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BergArabia

YZ perfection

6 posts in this topic

It is getting kind of hot here.

As in never gets below 80 degrees fahrenheit.

Frequently over 110 degrees F.

That is the bad news.

The good news is, the bike has never run so well.

Starting literally first kick every time. Even after sitting for a week..

Even after cleaning the air filter with water and soap and adding filter foam and not letting it dry out completely.

In the winter is is a little harder to start.

So it is perfect for summer but next winter what should I do?

I mean, does this mean it is a touch lean for winter?

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Get a J/D jetting kit. It comes with two needles, that are designed to be used for Hotter/less dense air, and a needle that works for Colder/more dense air. They are marked "red" and a "blue" needle respectively. The kit also comes with (I think) 4 different Main jets.

I run the "Blue" needle when it goes below about 70 or 65 degrees (Fahrenheit), and the "Red" needle above 70 degrees. The "Red" needle basically leans out the lower half of the throttle range.

You will also get better throttle response with the J/D kit (versus stock), since J/D customizes the needle shape for your particular bike's throttle mapping. I really like mine on my 2004 Yz450f.

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Get a J/D jetting kit. It comes with two needles, that are designed to be used for Hotter/less dense air, and a needle that works for Colder/more dense air. They are marked "red" and a "blue" needle respectively. The kit also comes with (I think) 4 different Main jets.

I run the "Blue" needle when it goes below about 70 or 65 degrees (Fahrenheit), and the "Red" needle above 70 degrees. The "Red" needle basically leans out the lower half of the throttle range.

You will also get better throttle response with the J/D kit (versus stock), since J/D customizes the needle shape for your particular bike's throttle mapping. I really like mine on my 2004 Yz450f.

Thanks Flintlock.. :thumbsup:

I guess it is time for me to start learning about jetting and stuff.

All I have been doing with the bike is cleaning it, changing the oil, cleaning the filters and waxing the chain and it has been great for 2 years. Kind of idiot proof..

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Yep, this site will cause you to become more proficient at taking care of your bike, and learning more about it. I was nowhere up to speed about Carbuerator's until reading up on them here on TT.

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does this mean it is a touch lean for winter?
Yep, that's what it means. 30 degrees drop in temps means the jet should be increased to 1.03 of the previous size. A 160, for example, should be replaced by a 165. The pilot should also go up one size, but the needle position won't necessarily need to be changed.

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gray is right.....the reason I suggested the J/D kit, is that it gives you more options for really getting the jetting dialed in. I think my 04' yz450f kit came with 4 jets (160, 165, 168, and 170) and two needles (Red and Blue) along with an extra c-clip. I left the Blue needle in the bike all last year and it ran fine. This year, I decided to put the Red needle in since the temperature's are now over 70 degrees, and it's recommended. The bike ran great this Memorial day, but I had to keep the fuel screw turned out about three turns. This means the red needle is running a tad lean, and I'm going to go up to a larger Pilot jet to compensate.

Don't feel intimidated about jetting, once you start learning the ropes, it gets to be relatively easy.

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