midnighttoker Posted January 7, 2004 Report Share Posted January 7, 2004 My shee died on me so i took apart the top end and found out that one of my crankshaft bearings exploded and shot metal in the case. there were also metal chips on the top of the piston and in the exhaust pipes. i was wondering how this is possible because the rings were still on the pistion and i thought stuff from below couldnt go ubove and vise versa. also i dont see any visible damage to the cylinders so do you think i should still have them bored since ive never done it before or just get new pistons? thanks for all your help.... Quote Link to comment Share on other sites More sharing options...
Dextreme Posted January 8, 2004 Report Share Posted January 8, 2004 When a crank goes, metal finds it way into weird places. Before you go to the trouble of replacing your top end, have your cases inspected. If the crank separated (before it blew) and wore into the cases, you will probably need new cases. Quote Link to comment Share on other sites More sharing options...
midnighttoker Posted January 8, 2004 Author Report Share Posted January 8, 2004 it wasnt the crank that broke, thats fine. it was the bearing between the rod and the crank. Quote Link to comment Share on other sites More sharing options...
fixitrod Posted January 9, 2004 Report Share Posted January 9, 2004 Two strokes are different from 4 strokes. I'm chiming in because no shops have and it'll get this moved to the top. If you look how a two stroke works, the fuel mixture comes from the carbs to the intakes.... from the intake to the crank to lube it ... to the transfers and to the top of the piston. When a two stroke blows... it blows. If a crank bearing breaks, it usually take the bore, cylinder and head with it. If a piston skirt goes, it usually take the bore, head, and either takes the crank or gets if full of debris. This is why it its recommended to change your pistons before they make you change them. Check out this link to see the 2 strokes. Here's a pic. Quote Link to comment Share on other sites More sharing options...
shortys racing Posted January 9, 2004 Report Share Posted January 9, 2004 it wasnt the crank that broke, thats fine. it was the bearing between the rod and the crank. actually the charge from the transfer runners blow fuel and air to the top of the piston just before the compression stroke. So when the piston is completely down it is feeding fuel & air and pieces of metal from the bottom end if it's down there. The picture above is a rotax style engine (older snowmobile), that engine is case inducted. Quote Link to comment Share on other sites More sharing options...
jstdrag Posted January 9, 2004 Report Share Posted January 9, 2004 Right on,,, or a old LT250,, lmao Quote Link to comment Share on other sites More sharing options...
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