Caused slight scratches / pitting when porting engine (pics)

dontworryaboutmyusername

dontworryaboutmyusername

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Was porting my 80cc engine to clean up the junk, was using steel file and a dremel. The dremel slide a few times and caused some scratches / slight pits (see pics). Ive been hand polishing the cylinder with 150 and 300 grit sandpaper to smooth it out as much as possible. These defects are tiny but can be felt with finger. Should these be a cause for concern or should the engine still function normally?
 

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DAMIEN1307 said:
because all of these cylinders have a lining that was applied/bonded to the base aluminum and its quite thin, If you remove that lining by sanding it smooth you will have totally ruined the cylinder itself.
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Damn, never realized this. I did hand sand it so it wasn't as abrasive as say a power tool. What material is this lining? What would happen if I reinstall the engine and drive without this lining (if I did infact sand it completely off)? Would you suggest I just buy a new cylinder or do you think this could still be used?

Also, would these small scratches / pits have any impact?
 
dontworryaboutmyusername said:
Damn, never realized this. I did hand sand it so it wasn't as abrasive as say a power tool. What material is this lining? What would happen if I reinstall the engine and drive without this lining (if I did infact sand it completely off)? Would you suggest I just buy a new cylinder or do you think this could still be used?

Also, would these small scratches / pits have any impact?
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Some may differ, but if it were me, I would get a new cylinder rather than risk any other further damage that could result from piston seizing on the bare, softer, aluminum etc.

Most of the regular, run of the mill China Girls come with just a sliver of chromium lining in them...My engines are a little different, My Zeda 80 and My Phantom 85 are both ceramic lined.
 
DAMIEN1307 said:
Some may differ, but if it were me, I would get a new cylinder rather than risk any other further damage that could result from piston seizing on the bare aluminum etc.

Most of the regular, run of the mill China Girls come with just a sliver of chromium lining in them...My engines are a little diferent, My Zeda 80 and My Phantom 85 are both ceramic lined.
Click to expand...

So the risk due to lack of chrome lining is potential piston seizing? What is the chance of that happening and what would the result be? Will my engine explode or just suddenly stop when riding?

Also - any suggestions on a cylinder replacement? It looks like cylinders have now been "upgraded" and have a different design near the bottom (see image). Is this an improvement? My original engine was here (https://www.ebay.com/itm/383920220520) was advertised as 100c but its more like 80cc or 66cc and am not 100% sure if these replacements would fit it.

example "upgraded" replacements:

www.ebay.com

80cc Cylinder jug (47mm) G4 -B gas motor bike engine 2-stroke | eBay

80cc Cylinder G4 UPGRADED 2-stroke engine motorized bike ( no intake) see first picture.
www.ebay.com
www.ebay.com

88cc Upgrade Cylinder (47mm) For 2 Stroke 66CC 80CC Motorized Bicycle Bike | eBay

66cc 80cc 2 Stroke Engine Motorized Bicycle Bike. 1 Cylinder(47mm).
www.ebay.com
www.ebay.com

80cc Motor bike GAS ENGINE wider intake G4A cylinder 30mm high hole piston rings | eBay

2-stroke wider intake (40mm) G4A cylinder with 1 1/16" or 35mm ( high hole) piston and rings for 66cc, 68.5cc, 80cc 2-cycle engine !
www.ebay.com
 

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I've had a few mishaps like this and mine ran ok, the worse that can happen is you have to replace the top end. I keep several ready in case I need them. Spare parts are a must if you want to keep your bike going, I have three so I have a lot of spare parts, I have two back up engines on the shelf.
 
The best tool for porting for me is the cheapest one harbor freight sells, it lacks the power to do damage and make me go slow preventing mistakes. The larger and more powerful tools dig in and jump around.
 
I don't think you'll have a problem with that cylinder. The fastest I've gone so far, 46mph, was done on a cylinder that was heavily scored. It never blew up, I just replaced it because I don't think it was helping the performance. ;)
 
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