'76 KZ900 (ZRX1200R) Build

full time engineer eh :whistle: ?

well i am sure we can come to some sort of agreement there sir.

leon

Especially if you like a certain brand of diesel engines..... I used to do special race application stuff for turbochargers as well....

Cory

Your Build looks very cool, apart from the very slick pivot bolt arrangement did you have to modify the ZRX swingarm at all or did it fit well into the frame? Also what is the dimension from top of forks to axle center of your new forks, I presume they too are from the ZRX?

I like the original colour scheme if that is what you will be doing.

Bluezbike

What type of diesel engines do you work with? What did you do with the turbochargers? Design bigger turbos? Will you explain what all went into getting the front end all switched. Did you have to switch trees? Did they bolt right up? If so what are you doing about the guages? And what about the speedo? does it still have a cable that will still screw into the guage?

To answer the previous questions:

1. Yes, the stock ZRX swing arm had to be modified slightly. If you read the post from above, I explained by front and rear what needed to happen to install them. The swing arm pivot tube (which is aluminum) that all the swing arm bearings reside in, needed to have the right hand side trimmed about 1/8" of an inch. Due to KZ frame tolerance, this dimension could vary slightly.

2. The front required the stock KZ stem be swapped by machining a reducer bushing that adapted the OD of the KZ steering stem to the ID of the ZRX original steering stem hole. In addition, the top ZRX triple had to have its steering stem hole enlarged from 18mm to 28mm to fit the top of the KZ steering stem.

3. I have not measured the length of the ZRX forks from axle center point to the top of the fork. I can try and get that information for you if you want. All suspension, wheels, tires, brakes came from the 2001-2005 ZRX1200Rs. The ZRX still used a 160mph speedo driven by cable. they are 43 mm forks that are fully adjustable and rebuildable.

4. I am using stock gauges for this build. I like the vintage look, but will be moddified visually to fit the theme of the bike.

5. I work for Cummins. I do own a 7.3 Powerstroke (T444E) though. I used to spec out and build custom turbos for applications that Holset (the turbo manufacturer) did not make stock. Anything from Subaru powered airplanes to 700ci Aries alcohol pulling tractors.

I think that was all the questions? :woohoo:

Cory

It would be awsome to work for cummins. And your bike looks great. Iam wanting to change my rims to a newer style i will probally go with a busa rear and gsxr front. I heard it dont take much to get a gsxr rim to fit the front.

great job so far. a few things that may come up.
u can take the 2 speedo cables apart (kz/zrx)and make 1, as the ends r dif for each bike at the bottom. i ended up doing that, then i switched to zrx gauges as well.
u will need to grind off the lower footpeg boss on the inside of the frame for chain clearance.
i had to flatten the inner frame for chain clearance as well. i also run a rooller under the chain to keep it off the zrx arm.
if u lay the shock down forwards at the top, it will ride better. it will ride stiff like that, unless u r very heavy.
hope this is helpfull.

Mark,

You are running a 5/8" offset though right? I am running a narrower 3/8" offset and milling the rear hub to slide the rear sprocket toward the centerline of the bike. I have considered leaning the rear shocks forward, but I am 260 lbs and I can change the rear spring rate with different springs if required. I am also measuring the geometry against my ZRX to see how far I am off a stock ZRX geometry. As far as the peg bosses go, I am not sure how I haven't decided what direction to go with the pegs yet. I may weld in new peg mounts for my rearsets, or make adapter plates that mount off the stock peg bolts, then mount to my rear sets. It is still in flux. I know you have been down this road before, so your expertise is always appreciated.

Cory

Hi Cory,

My question about the length of the forks is because I will be building a bike up this winter and I am gathering as much information as I can before I start as I have never done this before.
I followed a discussion earlier in another thread about how important it was to know exactly what one is doing when changing out front ends which in turn can alter the way bike handles, sometimes very badly, not a situation I want to find myself in. Length of forks was a biggie as well as offsets, trail etc. Many thanks for all the replies.

Alec aka Bluezbike

Alec,

No problem. I will take those measurements tonight and post them up.

Cory

NakedFun wrote: Mark,

You are running a 5/8" offset though right? I am running a narrower 3/8" offset and milling the rear hub to slide the rear sprocket toward the centerline of the bike. I have considered leaning the rear shocks forward, but I am 260 lbs and I can change the rear spring rate with different springs if required. I am also measuring the geometry against my ZRX to see how far I am off a stock ZRX geometry. As far as the peg bosses go, I am not sure how I haven't decided what direction to go with the pegs yet. I may weld in new peg mounts for my rearsets, or make adapter plates that mount off the stock peg bolts, then mount to my rear sets. It is still in flux. I know you have been down this road before, so your expertise is always appreciated.

Cory

i am running a 5/8 offset, and i too milled the rear hub. i ended up running a 170 tire. at 260lbs u may be fine. i found that my 170 lb ass kept getting bucked off the seat on the stock shock mounts, so i copied the zrx geometry . it rides much smoother now.
As far as the peg bosses go, i meant the lower one on the inside of the frame. it stick out a bit and the chain hits it with a 5/8" offset.

Yeah I may do that, but I thought instead of altering the lever arm advantage, I would simply just change to a lower spring rate altogether. According to RACETECH, a ZRX with my weight should have a 3.5 kg/mm spring rate instead of the 2.7 kg/mm stock rate. This is figured with the factory ZRX shock angle and a wet weight of 492lbs. The KZ I think is 525lb stock ( would have to reweigh after build is complete) with a steeper shock angle might be appropriate. Need to look at this a little more...

cory