New 04 to me Dr D Exhaust jetting problem maybe

5 replies to this topic
  • martman100

Posted March 29, 2010 - 01:25 PM


Okay I am new to the bike world but I recently bought an 04 YZ450 and I don't think the jetting is right due to the popping it has on mid throttle acceleration the tremendous amount on deceleration. A good friend who knows a bit about them thinks the same. I know they pop some on dec. but nothing like this.

It has a 165 main jet and I believe that is stock. I looked at the jetting thread but I got more confused since it looked like a lot of people were running a 158 main with after market pipes and I have never heard of down sizing a main with an after market pipe.

I am in KY so 0 1500 ft altitude should work.

Nothing aftermarket except a twin air air filter. I have not checked the plug color yet but doesn't a 165 seem on the small side. Not sure on the pilot yet either will check it tonight.

What would you all suggest in regards to the DrD SS from a pilot/main standpoint?

If you think the current jetting is okay then what else would I need to look at.


  • grayracer513

Posted March 29, 2010 - 01:42 PM


You know that the main jet has not one thing to do with decel popping, right?

Either your exhaust leaks, or your pilot is lean.



  • martman100

Posted March 29, 2010 - 04:49 PM


Thanks for the links for sure. I knew the main wasn't the issue with the decel popping I just got in a hurry and didn't clarify that.

So 165 sounds right? I am going to check the pilot size and also go over the exhaust I wanted to confirm the main first.

In addition to that I need to check the af screw. I would suspect from reading the other posts that 1.5 to 2.5 would be the "normal" range and outside of that is another indicator.

I will go through the carb as well since the guy I got it from said he has only ridden it maybe 4 or 5 times since 06. Means it has done a lot of sitting.

Thanks again for the links. I don't know how you all find this stuff so easy. I search substantially before I post any questions on these forums.

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  • grayracer513

Posted March 29, 2010 - 05:58 PM


I don't know how you all find this stuff so easy. I search substantially before I post any questions on these forums.

"Common Threads: Look here 1st! Mods, Maintenance, Common Issues and FAQ's "

Top of the index.

  • martman100

Posted March 30, 2010 - 03:23 AM


I read that section and that is where the confusion set in. Since I seen posts that said people with 04s were running 158 main when they come stock with a 165 according to the service manual.

I come from the yfz450 atv world and they have to substantially have the main jet changed for a pipe and a bump up on the pilot circuit as well.

I will get it dialed in thanks for the help.

  • grayracer513

Posted March 30, 2010 - 08:45 AM


My point was, in response to your surprise at my being able to find "all this stuff", that all of what I linked you to is posted in Common Threads.

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