jetting for 426 for the cold


4 replies to this topic
  • 2001YZF426Rider

Posted March 17, 2008 - 08:14 PM

#1

I studded my old dirt tires, and i started my bike today and it didnt want to start after sitting for a couple months or so.. I finally got it going, but it was sputtering and popping like crazy.. I dont want to take it out on the lake riding like that.. Do i have to jet down or up? Up i would say right? What do you guys recommend? Just change the mains? For temps between say 20 degrees and 40 degrees..

  • grayracer513

Posted March 17, 2008 - 08:32 PM

#2

Cold temperatures need richer jetting. Rule of thumb is one step up in size for each 15 degree drop. A "step" would be like a 42 to a 45, or a 45 to a 48 on the pilot, and a 165 to a 168, or a 168 to a 170 for the main. The pilot and main should be all that is necessary to change.

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  • Dustin_Mabro

Posted March 18, 2008 - 05:46 AM

#3

you say it sat for a couple months, could the carb need cleaning or some fresh gas?

  • BASSic

Posted March 18, 2008 - 08:35 AM

#4

I studded my old dirt tires, and i started my bike today and it didnt want to start after sitting for a couple months or so.. I finally got it going, but it was sputtering and popping like crazy..


Cold temps will affect your jetting somewhat, but it shouldn't necessarily be 'sputtering and popping like crazy.' Before you alter jets, clean your carb and try some fresh gasoline.

I bought a used YZ426 recently that had stock jetting. The previous owner had it in storage last fall and winter without riding it. It didn't want to stay running, but after draining and refilling with fresh gas it was fine. I've been riding the bike in 20-30 degree weather on stock jetting and it runs great. It's probably not optimal jetting, but I don't have any complaints. I'm installing a JD jet kit this weekend, so we'll see if that changes my opinion.

  • 2001YZF426Rider

Posted March 18, 2008 - 08:47 AM

#5

I probably will clean the carb, it usually runs mint.. It probably is just bad gas.. When i converted it to sm, right before it sat, it ran fine in the cold..

Once it warmed up, it was fine, it didnt sputter or anything, so maybe it was a little gummed up, but i will take it apart and clean it..





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