'76 KZ900 (ZRX1200R) Build

Mark,

I have your pics and will post them later.

Leon,

HELP! Lol. I need to know where brace number 4 and number 7 go. Never got those pics.

Cory

Hey! Saw this build on the zrx forum and now over here! Nice!

Like many others, I have a 5/8" offset sprocket and a machined rear hub on my '77 KZ1000 in my avatar. I to have run it w/o a support plate on the street and track days. No issues.

Enjoying your build! Steady on!

I have a '78 KZ1000 that I'm waiting to decide what to do with. I also have a zrx1100 swingarm and soon I'll have zrx1200 KYB shocks and front end. Hmmm. What to do... what to do?!?!

Yes I am trying to keep both threads going at the same time. Lots of pics will be coming lots of welding today! My brother is doing the same build, but using ZRX1100 parts... Good luck making that "difficult" decision on what direction to go! Lol

Cory

All right, lots of pics, so probable will have to break this up. First, things first.

Mark,

Yes it appears it is a 12mm threaded nut. As you can see, it is about .810" deep. It threads onto the stock KZ shock mount per the picture. It is also an allen drive for use.








Bob,

I know you were asking about some dimensional information for the ZRX swing arm. I have both the 1100 and 1200. All dimensions are center to center and in a straight, most direct line.

ZRX1100: Swing Arm Pivot to Lower Shock Mount Bolt: 17.25" / Lower Shock Mount Bolt to the Center of the Essentric locking bolt: 5.50" / Swing Arm Pivot to Upper Shock Mount Bolt: 15.875"

ZRX1200: Swing Arm Pivot to Lower Shock Mount Bolt: 16.75" / Lower Shock Mount Bolt to the Center of the Essentric locking bolt: 6.50" / Swing Arm Pivot to Upper Shock Mount Bolt: 18.25" (on a KZ)

So that should take care of those questions...

Now for the fabrication... I started with welding the upper shock mounts. I tried to match the slope of the stock ZRX, but had to go a little further leaned over due to clearing the factory frame gusset. I made a jig to reference off of the stock KZ shock mount and used a machinist square to ensure it was parallel to the frame tube.





Then started with the lower frame gussets and worked around the bike. The only issue I had with the LH side #7 frame gusset. Pretty sure it will interfere with the seat lock. Next weekend will finish up with installing the oil cooler, steering damper and clearance that gusset if needed.











The finished (for the weekend...) product.


Cory

Great work.

judging by your swing arm measurements , it seem that the zrx12 arm must be a 1/2" longer than the zrx11 ?

as for the spool measurements. 1 pic would have worked. u went over the top.
Thanks very much.

i'mm pretty sure my shock post threads r 12mm. i'll have to check. even so, i should be able to take a 14mm bolt . drill and tap it out to 12mm , then cut it to length and use it as a sleeve. i like the idea of using the spool.
Thanks again.

Mark,

I am an idiot..... Yes it is 12mm not 14. I'll correct my previous post.

Cory

now let just hope that mine is 12 and not 14. lol
thanks.
i'll have to put some of them on my xmas list.

cory,
sorry for the delay buddy :blush: .

looks like you figured out where all the braces went :whistle: , :silly: .

real nice job welding them all in,looks good.

the bike is looking real nice.love the stance :evil: .

keep us posted man.

leon

Leon,

Have you had an issue with the LH side #7 brace blocking where the seat lock comes out from under the seat? I am going to take the latch/lock along next weekend and see if I have to notch the brace.

Cory

Also, one other thing I want some opinions on even though we are not to this part of the build yet. Now, I know I am not a rocket scientist, but i could not get the engine out of the frame without removing the head it seemed. Really this was mainly due to the exhuast studs. That was un expected, but I pulled the head/top side down so i could remove the powertrain and weld the back side of some braces. This engine appears to be super clean on the inside. The thing that surprised me, there is very little appreciable wear on the cylinders? you cannot pick up a cylinder ridge at all with your fingernail on any of the cylinders. this motor had 60K on it when the speedo failed. My question is, how far should I go into the motor? I have not used my snap gauges yet, so I have not checked taper, concentricity, etc... If those are all well within the servicable limit, should I rering it and slap it back together with new seals, possibly valve guides, etc..? Can you get higher compression pistons for a stock bore size? I have built my fair share of hi-po street motors, but this will be my first motorcycle engine build. Thoughts?

Cory

NakedFun wrote: Also, one other thing I want some opinions on even though we are not to this part of the build yet. Now, I know I am not a rocket scientist, but i could not get the engine out of the frame without removing the head it seemed. Really this was mainly due to the exhuast studs. That was un expected, but I pulled the head/top side down so i could remove the powertrain and weld the back side of some braces. This engine appears to be super clean on the inside. The thing that surprised me, there is very little appreciable wear on the cylinders? you cannot pick up a cylinder ridge at all with your fingernail on any of the cylinders. this motor had 60K on it when the speedo failed. My question is, how far should I go into the motor? I have not used my snap gauges yet, so I have not checked taper, concentricity, etc... If those are all well within the servicable limit, should I rering it and slap it back together with new seals, possibly valve guides, etc..? Can you get higher compression pistons for a stock bore size? I have built my fair share of hi-po street motors, but this will be my first motorcycle engine build. Thoughts?

Cory

just remove the exhaust studs and life gets simpler. it can be done with the studs in, but is much easier with them out.
as for the motor. that depends on the type of person u r. some guys,myself included, will want to replace everything, so i dont have to go in there again. others will do the very minimum. we can tell u which parts r known to were and the rest is up to u.
the cheapest piston upgrade, would be a 1075cc kit. u would pick up a good 1015 block and rebore it. u may need to bore the cases to accept the larger sleeves as well. some fit some dont.
i would replace the cam chain($40), and all of the chain rollers($400).
u will hear a debate on whether to weld the crank ($100?)or not. that depends on how hard u will use it. again i am of the do it all school of thought.
this is a deep subject and this will give u something to ponder for now.

since u have a zrx to provide a power ride, i would not recommend powering up the kz. i would build it as a torque type bike, the way it was meant to be.

Mark,

I appreciate the feedback. My SV1000 (piped, air intake, and fuel tuner) is my TQ monster! I get what you are saying, and I plan on changing pretty much all the components (oil pump, timing components, bearings, etc...) anyway, but if I can forego the bore job, to retain as much cylinder thickness as I can, I was thinking about doing it. Will redo the head, and spec out everything (cam lobes, valve stems, etc..) to see if I should replace or not. Since I got screwed on my 28 pumpers, will keep my 26's and pod them, with my exhaust and call it good....unless cams are in my future. So no one makes a non-1015 high compression piston? Even if it is a .5mm over bore?

Cory