Winter yz jetting

Mx391
Posts
202
Joined
10/25/2017
Location
Mid, TN US
11/7/2018 8:34pm
I've got a completely stock 18 yz250 with stock jetting. Starting to get a little chilly here in TN. What jets should I change to account for the lower temps?
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kb228
Posts
6089
Joined
1/31/2018
Location
Mansfield, OH US
11/8/2018 5:19am
what jets you need to change is entirely dependant on how far your throttle is open when you have issues.

That being said youll need richer jetting for colder weather. You might get away with adjusting your clip position and adjusting the air screw
1
barnett468
Posts
1239
Joined
7/19/2018
Location
Wildomar, CA US
11/8/2018 7:28am
In general, if the bike is properly jetted for one particular ambient temp, the main jet does not to be changed unless there is a difference of at least around 30 degrees in ambient temp providing there is not a significant change in the elevation it is being ridden at.
1
pete24
Posts
2661
Joined
10/20/2011
Location
Marlborough, MA US
11/8/2018 7:44am
the last yz250 I had was a 16 so should be the same as yours, I ran stock jetting from 45 degrees to 90 degrees here in new England, straight race gas 32:1 with spectro sx premix
1

The Shop

Pirate421
Posts
1709
Joined
7/26/2015
Location
MA US
11/11/2018 3:29pm
I rode today in NH and my jetting was really good. 0-1500ft
38* degrees F
Pilot 50
Needle N3EW 2nd clip
Main 180
Talisker
Posts
831
Joined
10/25/2018
Location
Houston, TX US
11/13/2018 12:51am
Run it then check it. Sometimes the cold weather (depending on how cold) will clean up the jetting and make it perfect.
11/13/2018 6:44pm
Where do you live in mid tn? I live in Dickson!

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