I'm a mechanic at a motorcycle shop that also does a lot of work on scooters, and we recently had a customer come in with a brand spanking new Kymco Agility 50 who wanted us to make it go faster. This post is about that experience.
We started with a 90cc Hoca kit, a performance camshaft, and a big-valve head, but we retained the stock carb. Performance was lackluster, disappointing at best. The scooter really didn't go much faster. We then played with the rollers, changing the stock rollers for aftermarket 5g sliders, which was also disappointing. We then got the scooter to do 40-43mph using 9g rollers. The owner was happy, but he called us back a week later asking for the "next step." He really wanted to keep up with traffic on roads where the speed limit is 45mph.
We opted to install a stock carb from a GY6 (150cc). When we installed the 90cc kit, we didn't bother looking inside the stock intake manifold. How does that happen? Well we just unbolted it from the head and pushed it out of the way, lol.
When we installed the new carb/manifold/filter, lo and behold we discovered there was a restrictor installed in the stock manifold that measured a whopping 10mm. We figured the scooter would haul the mail with the new GY6 carb/manifold/pod filter, but after installing it and riding the bike we found that it would hit 50mph on flat ground, but it didn't feel right at low speeds. We also found it hit a "wall" at 43mph, so we tried a performance CDI box. It didn't jump off the line like it should, but at high speeds it screamed, and 50mph was easily attainable.
Just because a bike screams at high speeds doesn't mean it's suitable for use by someone who rides daily. Being able to keep up with traffic when a light turns green is more important than the way a bike pulls from 30mph to 50mph. 0-30mph is critical in traffic, soooo.....
We swapped the GY6 carb for the stock carb with the restrictor removed. Top speed didn't change, but the scooter jumped off the line much better. It felt much more like a stock scooter (but quicker...), and we didn't have to give up any top speed. We put a lot of bloody time into this thing, doing our best to make it right. We did the work on our own time, just to figure it out.
We knew the customer wanted more, so we yanked a trick transmission kit (with a whopping 5 miles on it...) off of one of our Honda Ruckus' and installed it on the customer's bike. The bike isn't quite "violent" off the line (it's a scooter!) but the improvement is noticeable. When we called our customer with all the details, he said he definitely wanted us to keep the trans kit and CDI in it and he appreciated our efforts figuring out the carb issues and the fact we were super honest about the big carb.
Thing is... we have a Chinese scooter we did this same 90cc kit with, and it SCREAMED off the line. It pops wheelies. We expected the kit to do the same on the Kymco, and the fact it doesn't is frustrating. If you have any insight, please share. :-P
We made a video of the big-bore kit install, too. I can link to it if you want to see it.
And of course if you have any questions I'd be happy to answer them. :-)
Best,
AR
