'05 YZ250 Summer/ Winter jetting differences?

[jim7411]

I have a '05 YZ250 with the following mods-
PC Platinum II
PC Factory Sound Silencer
Twin Air Filter
V-Force 3

I am at about 670' ASL, temps currently are in the 40's. The jetting I was running in the summer month’s was-
Main - 175
Pilot - 48
Stock needle - 2nd clip position
Airscrew - 1.5 out

Now the question. I have always jetted richer in the winter months because of the cold weather. So this last weekend before the race I decided to richen the jetting by a step which pretty much took it back to the stock jetting. I went to 178 main, 50 pilot, stock needle in the 3rd clip position, and air screw out 1.25. When I got to the race that morning I fired it up and rode it for about 3 minutes then shut it off to talk to someone. Gas started streaming out the vent hose and I could not get it started. So I took a screwdriver and tapped on the bowl until the overflow stopped but still I could not get it started. So I put a new plug in and it still wouldn't start. I decided to put the jetting back to close to the summer settings. 175 main, 48 pilot, stock needle 3rd clip 1.25 on the air screw. She fired up and I ran both motos. I got the hole shot in the first moto and took first place overall in the 40+. Seems like a great day but the bike seemed a little boggy in places. and actually choked a bit when I launched out of the gate for the second moto. Once I got the bike home I pulled the plug and it looked great.
The manual shows the jetting as being the same in the summer as it is in the winter with only two exceptions - The clip position is one richer and the air screw is in a quarter more. Is that all that is generally needed to richen the bike for the winter? I always thought that you better richen the main but the book doesn't seem to indicate this. So for you jetting guru's, what do you normally change about your jetting from summer to winter?
Also, I put a flywheel weight on the bike and this was the very first time riding it with the weight. So maybe it just felt different to me because of the weight.
Give me your thoughts on this if you would.

Thanks

 

[ryan callies]

I dont know what your bike ran like at about 70-80 degs. but I can give you an Idea of what I change my bikes from summer to winter Ice riding. On all bikes I have tuned we had them at peak power for about 75-95deg. For the winter All we changed was 1 bigger on the pilot, Raise the needle up by lowering clip 1 position, and 2 bigger on the main. That would be good for about 10-30 deg. without problems. It sounds like you just made it to rich for the small temp change. Have A good day and I hope I helped a little !

 

[Benny477]

Try the a N3EW needle(With the clip 2nd from the top),I just put that in with stock jetting 50 pilot and 178 main in my 03 and it rips.