donny o Posted February 19, 2009 Share Posted February 19, 2009 Replacing piston rings on 1974 DT 125 and all the sets I've found on Ebay are 2 or 3 sizes over. I don't think I need bigger rings--but how do I really know? I have the manual and it explains measuring the cylinder--but I am still confused. I just wonder what's the simplest way to find out what size I do need? And why aren't the standard sets out there? They are all oversized. Thanks Link to comment Share on other sites More sharing options...
Moderator mervin Posted February 19, 2009 Moderator Share Posted February 19, 2009 Donny you need the rings to suit your piston size, your piston will have a number on the crown if that number id .25 .50 .75 or 1.0 then that is the oversize of the piston you may not be able too see the little . very easily these were the yamaha standard oversizes if it is like the RD,s yuo can get pattern pistons in 1.25/1.50.1.75/2.00 as well and the standard pistons came with .96 or .98 stamped on them on RD,s hopefully oldgit who knows far more about DT,s will be along in a minute to help, but larger rings on a standard piston will not work, oversize rings are not a cure for a worn bore Merv Link to comment Share on other sites More sharing options...
01jarno Posted February 19, 2009 Share Posted February 19, 2009 Replacing piston rings on 1974 DT 125 and all the sets I've found on Ebay are 2 or 3 sizes over. I don't think I need bigger rings--but how do I really know? I have the manual and it explains measuring the cylinder--but I am still confused. I just wonder what's the simplest way to find out what size I do need? And why aren't the standard sets out there? They are all oversized. Thanks Hello, I have one boxed DT 125 1st o/s piston,pin,rings and circlips. 1st o/s is 0.25mm As Mervin said, the pistons should be stamped to show the o/s, (if standard size they will have a part number stamed on them instaed) if not then you need an internal micrometer to measure the bore. You also need to evaluate the situation to determine what size you need as the cylinder could be worn or scored. Ideally you need to take this to somebody who knows what they are doing as you cannot explain these things over the internet. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted February 19, 2009 Moderator Share Posted February 19, 2009 best getting a manual as it explains how pistons are oval and wear fore and aft etc. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 19, 2009 Moderator Share Posted February 19, 2009 Cant add much to all the above, you do need to check it doesnt need a rebore before buying new rings, it usually involves inverting the piston in the bore and taking measurements of the gap between piston skirt and bore are you familiar with this donny? as Drewpy says it may be in the workshop manual. Link to comment Share on other sites More sharing options...
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