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Spring Into Action

Thursday, March 20, 2008

Today is the first day of Spring. Time for a DIY clutch spring workshop. Attention: Eye protection is required!

I have just purchased this new white clutch spring (think it’s a Malossi) from a friend in Seattle whom I’ve met on the AF1racing Aprilia Forum. This new spring is softer than the stock one; and it’s supposed to raise the top speed somewhat, or so they say.

I have been trying to make the scooter go faster without actually dropping in a 70cc big-bore kit (not that I have half-a-grand lying around or busting out of my wallet, either); so I thought that if I mess with the clutch a bit, perhaps it would engage a little faster, which may translate into a slightly higher top end, allowing me to climb the Rainbow Bridge again with more authority, if not a more respectable summiting speed.

Without the aid of an impact wrench this time, I will use a combination of a large rubber hoop-type oil filter wrench plus a socket wrench to dislodge the tough locking nut which holds the clutch assembly together.

First, it’s necessary to hold the rear wheel stationary by tying the rear-brake lever (in this case, the left brake lever) with a zip-tie. Then you place the hoop of the filter wrench over the clutch bell, and the socket wrench to the nut. It’s not an easy task, I will tell you now: but when the socket wrench finally breaks loose the nut, I just can’t tell you how happy I am.

With the clutch bell off, you can inspect its condition inside and out, paying special attention to any abnormal wear or warping. The intense blue and sometimes purple discolorations on the bell is caused by the searing heat generated by the friction from the clutch grinding against the bell and is quite normal.

The clutch is now ready to be disassembled. “Ain’t that a big nut-washer?”; “How am I going to loosen it?”, I think to myself. This calls for some special tools from my toolbox.*

And here are the tools I have. Two pipe wrenches (see configuration). Again, not originally intended for the sort of application; but these pipe wrenches will do the job. (*I have always thought that the best loving thing that a father can pass on to a son is a well-stocked toolbox.)

***WARNING***: To the Uninitiated, after the nut has become loose enough for fingers to turn, it is VERY IMPORTANT not to take it off by loosening it completely! Why? Because the clutch is LOADED; and if you do that, the top part of the clutch may be shooting toward your cute face, under your beautiful chin, or in your mouth before you know it! So, what you do is COMPRESS IT! You can do that by simply place the tip of your foot (I mean shoe) on the edge of the top portion of the clutch, with your hands covering that while applying ample downward pressure, slowly and methodically remove the nut. You will feel the clutch expanding and surging up under your hands and your foot; but since you’re prepared, the moment would not come as a surprise; or worse yet, become an accident, making you a DIY-statistic.

This is the clutch disassembled. You see the top portion of the clutch, turned up-side-down now to reveal the three pads held together by hinges and springs. They’re the elements which actually grind against the clutch bell, eventually locking onto the bell, which in turns allows the plate (see under the spring) to compress against the spring, expanding the clutch and enabling the CVT transmission to “go to a highest gear”. Exactly like a 10-speed bike–largest chain ring in front (in the case of the scooter, the variator compressing) and smallest cog in the rear (the clutch expanding). See video:

Thank you tyfeons for the precisely dramatic “tmax how variator works” video! Excellent!

Enters the new clutch spring, and some visual comparisons:

It’s kinda anticlimactic; but after the stock spring is replaced with new white spring, the reassembling of the clutch and the subsequent re-installation is just the reverse of what you’ve accomplished so far. An important reminder is to first compress the clutch assembly by pushing down on the it with your hands, while holding it down with your (shoed) foot , and then replace the large locking nut. Whew! When it’s all done, go wash your dirty hands and then take a test-ride, paying special attention to any improvement, or otherwise. The way your scooter accelerates, or decelerates will be very different, to say the least. Whether you can live with the new ways your scooter behaves will be another chapter in the ongoing journey of scooter-tuning. Stay tuned.–Lorenzo

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