Yamaha C3: Unexpected results from what I thought wasn't an ecomod.
 

Since I got my Yamaha C3, (Just a little 49cc bike :turtle: ) I've loved it since I got it, but I've always felt it would be nice if it had just a little more power, particularly up hills. I enquired at a local scooter place every 6 months or so until recently they got a part in that they said would help.

It was some sort of set of rollers or something (little round wheeley things) that were supposed to help out. The first thing I noticed was that they were oddly shaped - instead of being round, they were about 3/4 circles, with a sort of soft triangle that sticks out on the remaining 1/4. Definitely not circle-looking.

So, it turns out that the effects were somewhat different from what I expected, yet good in an entirely different way. Here's what it's like to drive now:

At the bottom end, from 0-20mph I have quite a bit more torque, and also rev noticeably higher. This is good for situations where I'm starting from a stop going up a steep hill, or when I just plain old feel like accelerating quickly.

Now around 20-25mph, something kinda weird happens - the scooter feels as though it's shifting gears. Now for those of you not familiar with the C3, it's got a Continuously Variable Transmission, which means, well, it shouldn't shift. Now, I gather that the weird shape of the rollers that were installed has something to do with this, probably causing some kind of change to do with the way the CVT is varying the gear ratio. Effectively, it's just like shifting.

Past 25mph, the engine revs a LOT lower than it used to, this has a few effects that would be expected of such a change: First, though my acceleration uphill is better until about 20-25, it, well...really sucks after that. Second, my top speed has gone up from 37mph to 43/44mph, quite a significant change. (I have no idea what it is since my speedometer stops counting at 60km/hr which is about 37mph and I can bury it now). Third, even with my "enjoying" the new top end of the scooter, I've gotten the best mileage tank yet, about 114mpg. (My previous best was 110.8mpg, and that was in much better weather - my last tank with the current weather was about 105mpg). Now, of course it's possible that there's a hiccup or something with my mileage, so I'll have to see how the next tank works out. I'm thinking that if I take it a little easier on the speed, I can probably get even better mileage.

If there are any other C3 owners this interests, I'll check what the part was for you. I'm not exactly Mr. Technical, if you couldn't tell.

Maybe I should start cardboard modding this thing. Kinda sounds like fun to me.

CAD (Cardboard Aided Design) streamline the thing and make it go 65 :thumbup:

You probably got Dr. Pulley roller weights. Those are the only ones I've heard of that are not round. As for the shifting, I find it odd they would hold the transmission in a lower gear until 25, but it should be normal for them to drop the engine revs at speed.

The only problem I thought of with this would be how to still have the lights work, especially on the back.

That's entirely possible. Maybe I'm mistaken about the lower gearing, but it really sounds like it's revving higher than it used to by 25 for sure.

Do you have a tach or are you going by engine note?

Now that I think about it, I think that is supposed to be one of the benefits of sliders over rollers, in that they won't start shifting until you've gotten going. If you ease off the throttle at 15 mph does the same shifting happen?

As for the better FE, that's natural. Higher vehicle speeds + lower engine speeds + higher engine load = more efficiency.

I can totally see now that it gets those results, it was just unexpected because well, almost nobody around here's gotten this mod and so I didn't really know what it was going to do but I tried anyway. Glad I did! I just also thought it was funny that I've probably been driving way more aggressively too.

The "shifting" will occur slightly earlier if I am not as heavy on the accelerator. Probably 20mph at earliest and 25mph at latest. It seems to have a pretty set shift range "in mind".

There's someone here with a C3 that's modded it way more than I have my own and the results look really positive: Details: Yamaha C3 Scooter - 2007 yamaha C3 Scooter Fuel Economy - EcoModder.com (Check out the fuel logs too). I'm guessing that really really good mileage numbers could be attained if you really made a concerted effort to drive ecomodding style, too.

One thing I've wondered though, that I think would make a huge difference for mileage since I live in a very very hilly area - is there any way to get the equivalent of a neutral gear in my scooter? I know that around 6 or 7mph, when I'm coming to a stop, I can feel something disengage and I actually coast as opposed to having the engine brake, so I know that there's something in there that does it, but I don't really understand the mechanics of it. Being able to coast rather than auto engine brake would make a really big difference I bet.