FZR600 Front End

1985 RZ350

Installing the FZR600 Forks

Now that the RZ forks are completely free and the old bearing races have been removed, the FZR600 fork can be installed. There are two main hurdles that need to happen: 1. The steering stops on the FZR lower triple are not the same as the RZ triple, and the steering lock will no longer function due to a much lower ignition switch location.

The first step is to mount the upper and lower tapered bearings which I bought through Spec II. I wish I had written down the model numbers but I installed them before doing this.

I found the easiest way to fit the lower race was to place it in the bottom of the frame steering tube and use the previous bearing race as a hammering surface to gently tap it in to place.

Both races should face so that the bearing diameter closest to the triple is larger. I tapped equally at 0, 90, 180 & 270 degrees of the old race so that it went in squarely. The same situation worked well for the top too.

Now that the races are in I installed the dust seal on the modified FZR triple with an RZ stem, followed by the lower tapered bearing.

At this point I installed the triple without any grease and followed it at the top with the upper tapered bearing, collar washer, and finally the stem nut just finger tight. I used the same ignition switch from the RZ which is a perfect fit and then installed the upper triple and tightened the upper stem bolt finger tight to see how the steering stops and steering lock would work.

Well - neither one worked. It turns out that my RZ frame stop was a little bent presumably from a crash from a previous owner. Even if it wasn't bent the stops would have been off. I found it turned to the right so much so that the upper triple touched the tank, and to the left so that the triple stopped about an inch from the tank. I actually temporarily fitted the fork tubes for this test to make sure the lower and upper triples worked together.

To resolve the steering stop I measured an inch from the tank when turning to the right which worked out to be about 1/4" of material that would need to be added to the left hand side of the frame stop. My welding isn't great but I figured this didn't have to look pretty. I used some scrap metal and got it down to the size I needed with a bench grinder then clamped it in place with Vise-Grips. In a perfect world I would remove the bearing races but I was using a MIG welder which goes from nothing to "hot" immediately. I did very small tack welds to hold the piece in place and cooled the metal with a sponge in between. As far as I can tell there is no damage to the new bearing race, and I was only welding to a tab off the steering stem, not the stem itself.

The next issue was making the steering lock work properly. The RZ's ignition key is mounted much higher on the upper triple than the FZR so even though the ignition switch fit well, when the lock pin was extended it didn't catch anything. I took some initial measurements, found some old 2x2x1/8" steel tube and cut one side off to make a tab. I then turned the upper triple to my one inch from the tank mark, moved it back a hair, and noted where I would need to weld the tab. I disassembled the forks and got to welding. I was able to use the existing tab and simply add to it as shown. Works like a charm.

Above is a finished shot at the modifications with the steering stop smoothed and ground down and both tabs painted black to match the frame. Again, not the prettiest work, but it will do its job and it really won't be seen once the headlight is in place.

With these two items complete I was able to remove the triple and stem, grease the bearings, and do the final assembly. The RZ system doesn't use a locking nut on the stem nut, but basically sandwiches it under the upper triple. I haven't ever found any specific information about how tight to tighten the main nut. If it is too tight the bike will weave , if it is too loose the front forks will shudder under braking.

Basically I did it finger tight and then used a C-spanner to turn it another 1/2 turn. We'll see what results I get when the bike is back on the road. Follow the main nut with the upper triple and stem nut, but only install it finger tight until the fork tubes are placed.

The fork tubes can now be installed from below. Each one will need to pass through the lower triple and then through the upper triple with enough space protruding from the triple to allow the clip on to be installed. You can loosely fit them both remembering to install a crate under the fork ends when finished just in case the bike tries to tip of its main stand.

I found the easiest way to get everything aligned was to temporarily fit the front axle finger tight, and then install the two clip ons so each is perfectly flush with the top of the fork tube. Then let gravity pull the clamps down until the little pin in the triple aligns the clip on correctly and its lower face lies on the triple clamp face.

From here you can tighten the two upper triple clamps, and then tighten the main stem nut as tight as you can. Once this is complete, tighten the lower triple clamps and the forks are now officially in the RZ frame.

Fit the FZR600 front mudguard and fork brace and tighten the bolts down from the under side.

Remove the temporary wheel axle, fit the speedo drive hub to the front wheel, and then install the wheel with the speedo drive hub to the driver's left of the bike. Make sure the speedo drive recess slots in to the forks properly so that the hub doesn't rotate with the wheel. Grease the main axle and push it through the hub and tighten it down once it threads into the other side.

Finally and very importantly fit the pinch hex key bolt which stops the front axle from loosening over time. Be very sure to fit this and double check it as it replaces the older system of a locknut and cotter pin.

With the clamps in place, I simply slid on the re-used RZ350 switch gear and grips all except for my reconditioned FZR600 master cylinder. As far as I can tell the clutch perch is exactly the same on both bikes. The bar end weights are different on the FZR and I plan to use some with built in mirrors. I find when splitting lanes the area that gets the tightest is stem mounted traditional mirrors and the side mirrors of taller SUVs.

More to come soon....

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