What size is this piston?

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
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up north now
Measure it across the widest point. It could be from an engine anywhere from 45cc to maybe 49cc.
I've built kits in the range from 45 to 68cc's.
 

bioboi

New Member
Apr 30, 2020
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Please help!! I know the differences between model a and b it is a type a but this piston is all around smaller
width is 25mm length is 30mm it has a rounded top
 

Larry Trotter

Active Member
Nov 26, 2017
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I don’t think it’s 25mm. 25mm is about an inch and yours looks like about an inch and a half.
 

bioboi

New Member
Apr 30, 2020
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I don’t think it’s 25mm. 25mm is about an inch and yours looks like about an inch and a half.
I went out bought a ruler it says 38mm it this correct? just got my stimulus money yesterday and bought an engine but i still want to fix this one for backup!
 

Larry Trotter

Active Member
Nov 26, 2017
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It may be easier to replace both cylinder and piston if this set fits. There are many of these on eBay so look at a few.