grayracer513 I need your help again

I have posted this on the jetting section, I have done countless searches and I am more confussed than ever.

I have a 07 YZ450F with Dr.D exhaust and the JD jet kit and I am having lots of problems. I started off with JD recommendations 170M 48P blue needle 4th clip from top and 1 1/4 turns on fuel screw. That was bad, The bike was very hard to start and ran very rough. Then JD told me to go to 45P 170M red Needle 5th clip from top and 1 1/4 turns. The bike starts better but while riding and holding throttle at 1/8 to 1/4 no matter what gear the bike sputters and on decel it back fires like a bitch. :)

My conditions are as follows. 70°F 1200' 93 octane.

I want to go back to stock jetting parts, Where should I be on the jetting?

Thanks in advance for your help!

Stock would be 45/165 (usually)/NFLR in #4.

A lot of people seem fond of a 48/165 or 168/#4 combo.

I have posted this on the jetting section, I have done countless searches and I am more confussed than ever.

I have a 07 YZ450F with Dr.D exhaust and the JD jet kit and I am having lots of problems. I started off with JD recommendations 170M 48P blue needle 4th clip from top and 1 1/4 turns on fuel screw. That was bad, The bike was very hard to start and ran very rough. Then JD told me to go to 45P 170M red Needle 5th clip from top and 1 1/4 turns. The bike starts better but while riding and holding throttle at 1/8 to 1/4 no matter what gear the bike sputters and on decel it back fires like a bitch. :)

My conditions are as follows. 70°F 1200' 93 octane.

I want to go back to stock jetting parts, Where should I be on the jetting?

Thanks in advance for your help!

this set up from JD is for temps below 60.....

Use the red needle and 165/168 mj

1 1.5 turns - 2.0 turns out for temps above 70. Once you get it right the power will be sweet as JDs needles are what you paid for....kit works well but you need to test with diff jet combos

this set up from JD is for temps below 60.....

Use the red needle and 165/168 mj

1 1.5 turns - 2.0 turns out for temps above 70. Once you get it right the power will be sweet as JDs needles are what you paid for....kit works well but you need to test with diff jet combos

What clip possition should I use?

What clip possition should I use?

3rd or 4th - try both of these

I have the same pipe as you but I dont have the jd jet kit. My jetting is

165 main

48 pilot

clip in the #4 pos and the fuel screw at 1 and 3/4 turns out and the bike is flawless, no popping or hesitations just pure raw power.

The main stock on the 07 450 is a 160!

That depends on how and where it was delivered. YZ450's are shipped with 3 main jets. The '06 comes with a 160, a 165, and 170. "Stock" jetting is either what's published in the manual, or what you found screwed into the carb when you started messing with it. The dealer will often tweak the jetting with one from the kit to make it suit the area he sells in. The listed standard MJ for an '07 is in fact a 160, though.

I have posted this on the jetting section, I have done countless searches and I am more confussed than ever.

I have a 07 YZ450F with Dr.D exhaust and the JD jet kit and I am having lots of problems. I started off with JD recommendations 170M 48P blue needle 4th clip from top and 1 1/4 turns on fuel screw. That was bad, The bike was very hard to start and ran very rough. Then JD told me to go to 45P 170M red Needle 5th clip from top and 1 1/4 turns. The bike starts better but while riding and holding throttle at 1/8 to 1/4 no matter what gear the bike sputters and on decel it back fires like a bitch. :)

My conditions are as follows. 70°F 1200' 93 octane.

I want to go back to stock jetting parts, Where should I be on the jetting?

Thanks in advance for your help!

If your bike still sputters at steady throttle, use 1 clip position leaner on the Red marked needle. The deceleration popping can sometimes be improved by richening the fuel screw, but an exhaust leak will cause decel popping too.

If the starting becomes more difficult when the bike is hot, your idle mixture is too rich, and the fuel screw should go back inwards. Sometimes deceleration popping results with perfect jetting, so don't focus entirely on rejetting for it. Make sure the pipe is sealed at all the junctions too.

Thanks,

James

That depends on how and where it was delivered. YZ450's are shipped with 3 main jets. The '06 comes with a 160, a 165, and 170. "Stock" jetting is either what's published in the manual, or what you found screwed into the carb when you started messing with it. The dealer will often tweak the jetting with one from the kit to make it suit the area he sells in. The listed standard MJ for an '07 is in fact a 160, though.

Pennsylvania delivered 07 450 will have a 160 stock,along with a 165 and a 155 option.I know in higher altitudes the dealer should drop atleast 2 down on the main,but I doubt it.:)

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