MotoUtah: Motocross and Off-Road Riding in Utah

Okay jetting gurus I need some help!!

Just got my motor back together, but now I need to make sure my jetting is correct what would you guys suggest for Cedar City, and St George, on a 03 YZ250 with Pro Circut pipe and silencer?


Please help!

Alright so I think I got it figured out...

What I have found in my searching, is my bike is jetted about right, which makes since it ran good before it blew up. Now for what I have read:

"The general rule of thumb is to drop one jet size from stock per 1000' of elevation. Stock jetting is for sea level and tends to be a tad rich but it's a good reference point in situations like this."

Which stock jetting on 03 YZ250 is a 178 Main so

0' (sea level) - 178
1000' - 175
2000' - 172
3000' - 170
4000' - 168
5000' - 165
6000' - 162

Cedar is around 5800' the bike has a 162 in it....

I had a 2006 YZ 250 with a Gnarly pipe and sparky. I would detonate when really hot. Most jetting charts I've seen Honda, yamaha and KTM manual- go 2000-2550 feet or 20 degrees in tempature change to change jetting. It's always better to be a little rich and not blow it up. I ran sea level settings at Mesquite and 2 steps leaner at 4400 feet. If you run in sand you need to go richer also. I never ran anything leaner than a 172. Don't forget that the needle is most of your jetting settings-from just above idle to about 85% of full throttle. Drop the needle 2-3 and run the main 2-3 leaner from stock and go from there would be my input.
Maybe we can get a few others to give some input.

Good Luck and have fun

Thanks for the response, I am torn what to do lol some people tell me go back to stock the local yamaha dealers says 165 and other in between lol ARGHHH someone make up my mind for me lol

2nd clip,165 main.

Just checked the needle its 2nd clip so just need to pick up the main