AndyDtr08 Posted May 16, 2009 Share Posted May 16, 2009 Ok so im doing a top end rebuild of a Dt125 1986 lc. The 2 piston rings i have are exactly the same, aside from th fact that one is slightly thicker. like inside the brackets ( O O ) The only markings on them are 150 and R. Neither of the rings are chamfered. The ends between the end gaps are exaclty the same. The piston ring make is Riken. I am at a loss, anyone used these rings before and could shed some light would become my hero Thanks Andy Link to comment Share on other sites More sharing options...
JimR Posted May 16, 2009 Share Posted May 16, 2009 Ok so im doing a top end rebuild of a Dt125 1986 lc. The 2 piston rings i have are exactly the same, aside from th fact that one is slightly thicker. like inside the brackets ( O O ) The only markings on them are 150 and R. Neither of the rings are chamfered. The ends between the end gaps are exaclty the same. The piston ring make is Riken. I am at a loss, anyone used these rings before and could shed some light would become my hero Thanks Andy Hi Andy, after market rings will fit an aftermarket piston & not perhaps a Yamaha one through the reason you point out i.e different dimensions where as Yamaha ones were the same dimensions perhaps you need to get a piston from same factory ! Regards Jim Link to comment Share on other sites More sharing options...
AndyDtr08 Posted May 16, 2009 Author Share Posted May 16, 2009 Hi Andy, after market rings will fit an aftermarket piston & not perhaps a Yamaha one through the reason you point out i.e different dimensions where as Yamaha ones were the same dimensions perhaps you need to get a piston from same factory ! Regards Jim Good thought. Sorry i forgot to mention, the piston is aftermarket too, i had the barrel rebored at an engineering shop and they supplied the entire piston Kit, which is what they re bored the barrel to. The rings will fit no problem, my only issue is i cant work out which order the rings go, it would be ok if one wasnt slightly thicker than the other. My only thought is that the thicker one would go at the top to create a better compression with the thinner one acting as a backup to catch anything else. "Scooby Doo is less confused than me"! Link to comment Share on other sites More sharing options...
JimR Posted May 16, 2009 Share Posted May 16, 2009 Good thought. Sorry i forgot to mention, the piston is aftermarket too, i had the barrel rebored at an engineering shop and they supplied the entire piston Kit, which is what they re bored the barrel to. The rings will fit no problem, my only issue is i cant work out which order the rings go, it would be ok if one wasnt slightly thicker than the other. My only thought is that the thicker one would go at the top to create a better compression with the thinner one acting as a backup to catch anything else. "Scooby Doo is less confused than me"! Hi Andy/Scooby ? if you have rings of different thickness the grooves in the correct piston would dictate on the correct order. Imust say tho back in the 70's/80's the thiner ring was fitted to the top of the piston Regards Jim Link to comment Share on other sites More sharing options...
Moderator Cynic Posted May 16, 2009 Moderator Share Posted May 16, 2009 Back when i were a t'lad i had a dt50m and i fitted one of the better quality big bores and that had a stepped top ring that made it considerably wider than the one below it, the piston was machined to take it as at extended up the side of the piston by about 2-2.5 mm. Supposedly gave much better compression. Dunno bout that but i dont remember anybody else getting 70mph from 60cc (in perfect conditions)so i can't have been all bad. For my money if one of the rings is visibly thicker then there should be a corresponding difference in the groves. Link to comment Share on other sites More sharing options...
YPVS TONE Posted May 16, 2009 Share Posted May 16, 2009 On my 350 powervalve i have some TKR pistons and the thin ring goes in the top groove .Have you tried fitting the thicker ring in the top groove you will probably find it won't fit. Tony. Link to comment Share on other sites More sharing options...
