dtrliam Posted January 7, 2007 Share Posted January 7, 2007 Please help i've recently brought a dt 125, and after having a look over it i decided to have the barrel rebored . after refitting the new piston in the rebored barrel and starting it up. it ran nice on tickover untill abit of throttle was used and then pop. removed the head/barrel and i now have a smashed piston , so purchased a new piston checked the port edges for smoothness replaced everything again started it up. again tickover fine a few revs and then pop . any ideas guys regards liam Link to comment Share on other sites More sharing options...
Moderator YamaHead Posted January 7, 2007 Moderator Share Posted January 7, 2007 What do you mean by "smashed"? Could it be that your Con-Rod is bent?......& did the piston break inside @ the wrist(gudgeon) pin? Or do you have a hole in the top of the piston?....which could mean that you've got a serious air-leak somewhere causing it to run really lean & resulting in the "pop" you spoke of. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted January 7, 2007 Moderator Share Posted January 7, 2007 Please help i've recently brought a dt 125, and after having a look over it i decided to have the barrel rebored . after refitting the new piston in the rebored barrel and starting it up. it ran nice on tickover untill abit of throttle was used and then pop. removed the head/barrel and i now have a smashed piston , so purchased a new piston checked the port edges for smoothness replaced everything again started it up. again tickover fine a few revs and then pop . any ideas guys regards liam I assume that the rings were fitted correctly ie right way round and either side of the locating pegs. Did you have the ports opened? I am thinking the rings expanded into the ports causing the mayhem!! Link to comment Share on other sites More sharing options...
dtrliam Posted January 7, 2007 Author Share Posted January 7, 2007 I assume that the rings were fitted correctly ie right way round and either side of the locating pegs. Did you have the ports opened? I am thinking the rings expanded into the ports causing the mayhem!! yes the rings and pegs located correctly, no the ports have'nt been opened by me perhaps a previous owner/s did ? the piston damage is on the inlet side of the piston in the skirt area and no there is no hole in the top of the piston would a badly ajusted power valve cause a piston to jam ? Link to comment Share on other sites More sharing options...
Recommended Posts