08 yz450 exhaust jetting help


9 replies to this topic
  • White08yz

Posted October 09, 2012 - 08:45 AM

#1



I have a 08 yz450 I put the pro circuit ti-4 full exhaust on all I did is put a 162 main jet cause I didn't want to run lean and it runs great but pops on decel can you help me out? What can I do is it normal for some popping?
I just don't want to run lean or mess the bike up it runs great besides the popping any help is appreciated

  • schrode

Posted October 09, 2012 - 08:53 AM

#2

try going up one size on the pilot

  • grayracer513

Posted October 09, 2012 - 08:56 AM

#3

Read the following:

http://www.thumperta...599#post3710599

http://www.thumperta...ad.php?t=327405

http://www.thumperta...699#post2881699

http://www.thumperta...tting-database/

  • White08yz

Posted October 09, 2012 - 08:58 AM

#4

Thanks for the reply I will try that stock is 45 so 48 would be the next size?
How do I tell if its lean just by reading the plug for the main jet anyways?

  • grayracer513

Posted October 09, 2012 - 09:20 AM

#5

Do not just go up one size without reading the links I posted. Reading the plug is a waste of time. Tells you nothing, really.

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  • White08yz

Posted October 09, 2012 - 11:09 AM

#6

Is mine a fcr carb or cv

  • White08yz

Posted October 09, 2012 - 12:15 PM

#7

And also how do I know if the main jet is lean?

  • grayracer513

Posted October 09, 2012 - 12:35 PM

#8

Is mine a fcr carb or cv


It's an FCR-MX.

And also how do I know if the main jet is lean?


Read the third link, 3-4 lines down.

  • White08yz

Posted October 09, 2012 - 05:37 PM

#9

I was messing with the bike more and when I rev it kind of high just on the stand it will shoot a flame out

  • grayracer513

Posted October 10, 2012 - 05:49 AM

#10

What happens on the stand has little or nothing to do with how it works when you ride it. A certain amount of popping on decel is normal if the bike is jetted right, as the post I linked you to first points out. But, as it also says, the popping can be caused by air leaks in the exhaust, too.

Adjust your pilot according to the second link. That will tell you whether the jet is the right size. Then, if it still pops, check the exhaust joints.





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