AndyDtr08 Posted May 16, 2009 Author Share Posted May 16, 2009 On my 350 powervalve i have some TKR pistons and the thin ring goes in the top groove .Have you tried fitting the thicker ring in the top groove you will probably find it won't fit. Tony. Cheers for the replies. As i tried to show in my feeble attempt at a diagram ( O O ) its the thickness like that, not the thickness like this ( - -). The grooves are exactly the same size, i thought of that straight away. Apologies for the Football factory quote, but i really am stuck lol, it doesnt make sense to me unless someones had the piston ring box open and switched them round for a laugh. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted May 16, 2009 Moderator Share Posted May 16, 2009 Cheers for the replies. As i tried to show in my feeble attempt at a diagram ( O O ) its the thickness like that, not the thickness like this ( - -). The grooves are exactly the same size, i thought of that straight away. Apologies for the Football factory quote, but i really am stuck lol, it doesnt make sense to me unless someones had the piston ring box open and switched them round for a laugh. Its probably called radial thickness in proper speak but i know what you mean. The different thicknesses may still be deliberate. Check the depth of the grooves in the piston. The thicker ring will be stronger and at least in theory give a better seal on the bore. The thing is in engineering at least if the mark 1 eyeball can see it its quite a diference. Link to comment Share on other sites More sharing options...
AndyDtr08 Posted May 17, 2009 Author Share Posted May 17, 2009 Its probably called radial thickness in proper speak but i know what you mean. The different thicknesses may still be deliberate. Check the depth of the grooves in the piston. The thicker ring will be stronger and at least in theory give a better seal on the bore. The thing is in engineering at least if the mark 1 eyeball can see it its quite a diference. Ye radial thickness sounds a bit more technical than "like this with 2 O's" ! I genuinly dont think there is any difference in sizes between the grooves though, at 1st i did, but that was because i had the expander ring already in and like those optical illusions, different shades of colour can connote larger sizes. I did briefly measure the gaps, with the end of a screwdriver to.................. .....................upon re read of your post i have decided that i am a wally! I will check the "depth" of the gaps haha! That'll teach me for being stubborn! Right ill go have a look and report my findings Cheers. Hopefully it will be a "fresh pair of eyes" case! Link to comment Share on other sites More sharing options...
AndyDtr08 Posted May 17, 2009 Author Share Posted May 17, 2009 Ive been beaten to it, my dad told me he was looking at it whilst i was at work last night. The depths of the grooves are also identical. Hes stumped as well. Unless anyone else has any other suggestions i reckon ill just put the thicker ring on top, as cynic says with his bore kit. Whats the worst that can happen i mean its not like its a delicate, easily damagable surface anywhere near it =/!!! Link to comment Share on other sites More sharing options...
Moderator Cynic Posted May 17, 2009 Moderator Share Posted May 17, 2009 Ive been beaten to it, my dad told me he was looking at it whilst i was at work last night. The depths of the grooves are also identical. Hes stumped as well. Unless anyone else has any other suggestions i reckon ill just put the thicker ring on top, as cynic says with his bore kit. Whats the worst that can happen i mean its not like its a delicate, easily damagable surface anywhere near it =/!!! I suppose logic say's the higher ring will have to cope with higher stresses being closer to the detonation so that would be where i would put it. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted May 17, 2009 Moderator Share Posted May 17, 2009 I suppose logic say's the higher ring will have to cope with higher stresses being closer to the detonation so that would be where i would put it. I may have missed something here but didnt the original OEM set have an expander ring in the bottom groove? Why not re-use it under the thinner ring? or if you havnt got it put the thinner ring in the bottom groove anyhow. Link to comment Share on other sites More sharing options...
JimR Posted May 17, 2009 Share Posted May 17, 2009 Back when i were a t'lad i had a dt50m and i fitted one of the better quality big bores and that had a stepped top ring that made it considerably wider than the one below it, the piston was machined to take it as at extended up the side of the piston by about 2-2.5 mm. Supposedly gave much better compression. Dunno bout that but i dont remember anybody else getting 70mph from 60cc (in perfect conditions)so i can't have been all bad. For my money if one of the rings is visibly thicker then there should be a corresponding difference in the groves. Hi Cynic, My FS1 indicates 62~65 mph in perfect conditions with a 70cc big bore on and the piston does have keystone rings but I guess this type of ring would increase compression, as the compression would be obtained from other factors, but it would maintain the compression better than std type rings Regards Jim Link to comment Share on other sites More sharing options...
