09 Yzf450 bogging out upon starting

4 replies to this topic
  • darknesss

Posted June 02, 2009 - 08:49 AM


Hello, my yz450 has recently become difficult to start. I kick the bike over, and it will run for a few seconds, then stall. I tried increasing the idle, and it allows the bike time to warm up then i turn it back down, and sometimes when i give it some throttle it will stall (wont start at all with some choke). Perhaps its an issue with my jetting? Never had the problem when i first got the bike a couple of months ago. Also the bike has sat for 2 weeks, maybe this is the problem? Some help would be greatly appreciated.

  • Justin89

Posted June 02, 2009 - 09:20 AM


BY an aftermarket fuel mixture screw and start there...sounds like your a little on the rich side to me:thumbsup:

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  • clutchless

Posted June 02, 2009 - 09:21 AM


I would suspect the warming of the temps in your area are the issue. 2 months ago the air was cooler and a bit more dry, now it's warmer with more humidity.

play with the fuel screw a bit. Stock is 1.5 turns but go to 2.5 turns out and see what that does.

if not check the jetting database and see what people are running in your area or a climate and altitude that are close to where you are at.

  • KtmKramer

Posted June 02, 2009 - 02:18 PM


Warmer temps equals richer mixture. Go in on the fuel screw to lean it, not out. Unless you're running certain race fuels, sitting for a cpl wks won't harm anything.

  • Wiz636

Posted June 02, 2009 - 03:39 PM


Like others have said, if sounds like you are a little bit rich on the pilot circuit (you said it will not start with the choke, right?) You can probably help it by turning in your fuel screw a full turn but we haven't even hit summer yet so temps are going to continue increasing...probably best to replace the pilot jet with the next leaner size.

I would suggest reading this:

and get an easily-adjustable fuel screw and do this:

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