over heating
any atv without a radiator will get hot as hell if you dont let them cool off every 30 min of riding or so. it also depends on how fast you go becouse thay are air cooled so if you like putting around do it in a higher gear so the engen dosent have to work as hard and get as hot. if you dont let them cool off thay will start sputtering and if you dont stop thay will crack the block or the head from exessive heat. I have to let mine cool off or it will start burning my leg. I own 2 trx250x as well a 87 and a 92. the 92 had a knocking like yours and gave blue smoke out the back soo im going to bore it as well and new pistion rings and ill also check the bearings in the camshaft for ware. I'm glad you figured it out!! this is my second one and I just joind the forums or i would of helped you sooner.
any atv without a radiator will get hot as hell if you dont let them cool off every 30 min of riding or so. it also depends on how fast you go becouse thay are air cooled so if you like putting around do it in a higher gear so the engen dosent have to work as hard and get as hot. if you dont let them cool off thay will start sputtering and if you dont stop thay will crack the block or the head from exessive heat. I have to let mine cool off or it will start burning my leg. I own 2 trx250x as well a 87 and a 92. the 92 had a knocking like yours and gave blue smoke out the back soo im going to bore it as well and new pistion rings and ill also check the bearings in the camshaft for ware. I'm glad you figured it out!! this is my second one and I just joind the forums or i would of helped you sooner.