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what causes thrown rod?

This is a discussion on what causes thrown rod? within the Yamaha YFM660R Raptor (2001-2005) forums, part of the Performance /Technical category; i reacentley got another 03 raptor 660 and it had threw a rod through the cases i have replaced it but im wondering what caused ...


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Old 02-10-2010, 11:59 PM   #1
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i reacentley got another 03 raptor 660 and it had threw a rod through the cases i have replaced it but im wondering what caused this ? the oil pump works . i noticed a dent in the radiator but no leeks would that caus it to over heat and throw a rod ? the one way is great the clutch plate on the back was shattered . the piston and jug were stock and are again stock with high com piston 11.1-1 i dont want to start it and have it fall apart is there anything i should cheak first ?
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Old 02-11-2010, 07:26 AM   #2
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Did this engine have the hotrods crankshaft like explained in your other posts? Also was it an oem replacement or stroker crank? Fill us all in with as much info as possible.
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Old 02-11-2010, 08:05 AM   #3
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Usually over-revving. Big cams let the engine spin faster and high compression puts more stress on things.
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Old 02-11-2010, 01:09 PM   #4
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simple things like never changing the oil, never cleaning the air filter and stuff can easily blow an engine up, runnign with no oil, or no water, or even sometimes, it just happens, machines and going to fail, and sometimes they fail catastrophically... which is the perfect definition of a thrown rod. something broke, and a chain reaction leads to all hell breaking loose.
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Old 02-11-2010, 01:14 PM   #5
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the motor was blown when i got it and it was a stock crank oem.
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Old 02-12-2010, 03:25 AM   #6
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I would say over reving is the biggest problem.
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Old 02-12-2010, 07:34 PM   #7
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Quote: Originally Posted by leveldrummer View Post
simple things like never changing the oil, never cleaning the air filter and stuff can easily blow an engine up, runnign with no oil, or no water, or even sometimes, it just happens, machines and going to fail, and sometimes they fail catastrophically... which is the perfect definition of a thrown rod. something broke, and a chain reaction leads to all hell breaking loose.
please explain how a dirty air filter can cause a rod to snap? i have heard it all now....over reving the motor causes rods to snap end of story
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Old 02-13-2010, 10:39 PM   #8
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Quote: Originally Posted by heater View Post

please explain how a dirty air filter can cause a rod to snap? i have heard it all now....over reving the motor causes rods to snap end of story
The dirt builds up on the bottom of the cylinder. Pretty soon the bottom of the cylinder is necked clear down. Then as the conectiong rod is rotating, the conecting rod hits the hard dirt ring.
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Old 02-13-2010, 11:08 PM   #9
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Quote: Originally Posted by heater View Post
Quote: Originally Posted by leveldrummer View Post
simple things like never changing the oil, never cleaning the air filter and stuff can easily blow an engine up, runnign with no oil, or no water, or even sometimes, it just happens, machines and going to fail, and sometimes they fail catastrophically... which is the perfect definition of a thrown rod. something broke, and a chain reaction leads to all hell breaking loose.
please explain how a dirty air filter can cause a rod to snap? i have heard it all now....over reving the motor causes rods to snap end of story
when all the sticky oil has dirt packed into it, then dust gets through, into the cylinder, scratches it up, causes lock up, and catastrophic engine failure, sure it wont just cause the crank to snap, but it can sure ruin an engine, and cause failure, which will lead to a crank breaking etc...

point is, lots of things cause engines to blow,
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Old 02-14-2010, 02:18 PM   #10
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the silinder and piston were dameged. but i was just wondering i realy dont want that to happen to me . i took it out the other day it did realy well till i tried to climb a 9' hill it started to slow down so i hit the throttle and almost fliped it . i got it down and when it died i restarted it and it ran good but i knew something was wrong cheaked the timeing and my woodruf key was sheered the flywheel was spining every once and a while it would catch . i built the bottom end and put the flywheel on but dident torque it up becaus the top end wasent on and its easier to get it torqued up as a compleat motor for me anyways . but i got a key today and its back up and running .
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