AndyDtr08 Posted May 17, 2009 Author Share Posted May 17, 2009 I may have missed something here but didnt the original OEM set have an expander ring in the bottom groove? Why not re-use it under the thinner ring? or if you havnt got it put the thinner ring in the bottom groove anyhow. Im sure i replied to this once, might have been same time my net went down but anyway... Ive got the expander ring in the bottom groove, the new set came with one, but even so ive never come across a set of rings that are the same, or even without the top ring being chamfered to press out during the explosion. I might add the rings are teflon (sp) coated so i dont know if this makes a difference. The Riken wesite doesnt help as it just babbles on about 4 strokes! I think after spending 100 quid of my student loan on the rebore and piston set im gonna wait til 2moro and ring the engineering shop, get their advice, so if it does go wrong i can atleast take it back to them and say, this is what you told me to do. @Old git, im not worried that the bottom ring isnt going to seal properly as it fits the bore nicely, the end gaps is exactly the same on both rings so they are for that bore, im just concerned that im gonna end up scoring the new bore, or doing somthing odd. Its my 1st complete rebuild of any bike, my 02 offroad DT i had the engine out and rebored, but this one is my baby so i want everything to be perfect My friend who i went halves on for the project has pulled out, so alot of money i cant afford is going into her, so dont wanna leave anything to chance. Thanks for all the help guys ill let you know what the shop says! Link to comment Share on other sites More sharing options...
JimR Posted May 17, 2009 Share Posted May 17, 2009 Im sure i replied to this once, might have been same time my net went down but anyway... Ive got the expander ring in the bottom groove, the new set came with one, but even so ive never come across a set of rings that are the same, or even without the top ring being chamfered to press out during the explosion. I might add the rings are teflon (sp) coated so i dont know if this makes a difference. The Riken wesite doesnt help as it just babbles on about 4 strokes! I think after spending 100 quid of my student loan on the rebore and piston set im gonna wait til 2moro and ring the engineering shop, get their advice, so if it does go wrong i can atleast take it back to them and say, this is what you told me to do. @Old git, im not worried that the bottom ring isnt going to seal properly as it fits the bore nicely, the end gaps is exactly the same on both rings so they are for that bore, im just concerned that im gonna end up scoring the new bore, or doing somthing odd. Its my 1st complete rebuild of any bike, my 02 offroad DT i had the engine out and rebored, but this one is my baby so i want everything to be perfect My friend who i went halves on for the project has pulled out, so alot of money i cant afford is going into her, so dont wanna leave anything to chance. Thanks for all the help guys ill let you know what the shop says! oh OK regards Jim Link to comment Share on other sites More sharing options...
AndyDtr08 Posted May 18, 2009 Author Share Posted May 18, 2009 Ok so im doing a top end rebuild of a Dt125 1986 lc. The 2 piston rings i have are exactly the same, aside from th fact that one is slightly thicker. like inside the brackets ( O O ) The only markings on them are 150 and R. Neither of the rings are chamfered. The ends between the end gaps are exaclty the same. The piston ring make is Riken. I am at a loss, anyone used these rings before and could shed some light would become my hero Thanks Andy For anyone who was interested, the guys at boretech confirmed that the thinner BOTTOM ring goes over the expander ring, so the thicker ring goes at the top. Once they said this it dawned on me that i could just find the old piston and rings id removed and see if one was thicker/thinner. They were! A lot of fuss for nothing haha! Atleast i know now and wont do it again Thanks for all the advice guys Link to comment Share on other sites More sharing options...
Moderator Cynic Posted May 18, 2009 Moderator Share Posted May 18, 2009 For anyone who was interested, the guys at boretech confirmed that the thinner BOTTOM ring goes over the expander ring, so the thicker ring goes at the top. Once they said this it dawned on me that i could just find the old piston and rings id removed and see if one was thicker/thinner. They were! A lot of fuss for nothing haha! Atleast i know now and wont do it again Thanks for all the advice guys No worries nice to know it turned out ok. Link to comment Share on other sites More sharing options...
AndyDtr08 Posted May 19, 2009 Author Share Posted May 19, 2009 No worries nice to know it turned out ok. Ill agree with that I put the engine back in the frame earlier, im sure you'll understand the elation when i got the mounting bolts in and stood back with my cup of tea in hand and smug look on the face! I appear to be missing the airbox tho roflcopter! Link to comment Share on other sites More sharing options...
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