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FZ600 Swingarm
FZ600 Swingarm
1985 RZ350
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Measuring & Installing the Offset Sprocket
This page assumes you already have the FZ600 rear end in the bike and the rear wheel mounted. Since the rear sprocket carrier will now be out of line with the original front sprocket it is important to get a measurement of how far out of alignment they are in order to get the offset correct.
The first step is to make sure the wheels are aligned with each other. Since the rear wheel adjustments basically push the wheel to the left or to the right, it is important to make sure that both sprockets are parallel to each other.
The basic idea is explained here, but it involves using two strings with weights at the front wheel end and measuring the distance to the front tire when the string just touches the side of the rear tire.
In practice I found an 8' level was a much better way of determining when I was parallel with the rear wheel, especially with a brand new tire. I balanced the level on some cans and could easily determine when it was touching both the front and rear edges of the rear tires, and then measure the distance to the front and rear edges of the front tire.
Once the wheels were aligned, I carefully clamped s amll extruded tube on the outside face of the rear sprocket. The picture above shows it on the inside face because I forgot to take a picture on the outisde, so be sure to use the same face of each sprocket in your measurements. Also be sure to clamp the tubes just tight enough to hold it in position but not any tighter.
I then did the same thing with the original front sprocket.....
I was then able to get the two tubes to cross over and I could measure the difference between the ends which worked out to be 7.8mm. I double checked this figure by adding all the widths of the various rear wheel components together of the original RZ and the new milled down set up and agreed witihn 0.2mm so it is good enough for me.
The problem was that the suppliers I talked to only make offsets front sprockets in 1/8" increments. 1/4" was too little, and 3/8" was too much. I noticed when I removed the original sprocket there is a collar that rides against the oil seal, and I realized that I could get the 3/8" (which is 9.5mm) sprocket and machine down the collar by 1.7mm instead to get to my desired measurement.
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