Starting problems

[Mock1]

I have a yamaha YZ426F and am having problems starting it. I had this problem about a week ago and found it to be a fouled park plug, so I went and changed it and started right up, and everytime after that. Now it seems the problem is back, starts for a sec and then cuts, I kick and kick but nothing. Could the new plug be fouled out this soon or is there another problem that is causing this? Any suggestions would be great! thanks

 

[jpsYZF]

Mock1,

Only a guess here at this point, but since no one else has answered, here goes... Assuming that you've owned the bike for some time and this problem has just started occurring, it's possible that your running way too rich (like as if choke was still on), and when it conks out basically your flooding it when trying to re-starting. Simple stuff first; Do you have a clean air filter (not over oiled) and fresh gas? Try another plug (cr9e), but this time start the bike and run it up to normal operating temp (don't just let it idle, ride it), then pull and inspect the plug closely. It should not be wet or have a uniform black carbon deposit. If it does then your running way too rich, which can foul a plug very quick. There are many possibilities as to why it could be running too rich.... incorrect carb float level due to sticky float valve, bad float valve seal, or simply a dirty or gummed carb from old gas or lack of use.

If you don't find the help you need here, check out thumpertalk. They have a specific forum for other WR400_426_450's riders. A quick search there for "starting problems" found over 250 threads for these 3 bike types. Example thread:
"Re: Starting Problems WR426F, advice needed: Long story short the problem seemed to stem from a number of issues, perhaps all caused by old gas and oil seeping from the filter. After everything was cleaned out, with new gas and plug installed everything is good. Thanks for all the tips, very helpfull."

Let me know how things worked out.

jpsYZF