Normaly the only damage is caused by misadjusted RC valves. When the valve is at the closed postion the valve rests on the port wall and can sometimes wear two small holes (one on each side).

If this is the sort of damage that has been caused then normaly alittle work with some fine paper in the port can remove the sharp edges where the valve has worn the port and it will be good to go again.

Make sure when you rebuild the cylinder that with the servo in the low postion the valves are just clear of touching the port wall.
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If I have to take the carbs off once more...