What would have caused this scarring on the cylinder wall?

R

Rexx Shyt

Member
Like I said in my previous post a neighbor gave me motorized bike and when I took it apart this is what I found and I can't for the life of me figure out what could have done this... so any input would be appreciated. Take a look at the pics.
 

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Rexx Shyt said:
Like I said in my previous post a neighbor gave me motorized bike and when I took it apart this is what I found and I can't for the life of me figure out what could have done this... so any input would be appreciated. Take a look at the pics.
Click to expand...
This is a chrome plated cylinder. Very thin. It was manufactured improperly. Most of them are. What you have right there is a cylinder worn out. When the chrome plating flakes off the aluminum bore your pictures show the result. Over time this will result in power loss and a no start condition. Eventually you got 0 compression.
Greg makes an excellent point. when you get a new engine / or kit you must inspect the cylinder walls for debris and spalling. I have received brand new cylinders with the chrome plating flaked off right out of the box. Right now you need a new Cylinder and Rings.
 
I have a couple of rotary tools but find the cheapest one from harbor freight to be the easiest to use on ports, its not that powerful so I have to go slow, that prevents mistakes. I ordered long shank carbide rasps from Amazon, I taper the ports to prevent rings from snagging the ports.
 
Greg,
Are you using / buying iron sleeved cylinders exclusively? Are they readily avail? Can you post a link for the O.P. and the rest of us as to consider an alternative to the plated cylinders?
 
I’ve bought a couple of 49mm bore piston and cylinder sets From eBay, they are not plug and play, they have to be port timed and the cylinder needs to be honed for piston clearance. I have seen standard 47mm iron sleeve cylinders listed as well but haven’t used one.
 
I enjoy playing with the larger engines but still find my little 48cc bikes more fun to ride, my latest 48 is the open transfer type like the G4 that has become more popular.
 
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