Originally Posted by Agreen
I've heard terrible things about those CAG engines. I have zero first hand experience with them though, so take it as you will.
Definitely doable. There's a few people who have done it before.
[B]Here is some information I found useful
We have identified four different types of engines used in the Cagllari (Cag) Pocketbike. They are:
1. SY Engine
2. ZH-1 Engine
3. BD Engine
4. 48cc Engine
The SY, ZH-1, and BD engines, are all basically the same, design-wise, but there are little differences between the engines that I will point out (also, remember that the tolerance factors between the engines are so great, that there may be a few SY engines that perform better than ZH-1, BD, etc, and vice versa).
It has been shown, that the ZH-1 has bigger intake ports (look inside the cag's head, and you will see two ports, one on opposited ends of the head) than the SY head. Bigger ports will give you higher RPM numbers, but the low end will be somewhat decreased due to a larger surface area. Remember, bigger isn't always better. There is a sacrafice. With bigger ports, air/fuel velocity will be decreased, but again, since more air/fuel is introduced, you will reach higher RPMs. Again, since the tolrance levels are not that great with these engines, you will find that some SY engiens will perform better overall than the ZH-1 engines. I'm not familiar with the BD engine, to give a thorough review.
The 48cc engine, compared to a ZH-1, has noticeably bigger intake ports, as well as the piston is bigger. This engine is commonly referred to as having the Big Bore kit. This engine, is definitely faster than any of the stock cag engines. The power is greater at all ranges, low, mid, and high. If you're lucky enough to find one of these engines stock on a cag, congratulations. How can you tell or look for one of these engines on a stock cag? You pretty much can't tell the difference, without taking off the head and measuring the bore and stroke. It's a pretty much hit and miss type of deal.
Stock Performance in mph
The following are approximations:
SY, ZH-1 and BD engines - 30 mph (+/-) at 9500-10,000 RPMs
48cc engine - 33 mph (+/-) at 11000 RPMs