twin segments

S

steppenwolf

New member
Location
france
hi there, struggled with a seized (second) segment till i broke it...now question: why this difference in cross section between first and second segment which , at least on my bike, has a kind of "step"? I it possible to use a "first" segment as a replacement? this would greatly help getting going in the job i am at. Thanks in advance
 
I assume you're referring to piston rings.

No, they are not interchangeable. The upper ring is purely a compression ring, usually hard-chrome plated. The lower is a combined compression/oil scraper, it has a very different cross-section and therefore a defined fitting orientation and is usually unplated cast iron.

Using a plain compression ring in place of the scraper can result in increased oil consumption, along with excessive smoking.

piet
 
thanks piet, yes i meant piston rings. Actually i see there are three rings and the bottom is the oil scraper you've mentioned. My question was about the top (first) and the middle (second) ring: they looks the same except for this "notch" in the cross section. Thanks
 
The lowest ring is commonly referred to as th oil control ring. This removes the majority of oil from the cylinder walls on the piston downstroke, the bores at the bottom of its' groove allow oil to escape to the inside of the pistonn. The second ring scrapes off any excess that might be left, therefore the "notch".

piet
 
It's a good idea to check the freeplay between the piston ring and the piston groove per the "Green Book". And also check the end gaps of the rings and make sure the one ring is facing down- again refer to the "Green Book". The open ends of the rings are supposed to be 120 degrees apart, but one mechanic told me that they spin around and change orientation during use- but others may disagree.
 
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