Jetting in in AZ

7 replies to this topic
  • Guest_mxrider426_*

Posted June 18, 2002 - 07:32 PM


Is there anyone that lives in the Phoenix area of AZ? If so, what jetting do you run? The guy at the shop has the same bike and he says that I shouldn't have to change it from stock. But I think I need to adjust something. The bike is stock, it is just below 2000ft, 100+ degrees, and very VERY dry. Are these changes enough to have to rejet?(I am new at jetting 4 strokes)

  • mat

Posted June 18, 2002 - 08:12 PM


on my 99 i just went up one on the pilot here in vegas

  • YZ400Court

Posted June 19, 2002 - 05:37 AM


I'm not sure what stock was but I go one richer on the main, needle clip and pilot from these settings. I found these settings on a website 3 years ago. I am running a Big Gun competition pipe with spark arrester.

YZ400, aftermarket header & silencer @ sea level:
1. 180 main jet
2. #52 pilot jet
3. "DP" needle, 4th position from top
4. 2 3/4 turns out on Fuel Screw

I have a 98 YZ400 with 426 piston. It says "DP" needle, but I have the stock one.

  • Tim

Posted June 19, 2002 - 06:26 AM


I was in Phoenix in Feb (a far cry from summer temps), but I ran the same jetting as in Illinois.... I usually run a little richer than stock to keep the popping to a minumum on decel, but I was a little rich for the area. Stock jetting should be about perfect.....Unless you really want to fine tune the carb for your riding style.

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  • F624ZY20

Posted June 19, 2002 - 08:56 AM


Check my jetting below. This is after the BK mod. I still feel I now that it is hot I could go richer. What part of the RPM are you having trouble in?

  • yznvegas

Posted June 19, 2002 - 09:11 PM


My bike is running factory jetting. I live in Vegas so our altitude and ambient air temp and humidity are about the same. My bike runs just fine and starts fine, doesn't fould plugs etc.

Remember, the jetting that comes from the factory is perfect for sea level and about 75 degrees. (southern cal. weather). Well, that puts us here in the hot and dry desert to run a little rich.

yz400court wrote: YZ400, aftermarket header & silencer @ sea level:
1. 180 main jet
2. #52 pilot jet
3. "DP" needle, 4th position from top
4. 2 3/4 turns out on Fuel Screw

yznvegas: If you are 2 3/4 out on the fuel screw than you should go up a size on the pilot because with the screw that far out you risk losing it. It could vibrate out.

  • Guest_mxrider426_*

Posted June 19, 2002 - 09:24 PM


I was having trouble with the top end. I don't know if it was rich or what, but it just felt like it didn' want to be pinned in 5th. It usually makes a nice rolling noise, but it made a whinny noise.

  • yznvegas

Posted June 19, 2002 - 09:29 PM


Try a size leaner on the main jet and see what happens. If the only problem is when the bike is pinned than don't even worry about the needle position or the pilot. Good luck.

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