1)year/make/model- 2002 Yamaha WR250F 2)conditions (elevation,temp,humidity if extreme,type of riding)- 0-600ft elevation, 50/60 degree weather, trails/dunes 3)modifications (pipe,air box,motor)- White Bros slip-on 4)current jetting- Starter jet=72; main jet=170; Pilot jet= 48(there's a reason); Leak jet=60 5)running issue that is trying to be cured- I can't get the thing to start now. Here's the details. I had the bike near Los Angeles,CA and it ran OK; now I'm up here in Northern California with completely different conditions so I'm trying to get it running right. I had the "hanging" idle so I moved up to a 45 Pilot jet. It was still running way lean at about 4-4.5 turns out on the fuel screw (Zip Ty) , but I could still ride the bike OK with a slight bog when I'd try to wheelie in first. So about a week ago I move up to a 48 Pilot jet and the bike won't start for the life of it. I've checked the spark plug, fuel screw, jets, etc... And to make it worse I still have the compression start which is very frustrating when trying to start the bike while the jetting is off. One thing I have noticed though (don't know what causes this) is when I'm holding in the compression lever and just kicking the bike over, the exhaust seems to "flush out" more. It shoots out exhaust fumes and makes a loud "POP". To lean still? And I tried going back down to the 45 PJ but still cant get it to start.