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post #1 of 18 (permalink) Old 02-24-2010, 08:20 PM Thread Starter
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Question 300ex motor trouble

ok so when i got it it had had the puston hit the valves i got anouther head with it guy said it was botton end and he gave me anouther so i fix it piston rings and lots of time it was running about a month later i was riding in creak when i got it home it kept cutting out i thought it might have been somthing wet so i kept running it went dead took valve cover off to notice the timing strocket bent and chain off witch allso broke ears off cam replaced cam and sprocket rode it about 3 hours and went dead again took valve cover off and the timing marks were off by 2 or 3 teeth 1 exsaust valve hit the piston hot only 1 valve hit i dont know i dont know iv valve stuck or what but not i got lots of money to spend on it again any ideas why i think it jumped time but botton and top timing sprockets are fine
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post #2 of 18 (permalink) Old 02-24-2010, 08:22 PM
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did you replace timming chain ?..sounds like your timming chain is streched too far..which caused it to jump time
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post #3 of 18 (permalink) Old 02-24-2010, 08:25 PM
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Welcome to the Forums...Agree^^^^^

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post #4 of 18 (permalink) Old 02-24-2010, 08:25 PM
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Probably the cam chain tensioner.

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post #5 of 18 (permalink) Old 02-24-2010, 08:28 PM
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it's diff something to do with the timming chain..oh..and welcome to the formus :-)
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post #6 of 18 (permalink) Old 02-24-2010, 08:29 PM Thread Starter
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maybe i took screwdriver and timing chain seemed plenty tight the tensioner had to depress about half inch goin in iv decided im going to try 1 more time to fix and check out botton end make shur everything looks right new timing chain thinking about putting big bore kit on it then later turning it in to a stroker but i need to figer this out first befor i sink more money into it and the motor made alot of noise i thought it was tappets so i tried to adjust them think that may have been timing chain slapping?
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post #7 of 18 (permalink) Old 02-24-2010, 08:36 PM
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Welcome to the forums. I agree with above check timing chain.

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post #8 of 18 (permalink) Old 02-24-2010, 08:37 PM
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Originally Posted by General_Lee View Post
maybe i took screwdriver and timing chain seemed plenty tight the tensioner had to depress about half inch goin in iv decided im going to try 1 more time to fix and check out botton end make shur everything looks right new timing chain thinking about putting big bore kit on it then later turning it in to a stroker but i need to figer this out first befor i sink more money into it and the motor made alot of noise i thought it was tappets so i tried to adjust them think that may have been timing chain slapping?
did you say you put a new timming chain in ?..if you did..then something is making it jump off the timming chain upper or lower sprocket..if you changed out the upper timming chain sprocket..did you count the teeth ..and compaired it to the old one ?..if you got the wrong cam sprocket..it will get out of time real quick..which would explain why your piston hit your valves..everything has to be right..if one thing is wrong..it will cause a chain re-action to engine failure...check..double check..and when you think it might be right..check it again..make sure you got everything right..chain..tensioner..cam..rockers..adjusted the rockers when cold..check the lower timming chain gear..make sure it's the right size < teeth wise >..last but not least....look where your cam rides at the upper sprocket..see if there is any wear at all..if there is..this will cause you trouble.
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post #9 of 18 (permalink) Old 02-24-2010, 08:48 PM Thread Starter
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Quote:
Originally Posted by General_Lee View Post
maybe i took screwdriver and timing chain seemed plenty tight the tensioner had to depress about half inch goin in iv decided im going to try 1 more time to fix and check out botton end make shur everything looks right new timing chain thinking about putting big bore kit on it then later turning it in to a stroker but i need to figer this out first befor i sink more money into it and the motor made alot of noise i thought it was tappets so i tried to adjust them think that may have been timing chain slapping?
did you say you put a new timming chain in ?..if you did..then something is making it jump off the timming chain upper or lower sprocket..if you changed out the upper timming chain sprocket..did you count the teeth ..and compaired it to the old one ?..if you got the wrong cam sprocket..it will get out of time real quick..which would explain why your piston hit your valves..everything has to be right..if one thing is wrong..it will cause a chain re-action to engine failure...check..double check..and when you think it might be right..check it again..make sure you got everything right..chain..tensioner..cam..rockers..adjusted the rockers when cold..check the lower timming chain gear..make sure it's the right size < teeth wise >..last but not least....look where your cam rides at the upper sprocket..see if there is any wear at all..if there is..this will cause you trouble.
no i did not change chain was on a budget it looked fine tho the timing sprocket came off a 300 allso theyer the same
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post #10 of 18 (permalink) Old 02-24-2010, 08:53 PM
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Quote:
Originally Posted by General_Lee View Post
Quote:
Originally Posted by shadetree View Post
Quote:
Originally Posted by General_Lee View Post
maybe i took screwdriver and timing chain seemed plenty tight the tensioner had to depress about half inch goin in iv decided im going to try 1 more time to fix and check out botton end make shur everything looks right new timing chain thinking about putting big bore kit on it then later turning it in to a stroker but i need to figer this out first befor i sink more money into it and the motor made alot of noise i thought it was tappets so i tried to adjust them think that may have been timing chain slapping?
did you say you put a new timming chain in ?..if you did..then something is making it jump off the timming chain upper or lower sprocket..if you changed out the upper timming chain sprocket..did you count the teeth ..and compaired it to the old one ?..if you got the wrong cam sprocket..it will get out of time real quick..which would explain why your piston hit your valves..everything has to be right..if one thing is wrong..it will cause a chain re-action to engine failure...check..double check..and when you think it might be right..check it again..make sure you got everything right..chain..tensioner..cam..rockers..adjusted the rockers when cold..check the lower timming chain gear..make sure it's the right size < teeth wise >..last but not least....look where your cam rides at the upper sprocket..see if there is any wear at all..if there is..this will cause you trouble.
no i did not change chain was on a budget it looked fine tho the timing sprocket came off a 300 allso theyer the same
i can't say if the 300 timming chain sprocket is the same..but..i surely would get a new timming chain..maybe someone else here can tell you if the sprockets from your bike..and the 300 are the same..i don't know..but..it looks like you need a timming chain to me :-)
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