cold weather riding/07 yz 450 f

4 replies to this topic
  • teubner

Posted January 27, 2013 - 01:04 PM


the bike runs great in warm weather ,but runs like shit in the cold hesitates 1/4 throttle im pretty sure i have to richen up the mixture( pilot jet) is that something i can do with out pulling the whole carb off ?seems like a big job if thats the case i ll just wait for the warm i hate to pull off the carb change the jet then change the jet again in a few months anyway any help will be apreciated thanx

  • Troutman

Posted January 27, 2013 - 01:19 PM


My old 06 did the same thing, very inconsistant choppy delivery from 0 - 1/4. Someone suggested disconnecting the TPS and it worked great. It took all of the hesitation out of 0 - 1/4 throttle. I also could not feel any negative effects from 1/4 to wide open after unplugging the TPS, but you may feel a very, very, slight difference in the delivery over the remainder of the throttle positions. However, if you do feel some negative effects you could always plug it back in when the air warms up. Not saying this is your issue but it is something you can try very quickly and plug back in if its not the issue.

You also don't need to remove the carb to change your main or pilot jet. Just loosen the carb air and intake boot on both sides and rotate the bottom of the carb towards you to get enough access to the float bowl drain plug. I would search the topic and read enough info on it to feel comfortable doing it this way, there is alot of info on this subject. It is easier to remove the carb and change jets but this is MUCH quicker if done gently and with the right tools.

Also, if if it is a jetting issue you may want to change the needle jet in lieu of the main or pilot, I almost remember someone suggesting a NFLQ or NFLP for the 07's lowering the clip position richer until you get the desired results. There have been lots of posts on the cold weather and the 0 - 1/8 or 1/4 throttle surging,hesitation, inconsistent delivery issue so a good search of this forum would be where I would start.

Good luck.

Edited by Troutman, January 27, 2013 - 01:57 PM.

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  • teubner

Posted January 27, 2013 - 07:17 PM


thanx for the info .im going to that indoor track in ohio this coming sunday and its going to take alot of prep time so i did not want to pull un less i had to... so i can handle loosening and rotating i may just deal with it for a while it will be warmer in the next few months. next question i have will it cause any damage with me running a little lean whats a normal temp on those bikes??? no gauges so i dont know what the bike is doing.thanx

  • Troutman

Posted January 27, 2013 - 08:18 PM


I would've definetly try unplugging the TPS first to see if that takes care of it. If it does not just simply plug it back in. If your bike is a little lean it should not hurt it, if it is very lean it can run hot and therefore have the typical issues that come with running hot which are not good for the engine over time. But like I said i would try the TPS first then re- jet if you have to.

  • teubner

Posted January 27, 2013 - 09:32 PM


i will try un plugging the tps sensor and see if that helps i know its something minor because it starts and idles fine and when i get on it .it takes off like a thanx alot 4 the help .i leave early this coming sunday i ll get back to you either way

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