Kymco ZX tips

[lassestyle]

I have a Kymco Super Fever ZX from 2006, and I'm starting to get it really tuned up. As of today, I have a stage6 intake kit, 21mm round slide carb, 70cc kit, Tecnigas bendy exhaust and a performance variator. I also cut off the oil pump throttle line, and I mix my gas and oil about 33:1. What I can tell so far, is that this engine behaves different than other engines. I have tuned other 2 strokes before, but this engine behaves heavier. It's like it's harder to get real performance by just changing a few things here and there.
Is there someone out there that knows of recommended things that I should change out if I want some real power on these ZX, Honda Dio AF28 copy engines? It might be as simple as drilling a bit away in the case, or upgrading an item that is known to perform badly. Please help in any way possible. Cheers!

[aeroxbud]

That is very rich for the premix.
What cylinder, exhaust, and carb do you have? Not all parts are equal. Did you increase the jetting when you installed them?

[lassestyle]

Feb 5, 2024 7:45:46 GMT -5 aeroxbud said:

That is very rich for the premix.
What cylinder, exhaust, and carb do you have? Not all parts are equal. Did you increase the jetting when you installed them?

I have a 70cc kit from a brand called WM Motor, and it is cast iron except the head and piston.

I have a Technicas Next-R exhaust that I've checked for restrictions without any luck. I have yet to check the muffler for restrictions.

I have a Dell'orto 21mm PHBG carburator where I upjetted the main jet from 90 to 99, and downjetted the pilot jet from I think 45 and down to 35/38

I'm running this with a Naraku Racing CDI, Naraku High Tension Ignition Coil, and a NGK BR9HS spark plug.

I had to cut the little nipple off the cable down to the oil pump, so it would allow me to have full throttle in the carburator, and I'm planning to remove the oil pump completely and order an engine plug for a Honda Dio, since it's a copy of a Dio engine. It should be an AF28 model copy.

What premix do you suggest I run? 25:1? I think the oil pump is still working but it's stuck in the standard no throttle position, so it's not pumping much oil.

[aeroxbud]

I've never heard of that cylinder. But if it's a twin ring cast iron it's probably a mild state of tune. The next R is quite a mild exhaust too.
You need to remove that oil pump, or drive. You will never know what amount of oil you are using otherwise. I would certainly not go above 40:1, and all the sports cylinders I have run have been 50:1.
The more oil you use the leaner the engine will run.

[lassestyle]

Feb 6, 2024 15:49:47 GMT -5 aeroxbud said:

I've never heard of that cylinder. But if it's a twin ring cast iron it's probably a mild state of tune. The next R is quite a mild exhaust too.
You need to remove that oil pump, or drive. You will never know what amount of oil you are using otherwise. I would certainly not go above 40:1, and all the sports cylinders I have run have been 50:1.
The more oil you use the leaner the engine will run.

I've been thinking about a 50:1 but I like driving aggressively and I feel like it would need more oil in that situation. Also since it's cast-iron it will need longer time to break it in so I can unleash the full power, but I feel like more oil allows me to go over the top.

Also there aren't really many exhausts for my scooter model. I've heard that people have had great experiences and high speeds with the Tecnigas Next-R exhaust, and I'm guessing any 70cc kit would work since they're all pretty much cast the same. Maybe mine weighs a little bit more and is a little rougher around the edges than a 70cc from a big brand, but it all just comes down to how you treat it, and how well you can squeeze the performance out of it. I'm gonna try taking the kit off at some point soon, and try to dremel out the rough edges and port it a little bit.

[aeroxbud]

As long as your jetting is correct. It shouldn't make much difference. You could always fun it at 40:1 though.
With the cheap cylinder kits it's not just about the casting. Sometimes the port durations are all wrong. Giving very little performance.

[lassestyle]

Feb 7, 2024 15:45:33 GMT -5 aeroxbud said:

As long as your jetting is correct. It shouldn't make much difference. You could always fun it at 40:1 though.
With the cheap cylinder kits it's not just about the casting. Sometimes the port durations are all wrong. Giving very little performance.

Are there tutorials on how to time the ports for best performance?

Also I've been using a jetting technique for a long time where you keep jetting up until you hit the jet where it starts four-stroking, and then using the jet right before it does that, but it's pretty hard to know if you've hit the correct jet on a new cylinder, since you can't really hold the throttle all the way open to check the color on the spark plug. What do you recommend for finding the right jet on a new sports cylinder?

[aeroxbud]

There are quite a few guides online on port timing. We have a data base here. 49ccscoot.proboards.com/thread/176
If you measure yours, it should give you a pretty good idea looking through the link on what level of performance your cylinder is comparable to.

With jetting I always start large, then work down till it runs clean. If you start with something around a 100. It should run terrible.
If it's really bad you don't need to go down each individual jet size. You could miss a few sizes till it gets closer to ideal.
If you start small you will always fun the risk of running lean.

[mopedmofun]

This post shows how much smaller ports are over an elite. Found it pretty interesting. 49ccscoot.proboards.com/thread/21116/comparison-honda-elite-kymco-swapability

I run my zx at 32-1. An old head moped guy told me it’s better. He seemed pretty knowledgeable, so that’s what I do.

My bike goes 40-45 stock.