. Keep pictures coming please

[RC 166]

Thanks bikeymikey748 and AshishNJ !

This must be one of the longest sleeping projects on the forum. I bought my first red CBX '79 in 2000 and that one I have been riding every year since then (I sold that one in 2022).
Some months later, in 2001, I bought this one and decided to only test drive it a few months and then build it as a special. I bought a lot of different parts for trial, measuring etc. before I in 2007 locked my radar on the parts I use now. The project has been on and off due to work in CNC shop, work on houses, other stuff, but in 2023 I started to work continuously.


Mounting the footpegs:

OK, this day I thought I could just mount my footpeg plates "Euro Sport Kit" as you call them. Did they fit? Nope! Well the left side did, but not the right side. Problem was the enormous brake lever, designed for a baby to stop a truck. The lever on the inside of the plate that pushes the main cylinder is too bulky.

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Lyckily I had a set from a Suzuki GSX-R 1100 '92 kicking around. I made a simple mock-up bracket to test fit them and they seemed to fit the CBX perfectly. Don't know how comfy they are yet though. The peg gets approx. 65 mm further back than stock when mounted in the frontmost bracket holes, same hight as stock. I made some "real" brackets so I could fit the Suzuki set. This only solves the pegs for the driver. I will make a solution for the pillion pegs too, don' know how yet. Either new custom "Sport Kit" plates or an add on bracket to these. I have it in the CAD at the moment.

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I didn't like the round hard pegs that came on the Suzuki set, so I modified some CBX pegs I had laying around.
On the brake side I tried the fat driver's peg and on the other side I tried the skinny pillion peg. It was a no brainer, I went for the fat driver's ones.
Everything will of course be cleaned and polished prior to final assembly. No black paint etc...

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[RC 166]

Just mention that I also have a project-in-the-project adapting the Denso alternator mechanically to the CBX engine.

It's over here
viewtopic.php?f=21&t=12535

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[oroepke]

Impressive build! Looking forward to seeing the finished machine!

[NobleHops]

I just 'socialized" this thread on the Club Facebook page, so more visitors are likely inbound. This is some of the best tech and eye candy we've had since Mike(eybikey) built his amazing custom a few years back. Thank you so much for taking us along on this project!

[Syscrush]

I just 'socialized" this thread on the Club Facebook page, so more visitors are likely inbound. This is some of the best tech and eye candy we've had since Mike(eybikey) built his amazing custom a few years back. Thank you so much for taking us along on this project!

I'm a bit ashamed to be part of the crew referred here from FB. I've gotta get back to being a more regular reader and contributor here!

Can't wait to see how this works out for you.

The custom parts you've made look amazing - especially the work on the drop-down top yoke. It seems like you've thought everything through, I'm curious about what you're thinking/planning regarding the bike's suspension geometry. How will the front and rear ride height compare to stock given the changes you've made? Have you calculated how the donor bottom triple will affect the trail?

For what it's worth, on my bike my choice of swingarm and shock lifted the rear almost an inch, which took out about 1° of rake. I also increased the offset of the triples vs OEM, so I ended up with the trail reduced by almost 10mm. The result is geometry that's closer to something like a CB550 or Bandit 1200 - and with the Superbike bend LSL fatbar I am really, really happy with how it turns in. It's not like a real sport bike, but in transitions it's similar to a Monster 1100.

[RC 166]

Thanks oroepke, NobleHops, Syscrush for the kind words!

Syscrush,

I am not near my CAD computer right now, but I measured a lot and drew everything in very detailed CAD-files, both OEM CBX and CBX Special geometry. I will open the files when back at office on monday and return with answers.

Anyway, I know that the ZX-9R Triple tree offset is 35mm vs OEM 47mm which oddly results in a 115mm trail vs OEM trail of 120mm.
How come it's shorter with a smaller offset?
-The smaller 17" wheels drops the front axle 30mm.
-The rear wheel tire diameter is 25mm larger than the front wheel's, which lessens the rake by 0.5 *.

