How to identify your engine size

Hi,
There are two types of engines fitted to Chinese mini's and midi's. Both types of engine come in two sizes depending on the cylinder fitted in the factory.

The first type claim to be 47cc and are fitted MK1's MK2's (also know as Cagllari's and many other names).
Some are actually 47cc cylinders but most are 39cc. both have the same crankcase, crank and Carb. The way to tell which cylinder you have is to look at the cooling fins on your cylinder, in particular to the bottom four cooling fins closest to the crank case. On 39cc cylinders these fins go all the way round the cylinder unbroken, from one side of the exhaust port all the way round the cylinder to the other side of the exhaust port without breaking. On a 47cc head the bottom four cooling fins stop at the corner of the cylinder (above the bolt holes) and then start again after the corner.

Here is a picture of both cylinders

http://img6.exs.cx/img6/7441/BigBore.jpg

The one on the right is a 39cc:mad: head. Look at the bottom four cooling fins, they go all the way round without breaking.
The cylinder on the left is a 47c:thumbsup: . Ignore the head, the cylinder has been cut to fit the head off a Honda engine. Look at the bottom four cooling fins. They don't go all the way round, they stop at the corners or the cylinder and the bore sticks through. The bore is bigger so if the fins went all the way round the cylinder there would be no way to get an Allen key to the bolt and nowhere for the bolt to go when you unscrew it (if you could). Can you see what I mean?
To make thing more interesting there are at least four types of 39cc cylinders fitted to these engines.

SY cylinder
ZH-1 cylinder
BD cylinder
and unmarked 39cc cylinders (there could be any number of different unmarked cylinder types)

They all perform roughly the same except for minor difference's I.E. the ZH-1 has slightly bigger transfer ports than the SY so it will rev a little bit higher but will have less bottom end.
The marking is on the side of the base of the cylinder (behind the top engine mount). remember it may not be marked.
47cc cylinders are not marked.

The other Type of engine is the claimed 49cc engine.
These are either cloned Mitsubishi engines and are 49cc or 43cc. They are fitted to Chinese Midi bikes (Cateye's, Daytona's, MK3's and many other names) and many other scooters. They are both less powerful than the 47cc type motors. This is because the 47cc type engines are reed inducted (have reed valves) and the Mitsubishi clones aren't.
The only way to tell which cylinder you have on your Mitsubishi clone engine is to remove the cylinder.

http://img6.exs.cx/img6/4221/image146.jpg


Here is a picture. Look at the skirt of the cylinder.
You are looking for the groove on the side of the cylinder skirt pointed to by the arrow. If you have the groove then it is a 43cc:( , if you don't you have a 49cc cylinder:p .

Good luck
Richard Lea

If you have the engine apart, you can measure it.
Radie<--dont know if it's the right word but it's half the cylinders diameter.

Radie x radie x 3,14 x stroke 33mm?

22 x 22=484 x 3,14=1519,76 x 33 = (50,152,08cc's)

20 x 20=400 x 3,14=1256 x 33= (41,448cc's)

Cheers!

I Am Seriously Lost We Are Starting A Pocket Race Team To Compete In Events And Work O Them As An Alternative To Theangs For The Kids,i Came Across A Yellow Mini Wth Suzuki Stickers And A Blue One With A Cvt Going To The Rear I Need Help Please Reply

The images are broken

someone please fix....

Really appreciate the info! I have a working background (High School) on small engine repair and we went to PSU back in the day for small engine repair competition. On a side note, upon arrival, small engines weren't on our mind...so you can imagine where we placed! Now, seems like a century later (haha), I took on a project trying to get a friends "sitting" pocket bike running and had no info available from him on the bike at all. No spark, so I t-shot it down to the ignition coil, but to repair it ya have to know what your working with! Your post has definitely put me on the right track and I again can't stress how much I really appreciate your info! Took me less than a minute match our notes to properly ID the correct "cc ID". Now I can move forward, and I'm certainly keeping a log as I go, for future repairs. Next I will see if I can t-shoot the ignition unit itself.