Why would my 98 TRX300 idle best with the fuel mixture screw turned all the way in?


The story: Sat 6 months. Wouldn't start. Disassembled and cleaned carb. Junk in fuel tank clogged some jets. Installed a fuel filter & reinstalled everything. Idle screw set at stock 2 turns out. Started right up & ran fine. I only rode about 10 min. Three hours later, wouldn't start. Smelled like it was getting fuel. Spark was fine. Removed spark plug and found it wet with fuel. Cleaned plug, reinstalled. Started right up and throttled fine. Went to adjust fuel mix screw and found out that it idles best with the screw turned all the way in.


What causes this? How is fuel getting past the mix screw? Could it be something with the choke?

 

Clean your carb again
You have a plugged jet

 

Wouldn't a clogged jet cause it to already be lean and turning the screw in makes it even leaner?

 

Could have worn jet or someone cleaned jets out with drill bits or something hard an oversized low speed jet its common for people to clean jet out with torch jet cleaning files an most the time oversize hole in jet..

 

Jet needle could also be worn from an bad air filter in it past an sand blasted jet needle[ brass needle] Try cleaning carb an install an repair kit...make sure repair kit had all hardware[jets and needle]

 

Aw man. I think you're right. I got too lazy to strip some copper wire. So, I used the tools for my welder to poke through the jets. I guess I'd better order new jets. Wouldn't closing that screw all the way shut of fuel all the way?

 

Hold it, your choke can stick slightly open, this is quite common, it can be the cable but is often the plunger in the carb or the spring on top got water in and rusted away, the little rubber sealing ring can swell and stick too. It is worth checking that the choke is working right before new jets. I never use anything but compressed air and never move the idler mixture screw when cleaning carbs, only had one jet that wouldn't clear with air in over 100 rebuilds, I fitted a new jet on that one.

 

That old of a bike, order the rebuild kit, they are only about $25.

 

Thanks Merryman I will check that before I replace the jets. Does the choke increase fuel, decrease air, or do both?

 

01ssreda4, this is a new-ish carb. I replaced it last year because I hadn't run it in years and no matter how much I cleaned the old carb, it wouldn't run right.