malvaro Posted September 1, 2009 Report Share Posted September 1, 2009 Hi guys: do you know? whats the clearence between the pisto .50 and the cilinder? please help me. Quote Link to comment Share on other sites More sharing options...
sheefreak Posted September 1, 2009 Report Share Posted September 1, 2009 Hi guys: do you know? whats the clearence between the pisto .50 and the cilinder? please help me. That is way too big of a number. .50 is a half inch. You need to be in .003 to .005 or sixish. Quote Link to comment Share on other sites More sharing options...
malvaro Posted September 1, 2009 Author Report Share Posted September 1, 2009 Hi: thanks for your help, the new piston's iam gonna put are 64.50mm, i just need to know between 64.50mm and the cilinder the measure. thanks. Quote Link to comment Share on other sites More sharing options...
spurdy Posted September 1, 2009 Report Share Posted September 1, 2009 Hi: thanks for your help, the new piston's iam gonna put are 64.50mm, i just need to know between 64.50mm and the cilinder the measure. thanks. 0.003" - 0.005" or 0.0762mm - 0.127mm SP Quote Link to comment Share on other sites More sharing options...
blowit Posted September 1, 2009 Report Share Posted September 1, 2009 0.003" - 0.005" or 0.0762mm - 0.127mm SP Those numbers are precisely how cast pistons get a bad name. Forged pistons will require .003" but cast pistons will require only .002-.0028" clearance. If you setup cast pistons at .005", they may fail quickly. Brandon Quote Link to comment Share on other sites More sharing options...
spurdy Posted September 1, 2009 Report Share Posted September 1, 2009 Those numbers are precisely how cast pistons get a bad name. Forged pistons will require .003" but cast pistons will require only .002-.0028" clearance. If you setup cast pistons at .005", they may fail quickly. Brandon Sorry man, didn't even consider someone running cast pistons. I've always used Wiseco forged pistons and thought most people did as well. Cast pistons don't require as much of a gap due to the process of manufacturing them. Since they are molten and poured into a mold the grains of the metal are allowed to equally settle where as a forged piston is pressed into shape and the grains of the metal are very irregular and produces a lot of internal stress in the metal. A forged piston will swell more when it is heated then a cast piston will. I should have asked which pistons he was using before I gave the tolerances from wiseco. My bad. Shannon Quote Link to comment Share on other sites More sharing options...
malvaro Posted September 3, 2009 Author Report Share Posted September 3, 2009 Hi guys, iam gonna use oem Pistons are those are cast or forget? please help. Sorry man, didn't even consider someone running cast pistons. I've always used Wiseco forged pistons and thought most people did as well. Cast pistons don't require as much of a gap due to the process of manufacturing them. Since they are molten and poured into a mold the grains of the metal are allowed to equally settle where as a forged piston is pressed into shape and the grains of the metal are very irregular and produces a lot of internal stress in the metal. A forged piston will swell more when it is heated then a cast piston will. I should have asked which pistons he was using before I gave the tolerances from wiseco. My bad. Shannon Quote Link to comment Share on other sites More sharing options...
hercalmighty Posted September 3, 2009 Report Share Posted September 3, 2009 Hi guys, iam gonna use oem Pistons are those are cast or forget? please help. OEM is cast. What size are you looking at? .50mm or 0.050" over stock? Quote Link to comment Share on other sites More sharing options...
malvaro Posted September 3, 2009 Author Report Share Posted September 3, 2009 64.50mm 0.50mm yamaha oem thanks for your help. OEM is cast. What size are you looking at? .50mm or 0.050" over stock? Quote Link to comment Share on other sites More sharing options...
spurdy Posted September 3, 2009 Report Share Posted September 3, 2009 64.50mm 0.50mm yamaha oem thanks for your help. I was going through the assembly of a top end for a buddy last night and noticed the clymer service limit on oem pistons is 0.002" - 0.006". So it seems that the clearance for the cast piston has a lower minimum being at 0.002" and a maximum of 0.006" before needing rebuilt without failure. SP Quote Link to comment Share on other sites More sharing options...
malvaro Posted September 16, 2009 Author Report Share Posted September 16, 2009 ok guys, finally I bought wiseco M series Piston kit so, piston to cilider clearance its 0.003" any suggestion with the rings? and the holes i need to make to lubricate the pistons? thanks Mariano Alvaro I was going through the assembly of a top end for a buddy last night and noticed the clymer service limit on oem pistons is 0.002" - 0.006". So it seems that the clearance for the cast piston has a lower minimum being at 0.002" and a maximum of 0.006" before needing rebuilt without failure. SP Quote Link to comment Share on other sites More sharing options...
hercalmighty Posted September 16, 2009 Report Share Posted September 16, 2009 The rings should be about 0.010-0.012 ring gap. If you have stock cylinders you dont need the oiling holes. You only need those if you have an exhaust bridge. Quote Link to comment Share on other sites More sharing options...
malvaro Posted September 16, 2009 Author Report Share Posted September 16, 2009 yes iam with that stock cilinder, thanks for your help. what exactly exhaust bridge? The rings should be about 0.010-0.012 ring gap. If you have stock cylinders you dont need the oiling holes. You only need those if you have an exhaust bridge. Quote Link to comment Share on other sites More sharing options...
hercalmighty Posted September 16, 2009 Report Share Posted September 16, 2009 Most dirtbikes have a dual exhaust port. So there is a little piece of metal that separates the two ports. That little bridge heats up alot faster then everything else so it will expand faster. So to help with that you put a couple holes in the piston for oiling. Quote Link to comment Share on other sites More sharing options...
malvaro Posted September 16, 2009 Author Report Share Posted September 16, 2009 thanks I got it!! Most dirtbikes have a dual exhaust port. So there is a little piece of metal that separates the two ports. That little bridge heats up alot faster then everything else so it will expand faster. So to help with that you put a couple holes in the piston for oiling. Quote Link to comment Share on other sites More sharing options...
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