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Discussion Starter #1
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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did you replace timming chain ?..sounds like your timming chain is streched too far..which caused it to jump time
 

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Welcome to the Forums...Agree^^^^^

Do you know 300ex powered by monster?
 

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Probably the cam chain tensioner.
 

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it's diff something to do with the timming chain..oh..and welcome to the formus :)
 

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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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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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Discussion Starter #9
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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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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Discussion Starter #11
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 :)
thank you just trying to get ideas beofr i ruin anouther head and piston set
 

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your welcome..check it all real good..before you put it back together..better to do it right..instead of wasting time and money, and if you don't have a repair manual..i reccomend that you purchase one for your bike :)
 

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Discussion Starter #13
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 :)
my bad it was a 300ex sprocket came with other motor i got with 4 wheeler
 

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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 :)
my bad it was a 300ex sprocket came with other motor i got with 4 wheeler
get a new timming chain..a timming cam chain upper sprocket..check everything out before you put it back together...check your cam..cam rockers.
 

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timing chain

I've got 1997 Honda 300 ex I put new timing chain on but not sure I've got it in timing. It won't start I went ahead put new spark plug to. I need help please.
 

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I've got 1997 Honda 300 ex I put new timing chain on but not sure I've got it in timing. It won't start I went ahead put new spark plug to. I need help please.
i'll try to help..but keep in mind...i don't know much about sport bikes ..as in..your model ?..lol..but the basics are the same bro. left hand side..remove the inpsection caps from the side of the motor..one is your crank bolt ( the large center )..the other is smaller..has a slot like a screw driver in it..remove that. now..remove your valve cover ( the whole rocker box ! )..now..take the spark plug out..from left hand side..with a 17mm socket and ratchet..turn the crank around..one way or the other ..sorry..i do not know which way yours turns for this ?..i know how they turn for mine..but not yours !..i'm gonna guess..and say it also turns clock wise ??..as your turning the crank..watch inside the smaller inspection hole..your looking for the T mark to come around on the edge of the flywheel ?...when it shows up..line it up with the line thats inside the case..now your on TDC..( this is top dead center by the way ). now you want to make sure your piston is on TDC on the compression stroke ????..to do this..turn the crank bolt ( 17mm )..counter clock wise..as your doing this ?..watch the intake valve..it should start to move as your turning the crank ????..if it does ?..then turn the crank back clockwise..all the way abck to where that T mark lines back up..now your on TDC on the compression stroke !. if for some reason..when you first set the T mark up to begin with..and you turned the flywheel back counter clockwise ..and the intake valve DID not move ???..then you had it set at TDC on the exhaust stroke !!..which means..you need to turn the crank 180 degee's...one full revalution in order to get that T mark back to the line in the case in that small hole !. ok..now that you got it all where it needs to be ?..lol..look at your cam sprocket ..there is two punch marks..or lines..stamped on both outter sides of the cam sprocket..these marks should be horizonal to the head's surface ?????..if they are not..then your cam is out of whack. one good way to see this..is when you get those lines on the cam sprocket where they should be ?..look at your cam..the lobes should be facing straight down..once every thing is lined up right ?!.
 

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Got my 300 running thanks for the help. Now have 4 more Wheelers I want to tackle. So look out!! Thanks again!!!
your welcome..glad you got it going !.
 
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