Backfireing

[250exhonda]

I have a 250ex and i jsut put on a Big Gun racing system and it keeps on backfireing. i think the carb in running to lean. what do u think.:rolleyes:

[northeast400]

sounds lean, time to rejet

Yep. Richen the main a few sizes.

[jb400exxx]

just doing the main won't get rid of backfiring alltogether. you need to adjust your needle and low speed screw too, and maybe change the pilot. you shouldn't do just the main.

The pilot should have nothing to do with backfiring. You are correct about the needle though..

[OutlawEX]

jet it or it could be bad gas:rolleyes:

[jb400exxx]

well i have heard people say that adjusting the pilot SCREW can help too. cause the backfiring is happening when you let off, where the main jet has no affect. but you will deffinetly need to change your main, and probly the needle, and turn the pilot screw out 1/4 to 1/2 a turn, or get the next size bigger pilot.

Pilot screw?:confused: Do you mean fuel screw?

[jb400exxx]

it's called the pilot screw. look in the jetting guide in ex tech. they call it a pilot screw. it adjusts low rpm.

[250exhonda]

Thanx guyz. but i no its not bad gas. i think i just have to re jett it