Posts
3
Joined
5/21/2023
Location
Tinley Park, IL
US
Edited Date/Time
5/27/2023 2:28pm
Hey fellas,
I recently installed the Athena Big Bore 290 kit on my 2003 yz250f. Also added stage 2 cams. From what I’ve heard the bigger piston siphons more gas through the carb now. I’m not sure how to rejet the bike properly. I’ve downsized the main jet to 170 but everything else is standard. Pilot 42 and I’m not sure about the rest. I believe my bike is still running rich. Was hoping you guys could offer some input into what size jets I should have. My elevation is typically around 650-700. I’m from Chicago so this summer I’ll be riding around in about 75-100 degree heat. Thanks for your time and advice.
-forgot to add recently I’ve been bogging out when I attempt to pop a wheelie in first. The power is extremely delayed
Check the plug and it should tell lean or rich
I remember we used to go leaner on the pilot on those kits. Go down one size at a time until it starts backfiring when you chop the throttle. Once it does then see if you can add fuel with the fuel screw. If that doesn't fix go one up from that point and you should be good. I think I was about 168 MJ.
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