FZR600 Front End

1985 RZ350

Modifying the RZ350 Triple Clamps

I have been looking around for a better front end for my RZ350 and settled on a 1990 FZR front end. More modern versions such as the R6 can also be used but the cost of that front end was prohibitive for me so I stuck with a decent bike for it's time and still a good upgrade for the original RZ.

I bought a rolling frame of Craig's List for $250 and set about taking it apart. Everything I didn't need went on eBay to fund the project and netted around $150 so not a bad deal. The riding position will be slightly altered due to the clip ons and I am not sure how to make the ignition key, steering lock and steering stops work, but I'll cross that bridge when I come to it.

After a few hours work I had the bike stripped down to the main frame and wheels. I removed the front end the next evening.

Once I had the FZR in pieces I picked up another RZ350 stem and triple clamps so that my own bike could stay on the road while the transition work was done. Above is the stock RZ350 stem and triples. The idea is to press out the stem from the cast lower triple clamp of the RZ350 and press it in to the lower triple of the FZR. That way the bearings will all work with the RZ because essentially nothing has changed.

The FZR stem is much longer and uses tapered bearings. The only parts I am interested in are the upper and lower trees.

A quick look at the underside of the RZ clamps shows that the stem is not only pressed in place, but also welded. I will take this to a machinist to have them turn down the weld and press out the stem. I made sure I have taken every measurement possible to be sure the stem is inserted in the FZR lower triple with the same length of stem protruding. My measurements on the original show 201mm of stem protruding above the triple clamp.

So the machinist did an excellent job of pressing out the RZ stem and pressing it in to the FZR lower (FZR lower is below the RZ lower above). The machinist commented that the RZ stem was a little wobly in the FZR central hole, and so he built up the inside of the FZR hole with a little weld all around and then machined the hole diameter for exactly the right fit. Also he noted that when removing the FZR stem, it needs to be pushed down from above as it had a small circlip at the bottom side of the triple so that it doesn't get pulled out when the stearing bearings are tightened up.

Another shot shows where he machined off the weld on the RZ lower (below) and then re-welded the RZ stem in to the FZR triples once it was pressed in. Nice job!

The final thing he did was to machine a small collar for where the RZ stem goes in to the FZR triple. On the original RZ triple in the foreground you can see that this collar exists as part of the triple casting, not the stem itself. This collar isn't present in the FZR lower. It is important as this is where the dust seal lies on the RZ set up and without it you won't have anything to ride against the seal and keep the bearings dry.

Above is the roughly assembled front end waiting for brake calipers and controls. The fender is just the old FZR one sprayed with a rattle can to closely match the RZ350 original color.

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