04 yz450 still won't start

4 replies to this topic
  • Wildcard221

Posted April 07, 2012 - 12:06 AM


I checked the spark plug its getting fuel and it also has a decent spark the fuel is brand new and the carb was rebuilt and the original jet sizes that were recommended are installed and it's close but still won't start any ideas?

Edited by Wildcard221, April 07, 2012 - 12:09 AM.

  • Slow and Jerky

Posted April 07, 2012 - 05:30 AM


Have you checked your valve clearances? You may have one or more valves that are far enough out of spec to cause it not to start. I would also double check your cam timing while you are at it.

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  • Wildcard221

Posted April 07, 2012 - 09:20 AM


Do they get out of clearance that often.....and I don't think I have enough tools or the right ones to check timing and check the valves

  • Slow and Jerky

Posted April 07, 2012 - 09:52 AM


It depends on how you ride, maintenance, etc. but they do go out of spec. The cam timing is pretty simple, the cam gears have marks and so does the flywheel. It is actually easier than you might expect. If you don't have a manual you can download one here:


The hardest part is figuring out if you are "feeling" what you think you are feeling with the feeler gauge :thumbsup:

I also have found that getting a tapered set of feeler gauges helps I use a set like this:
http://www.rockymoun...on/FEELER GAUGE

If you take your time and use the manual it is not too bad, but it is important to keep everything as clean as possible, take your time and make sure to double check the cam timing with the tensioner in place. Also, I recommend taking lots of digital pictures as you disassemble so you know where everything goes when you are putting it back together. Left over parts is a bad thing :thumbsup:

  • Wildcard221

Posted April 07, 2012 - 12:34 PM


Well I bought it from a coworker...he parked it a few years ago and didn't touch it since then...but I checked the valve clearance and it turns out the intakes are at .05 and the exhaust are at .07. .......so the intake is .05 off and the exhaust is a whopping .13 off... Sooo now I just need to pull out the pads and stuff and see what their numbers are and go from there

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