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Author Topic: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)  (Read 24815 times)

Offline hallin222

  • Posts: 163
  • aka: HonkyKong
    • HonkyKong Customs moto-art
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #105 on: Nov 07, 2012, 21:19:34 »
*** FORK LOWERING ***

I've yet to see another KZ750 twin dropped internally like this, and I really wanted to lower my stance to equal to or shorter than those seen in previous pages of this thread, but without the fork tubes protruding past the top triple clamp like done by so many builders (including my inspiration, Wrenchmonkees).

Starting point.  I didn't document the removal of the forks from the frame, becasue if you can't do that, you shouldn't bother attempt the simple procedure below.  I stole this method from the folks over at the XS650 forum.

my source of info:  http://www.xs650chopper.com/2009/06/mulligan-machine-lower-your-xs650-forks-low-buck-garage-tech/



First, drain as much of the oil as possible via the tiny drain screw at the bottom.  Pump the tube to squirt it out.  Warning:  this can make a mess if you're not careful, and it smells awful.

Next, unscrew the top cap via a 1/2 drive ratchet, and remove the main spring.  Mine is the non-progressive one on top.  The other is from a 4 cylinder KZ750 that I thought I might be able to use, but unfortunately, the OD of those coils is about .5mm too large to fit inside my fork tubes, despite the OD of both  bikes' fork tubes being 36mm.



Now came the tough part.  I had  trouble removing the damper rod bolt from the axle side, as the damper just spun, and I didn't have the 'special tool' Kawasaki recommends to hold it still from inside the fork tube.  So, per the instructions from the guys over on the KZ twin board, I cut down what is essentially a broomstick and jammed it in there, while I hit the lower bolt with an air impact to shock it loose.

This is obviously after the damper rod had been removed from the fork leg. 


The contents all laid out in their approximate orientation of assembly.  Not shown is the fork seal, which is still in the casting.


These are the spacers I cut down from some scrap steel tubing.  I've heard of folks using PVC for this, but I feel better about having metal in there.  I don't know why I didn't buy a pipe cutter years ago.  This thing is awesome.  Clean, straight cuts every time.  These spacers will be de-rusted before final assembly.  This was all just a dry mock-up until I can find some 15W fork oil.



Placement of those spacers:



Re-assemble everythig in reverse order, again using the broom stick to allow proper tightening of the lower damper bolt.

Now you're left with a main spring that is a little too long.  Some of this needs to be cut.  As suggested my the XS650 chopper link above, I cut slightly less away from the main spring, as the spacer was long.  Spacer = 1.75".  Spring reduction = 1.5".  This creates a slight increase in spring preload. As a heavier rider, on what I considered to be a very soft set of forks, I thought this would help.  I may add a tiny collar up top to add even more preload but that can wait.



I cut that top section of the main spring with an angle grinder, then ground it as smooth / flat as possible.  The increased preload was not a major change, and I was still able to re-install the top cap with one hand.  Note that I haven't added oil (don't forget that step), but I wanted to show the before & after lengths as seen below.





I still need to perform this on the second fork leg, so full bike photos will have to wait for another day.  These cut springs with added preload feel a tad stiffer than stock, but it's hard to compare without any fork oil.  I'll give my report on that issue when I have some in there.

I hope this helps some foks in the future.

« Last Edit: Nov 09, 2012, 00:00:56 by hallin222 »

Offline crackerman

  • Posts: 300
    • 79' KZ750 builds
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #106 on: Nov 07, 2012, 21:28:48 »
Nice work on that fork chop. I might have to do that on mine. I've rebuilt a couple sets of KZ forks and with out that "special tool" it's a real pain in the ass to pull them apart. I think I ended up doing something similar to what you did but it took me a while.

If your looking for jets for the BS38 carb I just finished jetting my 79kz. Took me a couple of orders to get the right ones but I found them. I'm running pods and Shorty open mufflers similar to what you got. I used a 50 pilot jet(bs30/96) and 135 main jet(n100.606 under pilot jet)Got them from Niche cycle. Def a big improvement over the stock 125, 45 pilot. I know a lot of people don't like the bs38 carbs, but there's not much to them and there easy to pull apart and clean.
« Last Edit: Nov 07, 2012, 21:30:34 by crackerman »

Offline hallin222

  • Posts: 163
  • aka: HonkyKong
    • HonkyKong Customs moto-art
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #107 on: Nov 08, 2012, 00:06:10 »
Thanks, crackerman.  If I don't do the single carb swap, I'll use these as a good starting point.

OK, so I couldn't wait.  I hacked up the other leg and put it all back together dry tonight:



Resting on side stand:


Fully compressed:


Lucky me.  Coil bind (or whatever is causing internal fork 'bottoming') occurs here, and no tire-to-header contact occurs.


This is better:



Offline Cookie

  • Posts: 297
  • God help the child who grows out of everything
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #108 on: Nov 08, 2012, 08:25:32 »
Looking ballin', Hallin! I like that fork lowering
"I fear the day that technology will surpass our human interaction. The world will have a generation of IDIOTS."

