2006 yz450f only runs good with choke

I acquired an 06 yz450 from a friend that passed away and I know nothing about it. It had sat for about 4 months before I got it and it fired up within about 5 kicks. Ran ok but I figured I would go through the carb to make sure everything was clean. Got it apart and cleaned it real good and blew the passages out with air and re assembled. It's got a 48 pilot jet and a 165 main. FMF mega bomb with a ti powercore muffler. Head pipe was loose when I got it Assuming everything else is stock but the issue Is it doesn't idle without the choke on and seems to run better with it on in general. The bike has fresh gas and a clean filter also. I'm not a 4 stroke guy at all my main bike is a yz250 so I'm just lost on this one. Any help would be appriacated.

Also altitude is around 800ft if that helps any

the pilot jet is very difficult to clean, you need a small needle to scrape the gunk out, or simply just replace it. if your not familiar with the jet you could think its clean,  that's the first part of the carb that gets clogged


loosen the carb clamps and twist the carb enough to get at the bowl bolts, no need to remove it completely


Sorry for your loss.

Did you leave off or crack a hose (vacuum leak)?

What's you're idle air screw set at?

I replaced the pilot jet when I had it out. So it's brand new and the fuel screw is about 1 1/2 turns out and I've played with it from about 1-2 1/2 turns out and can't get it any better. I'll look over all the lines today make sure there all attached and in good shape. Thanks


Do you run an in line fuel filter between tank and carb? Could be trash in tank clogging the pilot right after you clean it. Was there any white corrosion in the bowl? Maybe some of that broke loose and got in the pilot again. Also what about the carb air box boot seal? Is that seated correctly and the clamps tight? I have forgotten to tighten the clamp before and some dirt got in. Also be careful when removing air filter bc some chunks of dirt could fall into the boot and get suck right back into the carb. I now use the "crevice" adapter on my Shop Vac down in the boot real good when I clean my air filter.

I have had the pleasure of the same problem. I immediately did as you did and replaced the pilot and cleaned everything. The problem resurfaced after about 20 mins of riding. I went back into the carb again and amazingly the pilot was clogged up again. I cleaned it and carb again and never had another issue. Somehow there was still some crud in one of those little areas. Probably from dirt getting in the boot when I was reassembling everything.

I think it has to be the pilot.

Edited by crb357

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now