YZ125 jetting question for DEEP sand track/cool temps

Which track we talking here? Even at the Dunes I went up one size on my 500 in the cooler weather, and Yamahas are usually jetted pretty spot on.

I'd bring a couple extras with you, and go up one on the main tonight. My guess is it will be soggy down there, so it will definitely load the motor hard. You'll know pretty quickly if one was enough, is there lots of room to change the jet on that bike? As in take out the drain plug and get the 6 mil socket up in there? It rained like a son of a bitch down here yesterday at times, going to be nasty down there.

I'd second Scooter's advice and go up one on the main. Cold temps = denser air, so you need to go richer anyway. The sand will put lots of load on the engine so you want to be extra careful. Check the plug after practice and if there's any hint of white, raise the needle too.