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Tech Tips from Racers for Racers
Dear Pocket Bikers,
How do I properly set up the clutch?
This is a how-to article on proper Bi-Zeta clutch setup and maintenance.
When you first get your new Bi-Zeta clutch, you need to properly set it up for maximum use, and longevity. Before your clutch is installed on the motor, you need to adjust it. These procedures are the same regardless of the model of Bi-Zeta clutch.
The first thing that needs to be checked is the spring height. This is done by measuring the distance between the top of the washer and the upper edge of the backing plate (SEE PICTURE). Riders should invest in a good set of calipers for precise measurement, or borrow them from a fellow racer. This distance should be set to 25mm exactly, or as close as humanly possible.
After the 25mm spring height adjustment has been attained, you need to measure the total height of the clutch, it should fall right about 78mm. This step is important, so pay attention.
IT IS IMPORTANT THAT THE DISTANCE BETWEEN THE OUTER EDGE OF THE CLUTCH PAD MATERIAL AND THE INNER EDGE OF THE DRUM IS WITHIN 1 – 1.75mm FOR EACH PAD.
A 25mm height gives an initial stall speed at about 8,000 rpm. This is about ideal. However, for those that like higher stall speeds, listen up. ZOCCHI DOES NOT RECOMMEND ANY HIGHER THAN 8,900 rpm, his personal dyno-testing proves that it is not effective for the powerband, or good for the clutch. 8,600 rpm would be the upper effective end of the range.
Now plop the newly adjusted clutch in your clutch drum and housing, and measure the distance between the inner edge of the drum and the outer edge of the pads. If they are right about 1 – 1.25mm, then you are right on target. Now, you are ready to install the clutch.
PLEASE READ STEP 5. IF YOU ARE PLANNING ON USING THE CARBON FIBER CLUTCHES FROM BI-ZETA.
Install the clutch on the motor, tighten it down, put on the clutch housing, start the motor, and check the rpm with a digital tach. If you are satisfied, and the clutch feels like it is kicking you in the arse, then your job is done. If you want to go 100 – 200 rpm higher, then just turn the adjusting nuts with a 7mm wrench, and recheck the rpm. You are done and ready to ride.
Some of you have expressed concern that the carbon fiber models aren’t holding up to the stresses of racing. I broached this issue with Zocchi, and he says that a properly adjusted clutch should last a long time regardless of the size of the rider.
However, Zocchi also noted an oversight, which has been corrected, and future clutches after August will have new features. The problem with the CF models was that the clutch pad material thickness was only 3mm versus the 4mm of the standard Bi-Zeta material. What does this mean?
Well, a properly adjusted 25mm clutch will fall out of tolerance by 2mm total, and thus not properly engage with the drum, thus slippage. If the rider fiddles with the spring height to make up the difference, then it was worsening the situation, because the springs weren’t being properly compressed and basically ineffective for use.
Correction: in future CF clutches, and replacement CF clutch pad kits. Bi-Zeta is providing a spacer (SHOWN IN PICTURE) that will be 1mm thick to make up the difference in the height. This will allow a user to properly set up the 25mm height and enjoy the long life of the CF clutch.
This picture shows where the new spacer will go on new clutches after Aug/September...
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