Yamaha C3 – Performance Upgrade

To celebrate my third year riding my 2008 Yamaha C3, I decided to void the rest of the warranty and tune up the performance a bit.  Unfortunately, there’s a very small amount of useful information out there about the C3 (aka Giggle, aka Vox).  I’ve pieced together a good bit of information so I’m recording it here for myself and anyone else in the same position.

The most important thing to initially know about tuning up the C3 is that you must remove the restrictor washer.  Discussions of C3 performance tuning, roller weight modifications, and other changes all assume that you’ve de-restricted the scooter.  If you haven’t, the changes you make will be very confusing and not at all what you are expecting.  For example, I bought a new set of roller weights and had them put in before the restrictor had been removed.  Instead of improving performance, I got great acceleration … right up until 30mph, when the bike hit the rev limiter and wouldn’t go any faster.  Not useful. :)  After removing the restrictor washer, I tested it first with the stock roller weights, and was able to peg the speedometer going slightly downhill with ease – something I had never been able to do before.

The next step is to replace the roller weights as discussed in the movie I linked above.  The roller weights help control how fast the CVT gear ratio shifts.  Lighter weights give you better acceleration and theoretically lower top-end speed, while heavier weights slow the increase in the gear ratio, sacrificing low-end power for higher top speed.  With the C3, one of your more serious problems is slowing down when going uphill, so I believe that, in general, lighter weights are what you want.  This is especially true when you’re using the Dr. Pulley sliding roller weights, which are a different shape that gives you more top-end simply by allowing the plate to move further.

Here’s the information you really need, which took me some doing to find out: the stock roller weights on the C3 are six grams and 15mm x 12mm.  I bought a set of 16×13 4g weights that the shop had to grind down in order for them to fit in the stock variator.  The video I linked above recommends 5g weights, and I think that’s a good recommendation if you’re looking for maximum top-end speed and while retaining some improved hill-climbing performance.  My current Dr. Pulley weights are probably around 3.9g after being shaved down, and while low-end acceleration is good, high-end is somewhat lacking.  I can’t measure top-end speed at the moment as the speedometer is not useful past 40mph. My opinion on this may change after some experimentation, I’ve only ridden a few miles with the shaved 4g weights.  Also note that while the stock roller weights may not entirely wear out, after 12,000 miles mine showed serious signs of uneven wear with several weights having multiple areas that had been rubbed flat.

Finally, your tires are important.  I replaced the stock C3 tires with Michelin Reggae tires (the stock tire on the Zuma) after the stock tires wore out.  This turned out to be something of a problem – I lost 3-4mph on the top end, going from being able to hit 42-43 to being stuck around 39mph (this was before de-restricting and replacing the roller weights).  I believe that the Reggaes have a significantly higher rolling resistance, which accounts for the slower acceleration and lower top speed.  Finding tires with lower rolling resistance turns out to be another difficult problem, as many tire manufacturers don’t list the rolling resistance of the tires they sell.  This is my current line of research, and will probably end in calling the tire companies and trying to get the information directly.

One final note – working on the CVT on the C3 is trivial, as even I can do it.  Once you get the hang of it, the whole thing only takes about 10 minutes to take apart.  You need:

• A strap wrench big enough to hold the variator in place while you get the variator bolt off (see the video)
• 10mm, 8mm, and 17mm sockets and a socket wrench with an extender that’s at least four inches
• 5mm Allen wrench (hex wrench) to remove the kick starter

The hardest part is getting the variator bolt off – I had to use a length of PVC pipe to give myself enough leverage to get that 17mm bolt off, and it took me a few minutes to get the strap wrench set properly to allow that leverage to be used.

My next step will be to order a set of 5g 15×12 Dr. Pulley weights and compare those to the shaved 4g ones I have in there now.  After that, I should have the tire research finished and a new set of tires on order.  With those upgrades in place, I should be close to 50mph as my top speed while retaining the C3′s 115mpg fuel economy.  Then, maybe, I’ll look into a new pipe.

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