I have measured the wheelbase of the assembled special chassis and it is 1515mm when the wheels are off ground and rear wheel at front stop in the swing arm.


Can someone tell if the official OEM wheel base 1495mm is when the wheels are off ground and rear wheel at front stop in the swing arm?


I also use a Renthal style "fatbar", 28mm in the clamps tapered down to 22mm at control ends.

[Syscrush]

It sounds to me like a very nice setup that will work as good as it looks.

In principle, the lower ride height means less cornering clearance, but IMO it's not a good idea to push to that limit on public roads anyhow. I wanted to keep stock ride height or higher, but I know that's just my dumb hangup. My conservative riding style on the street means I could give up a LOT of lean angle and never know.

I don't have hard data for this, but I also think that modern and properly tuned suspension will buck back and forth less than the OEM stuff (especially after 40+ years of wear), which would make the actual dynamic ride height on a bike like yours closer to stock than the static #s would indicate.

Again - nice work, I look forward to seeing more updates.

[RC 166]

OK, I have checked my CAD-files and notes from OEM vs Special chassis.

I compare ride hight at two points.
1=center of top shock mount bolt to ground with complete bike on the ground.
2=top of top yoke to ground with complete bike on the ground.

1. The Special is only 6mm lower than OEM. (Special's shock mounts are taller and "gives back" 19mm ride height).
2. The Special is 19mm lower than OEM.

Difference between 1 and 2 is 13mm. The distance between 1 and 2 is 965mm which gives 0.8 degrees nose drop (rake decrease).
I wanted nose drop rather than rear drop as a goal and can drop even more by lowering the triple tree.

The ground clearance will only be 10-20mm less than OEM, and I can live with that since I don't drive that aggressive.

Wheel base and trail for the Special is 1512mm vs 115mm.

My shocks are NOS Ohlins HO 153's from ca '94, c/c=364mm, stroke=97mm, spring preload=17mm (the only adjustable feature aside from different springs of course).

Yes, I think also that it will buck less given that I now have needle bearings instead of plastic bushings in the swing arm. For starters, that is....

[Syscrush]

From my own experience, I think you're on exactly the right track - assuming you get those forks sprung and valved appropriately. I'm looking forward to seeing more.

[RC 166]

Hi,
I just started a new thread, "Footrest Plates & Footrests" viewtopic.php?f=102&t=12693
because I think there is room for improvements to my ideas here sofar. I want to simplify more by not using rear set on brackets etc...

[RC 166]

I have done some research on the front brakes on the ZX-9R '98/'99 front end.They come with Tokico 6-pot calipers.

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Unfortunately, the Toks are more or less crap due to poor quality ( not anodized piston bores/seal grooves). Thus you have to strip them for cleaning frequently. And they are also a nightmare to bleed. The ZX-9R community have found the Nissin 4-pot calipers with 90mm bolt spacing from Suzuki GSX-R's, Bandits and Triumph's from the 90's much more effective. "It's like night and day", reliable braking power all the time, less disc drag, easier to bleed. Well, belive my luck when I found 4-pot Nissins with 90mm bolt spacing in excellent shape (<34 000 km) on my GSX-R 1100 '92 front end that I had "kicking around".

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As the ZX-9R front end is not designed for the Nissin calipers you need to pay attention to the choice of brake pads. Buy pads for Thriumphs (EBC FA 236 HH) instead of the GSX-R 1100 version (EBC FA 145 HH)! The Thriumph pads have same backing plate dimensions, but the sinter material gives a better footprint on the ZX-9R disc. I have made a simple rig to verify that. It is a see-through partial "ZX-9R disc" that exactly shows what is going on in there.

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The FA 145 HH pad interferes with the disc bobbins!

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[RC 166]

I have disassembled my Nissin 4-pot calipers (from a Suzuki GSX-1100 R '92) and started to refurbish them.

I must say, what quality! No corrosion what so ever after all these years. have to admit though, that I bought these around 2003 and they have been sitting in tempered rooms since then. But anyway, and how does the Tokico 6-pots look after 30+ years?

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[Larry Zimmer]

Superb!! Engineering at its best.