piston sizes

[benckie]

if you have brought a second hand motor and not sure of the engine size, or brought a head kit and not sure of the engine size, this is a guide.

32mm poistons are 23cc with a 28mm crank

34mm pistons are 26cc with a 28mm crank

35mm pistons can be 27cc with a 28mm crank or 29cc with a 30mm crank

36mm pistons can be 28.5cc with a 28mm crank or 30.5cc with a 30mm

cy motors with have markings on them to let you know, but zen do not.

for example

a cy motor with 32-28 means 23cc with a 28mm crank

a cy motor with 35-28 means a 27cc with a 28mm crank

a cy motor with 35-30mm means 29cc with a 30mm crank

 

[46u]

23 is actually a 22.5cc
26 is actually a 25.4cc
27 is actually a 26.9cc
Yes they round up to the next highest full CC.

 

[benckie]

a 28.5 is actualy a 28.5cc

a 29cc is actualy a 28.9

a 31cc is actualy a 30.3cc and but is called a 30.5cc

people say a 30mm crank adds 2 cc but actualy it adds 1.8cc

people say a 29mm crank adds 1cc but its more like 0.9cc

there are other combinations also

+1mm or +2mm

23.3cc or 24.2cc

26.3cc or 27.2cc

27.8cc or 28.7cc

29.4cc or 30.3cc





ive just gone from what the engines are sold as meaning zenoah call the 25.4cc a 26cc, cy call there 25.4cc a 26cc.

every one knows they are over estermated, it much easyer to say 23cc and it souns better then 22.4cc, real car makers, motor bike makers have been over estermating cc and engone size for years, it easyer to say and sounds better.

guys say ive got a 1100 cc motor bike, but its actualy 1048cc or peolpe say ive got a 5 ltr gm in my car but is normaly closer to a 4,9 ltr or you buy a 2ltr sports car 2ltr basicly means 2000cc but you will find its more like a 1900cc car, you can not actualy make a engine thats spot on even cc numbers its pritty much mathmaticaly imposible its just the way things are.

and for new guys to the hobby its just easyer to say 26cc as thats what they see on the side of there motor, and ive had arguements about this with people who don't have a clue, so i say 26cc where any one who has half a clue will know the motor is actualy slightly smaller.

the measurements ive give on the piston sizes are spot on, but the cc is over estermated from 0.1 to 0.6cc going by what cy and zen call there motor to keep things simple.

you can over think things or over explain things i tryed to keep this post simple, and give people a refrence if they have brought a used or secondhand motors and they where not sure, as i get asked this alot.

there is a saying i like k,i,s,s = keep it simple stupid, it makes life simple and its normaly easyer for people to understand.

 

[benckie]

well that was fun

 

[46u]

Thanks yes it is fun.

 

[voo2doo]

Jeeze lads these engines are cut rough,whats the difference in a few thou of an inch!
J.

 

[benckie]

Jeeze lads these engines are cut rough,whats the difference in a few thou of an inch!
J.

with a engine lots

just explaining why i used 23,26,27,29cc the same as cy and zenoah use

well im off to the shed to play with my g260pum sorry g25.4pum