How to determine engine cc's with little or no disassembly

[PocketRocket]

If you have an air cooled pocket bike, you might want to read on...

Not all air cooled pocket bike engines are created equal. Did you know that air cooled pocket bikes are advertised and sold as 40cc, 47cc and 49cc. Then there are "big bore" 50cc mod kits that can boost your bike's performance even further. The simple truth is there are only two sizes of engines that come from China. 40cc & 49cc. There is no such thing as a 47cc pocket bike engine. A 49cc bike will be noticably faster than a 40cc bike. To further complicate matters, some retailers sell 40cc bikes with so-called "big bore" kits that are actually 49cc heads. So really it's just a 49cc bike. There are some legitimate performance upgrade parts available which can increase performance of both 40cc and 49cc engines. These include high compression heads and actual mod kits to increase the engine size beyond 50cc.

So how can you tell what you have? The only sure way is to take the engine apart and measure the displacement. If that isn't possible for you, there are a couple of easy things you can do to check the engine size.

1. Take the head off the crankcase. With calipers or a metal scale, measure the bore. If the inside diameter of the cylinder is ~40mm then the engine is likely a 40cc displacement. If the inside diameter of the cylinder is ~44mm then it's a 49cc engine.

2. Still not comfortable with taking parts off your engine? Then here's another way. Look at the cooling fins on the cylinder. The bottom four fins on a 40cc engine are connected all the way around the cylinder. The bottom four fins on a 49cc engine are not connected all the way around.

Remember: The only sure way to tell is to measure the bore and stroke.

[ibrcn]

James,

Any chance you can share that little fuel ratio program or have a way we can use it here?
Keep the info coming, water cooled too. I'll be paying attention...

Cheers

[PocketRocket]

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