03 YZ450F Cold start problem


7 replies to this topic
  • birdmanmt

Posted August 26, 2015 - 10:35 AM

#1

Hi guys,

 

New to the forum and dirtbikes. I picked up a good deal on the bike in the subject a few weeks ago. 

 

It has started and ran perfectly for maybe a dozen rides, it came from a friend who was very anal and has a very good maintenance history. 

 

Yesterday, I started it and let it warm up, but forgot to turn the choke off. While i was putting my helmet and gloves on, it died and wouldn't restart.

 

I have read through a bunch of threads on carb adjustments etc, but I see no reason to dive into that just yet as it was running great. I put a new spark plug in this morning just for giggles, but no change.

 

Where would you start? I am aware of the proper start procedure for these bikes and have been following it.

 

Thanks for your time.

-Jeff



  • grayracer513

Posted August 26, 2015 - 01:13 PM

#2

The only "procedure" that needs to be followed is to avoid opening the throttle (very far) and to find the hard spot that indicates the start of the compression stroke, reset the kick crank back to the top and kick.

 

"Very far" refers to the fact that there are quite a few '03's and '04's that seem to like the throttle cracked just very slightly off idle when starting cold.  The one I owned cold started best on 2-4 twists of throttle to prime the engine, then open the slide just a tiny bit and kick.  Usually twice or less.



  • birdmanmt

Posted August 26, 2015 - 06:57 PM

#3

The only "procedure" that needs to be followed is to avoid opening the throttle (very far) and to find the hard spot that indicates the start of the compression stroke, reset the kick crank back to the top and kick.

 

"Very far" refers to the fact that there are quite a few '03's and '04's that seem to like the throttle cracked just very slightly off idle when starting cold.  The one I owned cold started best on 2-4 twists of throttle to prime the engine, then open the slide just a tiny bit and kick.  Usually twice or less.

 

Thanks for the reply, that's how this one was until yesterday. The plug I had as a replacement was a couple steps cooler, so I went and got the right plug at the dealer. Try that tomorrow.



  • birdmanmt

Posted August 27, 2015 - 08:40 AM

#4

Looks like the plug was it, back to its normal self this morning with a new plug. Off to the mountains!



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  • birdmanmt

Posted August 27, 2015 - 09:35 AM

#5

Well that was fun, made it two miles into the NF and it died running about 60mph in 4th. Won't restart/fire. Talk about frustrating, although i'm getting to know neighbors for rides home...



  • grayracer513

Posted August 27, 2015 - 10:09 AM

#6

If it died underway, it may have stored a fault code that will help run the problem down.  Sounds a bit like a fuel pump.



  • birdmanmt

Posted August 27, 2015 - 10:51 AM

#7

If it died underway, it may have stored a fault code that will help run the problem down.  Sounds a bit like a fuel pump.

 

It's an 03 carby.



  • grayracer513

Posted August 27, 2015 - 12:22 PM

#8

Why yes it is, isn't it?  Got crossed up with another similar thread.

 

Check the stator as described in the manual.  If you don't have one, look on the second post in the Common Threads pinned topic.  There are links to free downloads from Yamaha.







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