I have an 01 TRX 90 with stock bore/stroke and stock carb and jets. Its sputtering on anything past 50% throttle, until I COMPLETELY remove the air fuel screw. The farther I back out the throttle screw, the better it continues to run until it's completely removed. Revs fine with the air/fuel screw in up to 50%, problem is only on the top end power. Any ideas/help?

 

Sounds like you may need a carb kit. No way you should have to remove this screw to make it run properly.Dirt Cheap Honda & Arctic Cat OEM Parts & Accessories – Cycle Parts Outlet http://www.ebay.com/itm/Honda-TRX90-2001-2002-2003-2004-Carb-Carburetor-kit-/191059575261?pt=Motors_ATV_Parts_Accessories&hash=item2c7c09c1dd&vxp=mtr

 

Thanks for the links. I can get the thing running perfectly with the air/fuel screw in on the bottom and mid, just not the top. It leads me to believe its the needle, needle jet, or the main. I just wish I had a smaller main to try out.