GR650 Build thread: http://www.dotheton.com/forum/index.php?topic=49051.0

Offline sinbad85

  • Posts: 329
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #109 on: Nov 08, 2012, 18:27:32 »
great write up on the internal lowering mate!!!

when i had the stock front end on my bike i called three shops nearby to see if they could do this....

they said it wasnt possible..... :o

if i ever go back to stock front end on this ill be sure to follow your instructions......
looks really good!

Offline gk45011

  • Posts: 725
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #110 on: Nov 08, 2012, 19:43:15 »
Lucky me.  Coil bind (or whatever is causing internal fork 'bottoming') occurs here, and no tire-to-header contact occurs.


How much tire expansion do you get with those tires when they are run and heat up? Looks awfully close in the picture.

GK
GK
GS 450L Build thread
http://www.dotheton.com/forum/index.php?topic=39199.0 -SOLD

83 GS1100E = under repair and minor modification

"Cut, shape, grind, repeat. I may not know what I'm doing but I'm enjoying myself." - Rich Ard

Offline Pablo83

  • Posts: 123
  • Sleep, wrench, ride.
    • Catamount Motorcycles
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #111 on: Nov 08, 2012, 23:11:45 »
How much tire expansion do you get with those tires when they are run and heat up? Looks awfully close in the picture.

There was some discussion about this on another site.  I think you're supposed to add something like 3/8" for tire expansion, but more of the expansion is due to centripetal force than heat expansion.  If hallon's ever in a situation where he has the wheel turned this far to the side at highway speeds with the forks fully compressed, he's got a lot more to worry about than melting some rubber to his pipe.
« Last Edit: Nov 08, 2012, 23:17:06 by Pablo83 »
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Offline hallin222

  • Posts: 163
  • aka: HonkyKong
    • HonkyKong Customs moto-art
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #112 on: Nov 09, 2012, 00:03:53 »
if i ever go back to stock front end on this ill be sure to follow your instructions......
If you ever go back to the stock front end, I want your forks.  You know, if you ever visit Texas.

Offline jr0cket

  • Posts: 1
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #113 on: Nov 09, 2012, 00:17:12 »
As always, nice work HonkyKong!  Can't wait 'til mine is a roller and we can knock these both out as "done"!

Offline hallin222

  • Posts: 163
  • aka: HonkyKong
    • HonkyKong Customs moto-art
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #114 on: Nov 10, 2012, 09:02:27 »
I'm reconsidering my lack of front fender. Not for any functional reasons but just because I threw a Burgundy Sportster (or any Harley with a NarrowGlide) front fender on it and I like the shape and even the color.

Fresh_c has suggested I consider an oxblood color somewhere in my paint and although I was thinking more earthtones it could look pretty good.

Offline gk45011

  • Posts: 725
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #115 on: Nov 10, 2012, 16:56:32 »
There was some discussion about this on another site.  I think you're supposed to add something like 3/8" for tire expansion, but more of the expansion is due to centripetal force than heat expansion.  If hallon's ever in a situation where he has the wheel turned this far to the side at highway speeds with the forks fully compressed, he's got a lot more to worry about than melting some rubber to his pipe.

LOL True, you ain't lying there. I was thinking more of tighter parking lot manuvers after a decent length ride.

Diggin the build, looking tits'

GK
GK
GS 450L Build thread
http://www.dotheton.com/forum/index.php?topic=39199.0 -SOLD

83 GS1100E = under repair and minor modification

"Cut, shape, grind, repeat. I may not know what I'm doing but I'm enjoying myself." - Rich Ard

Offline hallin222

  • Posts: 163
  • aka: HonkyKong
    • HonkyKong Customs moto-art
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #116 on: Dec 19, 2012, 12:33:26 »
I was thinking more of tighter parking lot manuvers after a decent length ride.
This tight clearance was only with the forks ratched-strapped down to their fully bottomed out position.  Parking lot manuvers allow several inches of clearance.

Please excuse the lack of updates lately.  I've got a baby boy due any day and preparations have taken priority. I'll get back to this after the new year.

Offline Cookie

  • Posts: 297
  • God help the child who grows out of everything
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #117 on: Dec 19, 2012, 13:22:29 »
That's an acceptable excuse, I suppose.  ;D

Congratulations, Hallin and happy hollidays
...
Happy Hallin-Daze?
 ;D
« Last Edit: Dec 20, 2012, 08:03:43 by Cookie »
"I fear the day that technology will surpass our human interaction. The world will have a generation of IDIOTS."

GR650 Build thread: http://www.dotheton.com/forum/index.php?topic=49051.0

Offline gk45011

  • Posts: 725
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #118 on: Dec 19, 2012, 16:39:15 »
Congrats and Happy Holidays. Best Christmas gift you could ask for!

GK
GK
GS 450L Build thread
http://www.dotheton.com/forum/index.php?topic=39199.0 -SOLD

83 GS1100E = under repair and minor modification

"Cut, shape, grind, repeat. I may not know what I'm doing but I'm enjoying myself." - Rich Ard

Offline hallin222

  • Posts: 163
  • aka: HonkyKong
    • HonkyKong Customs moto-art
Re: Project: "HonkyKong" 1979 KZ750 B Twin (brat-tracker-thingy)
« Reply #119 on: Dec 19, 2012, 17:34:31 »
Thanks, all.  The little free time I've had has been put to making 'art' from my leftover parts pile.  See link in my sig.