06' Jumped Timing/Won't Start - Yamaha YFZ450 Forum : YFZ450, YFZ450R, YFZ450X Forums
 
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post #1 of 8 (permalink) Old 12-05-2010, 04:55 PM Thread Starter
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06' Jumped Timing/Won't Start

Hey guys looking for some help on my 06' yfz. Fresh rebuild, ported head, web racing cams. Started very easy after putting it together and rode it 15-20 miles, ran great, then towards the end of the day it just dies, come to find out motor jumped timing about 3 teeth I believe. Reset the timing and bike started right up and ran perfect, just rode it around the block. Wanted to replace the timing chain before really riding any more. Replaced timing chain yesterday, bike is then doesn't want to start. Put charger on bike and got it to start, rode it for 10mins seemed down on power as when previously rode. Bike was sputtering out the carb when trying to restart. Bike started this morning, I let it just idle to heat up the oil, changed the oil and then went to restart and now nothing, won't start at all. Not really sure what has happened? Possible bent valve(s)? Just doesn't make sense that it would start right up after resetting the time the first time? Any one have any ideas?

Thanks in Advance
Kevin

06' yfz 450
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post #2 of 8 (permalink) Old 12-05-2010, 05:33 PM
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sounds like it could be the caps on the head the hold the cam journals, thosebecome tight and make the cam bind a bit causing it to jump teeth, i would check the cams without the chain on and see if they turn smoothly. just my .2 from past experiences. also check ur tensioner for proper operation.
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post #3 of 8 (permalink) Old 12-05-2010, 05:53 PM Thread Starter
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Reason for replacing the chain after the initial time jump, was because the chain was super stiff, not real sure why I didn't replace it on the rebuild. The motor turns over freely along with the cams. Tensioner is functioning properly..

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post #4 of 8 (permalink) Old 12-05-2010, 06:20 PM
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when u set time do the lobes on the cams look placed right, any chance the gear spun on the cam itself?

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post #5 of 8 (permalink) Old 12-05-2010, 06:24 PM Thread Starter
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That's another thing I was possibly thinking could of happened. But how easily can that happen? And what would cause it to spin?

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post #6 of 8 (permalink) Old 12-06-2010, 11:06 AM Thread Starter
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Anyone?

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post #7 of 8 (permalink) Old 12-06-2010, 10:42 PM Thread Starter
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Well I pulled the head tonight and have some good news and some bad news, start with the good news as being no bent valves, or piston contact, so that's a plus. Bad news being that I've found out it wasn't what I was expecting it to be, and I'm now still unsure of what my exact problem is? I also confirmed that the cam gears haven't spun and do spin freely when bolted into the head with out the chain attached..Anyone happen to have any input...?

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post #8 of 8 (permalink) Old 12-13-2010, 02:48 PM Thread Starter
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Well I got the bike back together last thursday, and seems to be running great now, so not exactly sure what the actual issue was, but just glad to have it back and going again..

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