sezian Posted March 13, 2009 Share Posted March 13, 2009 After having removed the head, barrel and piston for a good de-coke I find a very thin spacer / oil control ring sitting under / behind the second piston ring. Looking in all the manuals and on the web there doesn’t appear to be any reference to this ring ??? I believe it to be an oil control ring ? but not totally sure why it’s fitted, I must admit it was a bit of a shock to find it hiding away in the piston groove. I don’t recall coming across a ring like this when rebuilding a 2 stroke previously. Anyway I believe it should be replaced on reassembly which is fine as I know where it came from however the 2 piston rings seem slightly different and I’m not sure which ring came out of which groove ? Does this matter ? The only difference with the rings appears to be one has a slightly bigger gap giving it slightly more spring when fitted ( trust this makes sense ), this I presume will give slightly more friction when the barrel is fitted. I have measured the rings in the bore and they are well inside tolerance the bigger gap I refer to is only when lose not when compressed. Any advice or info on this ??? Please help before I rebuild the engine. Link to comment Share on other sites More sharing options...
shed hermit Posted March 13, 2009 Share Posted March 13, 2009 i think it is an oil ring, i have the same ring is on the rd. the piston rings are a slightly different thickness, the best way to find whether they are top or bottom is to slip it into the groove i.e. piston on one hand and ring in the other and not by slipping them on,(in case they break) you should have a small bit of play on both rings doing it this way. i think the oil? ring comes with the new set of rings anyway, Link to comment Share on other sites More sharing options...
Moderator mervin Posted March 13, 2009 Moderator Share Posted March 13, 2009 Ok your thin ring. oil control on a 2 stroke i dont think so. it is called an expander ring behind thickest ring in bottom groove, thinnest ring goes in the top groove, if your thick ring will go in the top groove then i would replace the piston and ring, as the ring grooves are worn in the piston and the ring will move up and down as the engine is running waering away even faster eventually slipping out breaking and ruining your bore, Merv Link to comment Share on other sites More sharing options...
sezian Posted March 14, 2009 Author Share Posted March 14, 2009 I've measured each ring with a micrometer and they are both identicle thicknes, they both go in either top or bottom groove and would apear to be interchangeable ??? I was unaware that each ring is made as a different thicknes ??? This seems strange as there would be extra manufacturing costs, what should the difference be in thicknes ??? If anyone has anymoe info on this please post. Thanks. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 15, 2009 Moderator Share Posted March 15, 2009 They are bothe the same on the 175MX, place the thin spreader ring under ring 2 Link to comment Share on other sites More sharing options...
sezian Posted March 16, 2009 Author Share Posted March 16, 2009 Any reason why one ring should have slightly more spring than the other ? Does it matter where this ring goes ? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 16, 2009 Moderator Share Posted March 16, 2009 Any reason why one ring should have slightly more spring than the other ? Does it matter where this ring goes ? No I dont think this difference is intentional, doesnt matter which groove you put them in. Cant you see any marks on the inside of the rings caused by this spacer ring (bright spots) that may give a clue as to which ring came from which groove, have a look with a magnifying glass. Link to comment Share on other sites More sharing options...
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