Bigger starter jet?


7 replies to this topic
  • yz400fdude

Posted April 05, 2009 - 10:28 AM

#1

My '07 yz450f almost always takes at least 5-6 hard kicks to get it started and I'm getting a sick of it. My '98 yz400f would always start first or second kick for me so why is this thing so hard to start? The valves are within spec and all the jets are clean. I also put in a brand new spark plug. Should I try a bigger starter jet? If so what size should I try? What size is the stock starter jet?

  • William1

Posted April 05, 2009 - 12:36 PM

#2

If once the bike starts, it stays idling with the choke on, the starter jet is fine. Try giving the throttle a few quick twists just before you kick it.

  • TIG88

Posted April 05, 2009 - 01:17 PM

#3

If once the bike starts, it stays idling with the choke on, the starter jet is fine. Try giving the throttle a few quick twists just before you kick it.


+1. I usually twist the throttle 3 times before starting, 5 times if its been more than a week or 2.

  • yz400fdude

Posted April 05, 2009 - 02:12 PM

#4

+1. I usually twist the throttle 3 times before starting, 5 times if its been more than a week or 2.


It seems to idle kinda low with the choke on, but it does stay running without a problem. I ride the bike at least once a week so it is not like it sits a long time. I'll try priming it with the throttle like you all do and see if it helps. I usually turn the fuel on, wait about a minute and twist the throttle once, then start kicking. I will try 5 twists on the throttle this time :thumbsup: Thanks for the tips

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  • grayracer513

Posted April 05, 2009 - 07:50 PM

#5

One thing to ask here is how cold the weather is currently? Very cold weather can cause difficult starting unless a lot of extra fuel is introduced via the accelerator pump.

If, when you cold start with the choke, the bike idles for more than 45 seconds without starting to "blubber" from being too rich, the starter jet may be too small. If the bike doesn't start first or second kick when you give it a couple twists on the throttle, but will start sooner if you give it a couple of twists before each kick, that could be another indication.

Most '06 and later 450's were like this, especially compared with the earlier 400' and 426's. Overall, it works out better, as it make them less prone to flood, especially in warm weather, but it can take a little getting used to.

  • yz400fdude

Posted April 05, 2009 - 09:04 PM

#6

One thing to ask here is how cold the weather is currently? Very cold weather can cause difficult starting unless a lot of extra fuel is introduced via the accelerator pump.

If, when you cold start with the choke, the bike idles for more than 45 seconds without starting to "blubber" from being too rich, the starter jet may be too small. If the bike doesn't start first or second kick when you give it a couple twists on the throttle, but will start sooner if you give it a couple of twists before each kick, that could be another indication.

Most '06 and later 450's were like this, especially compared with the earlier 400' and 426's. Overall, it works out better, as it make them less prone to flood, especially in warm weather, but it can take a little getting used to.


I gave it 5 twists of the throttle today before I started kicking and it still took 4 kicks for it to start. It was about 45 degrees out today so it wasn't real cold, and it would idle for 10 minutes with the choke on if I let it. It doesn't get rich with the choke on. I guess it wouldn't hurt to try a bigger starter jet. In the jetting forum I saw that a lot of people were using a #72. I'm going to have to take my starter jet out of my bike and see what is in it. I'm pretty sure it will be the stock size but I have no idea what stock was.

EDIT: I found out that the stock starter jet is a #72. Maybe I should try a #74?

  • grayracer513

Posted April 05, 2009 - 09:32 PM

#7

45, my good fellow, is "real cold", I don't care who you are. The starter jet will probably help, but you'll want to change it out when the warmer days come.

You could try priming it (twisting the throttle) each of the first 3-4 kicks, and if it hasn't started, try either cracking the throttle open barely off idle, or using the hot start with the choke.

  • yz400fdude

Posted April 06, 2009 - 07:05 AM

#8

45, my good fellow, is "real cold", I don't care who you are. The starter jet will probably help, but you'll want to change it out when the warmer days come.

You could try priming it (twisting the throttle) each of the first 3-4 kicks, and if it hasn't started, try either cracking the throttle open barely off idle, or using the hot start with the choke.


I was going to change the starter jet tomorrow but it is suppose to be about 62 degrees. Should I see how it starts in 60 degree weather first? It's going to be warming up in the next couple weeks so if I will have to change the starter jet again I don't really see the point, but it might be a good idea for me to know for next winter.





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