Mixture Screw Falling Out Of 06

I have an 06 YZ 450 and just took it out for the first time this weekend. Well no more than 15 minutes into my ride the mixture screw fell out of my carb and my bike ran like crap. Well i really wanted to go riding so i borrowed the mixture screw out of my friends 05. Turned it 2 turns out as per the manuel says and again like 5 minuties into my ride it fell out again. The screw is under tension with the spring so i cant understand why it keeps falling out. Anyone else have this problem?

Did you lose the little o-ring and washer?

The bigger question is did you lose the spring the first time it fell out. I lost mine without knowing it when I switched to a Zip-tye fuel screw. Didnt notice until later when my mixture kept changing on me. check to make sure you have o-ring, washer and spring.

Mine fell out also. It was about 2 turns out. But I was really, really lucky. Like lotto lucky. I allready had a zip-ty I was contemplating putting in, but I was dragging my feet because of the few people here that complained of it falling out. So I decided to just use a home made t-handled screw driver to adjust the stock fuel screw.

I went to ride it about a month ago and made some adjustments because it was so cold. Rode it, parked it then went to ride it again and it started hard and back fired like crazy and repeatedly stalled. So I went to adjust the fuel screw and to my horror it was gone! My buddy and I went back to the spot in the drive way where it was parked just to go through the motions of looking. We actually found the screw, washer and O-ring but couldn't find the spring. Damn! I was still screwed. My buddy who had been neeling on the ground looking got up and looked down to see the spring he had been neeling on. It was slightly bent but I mostly straightend it out and used the parts on the zip-ty.

8 rides later and it hasn't ever moved from the spot I adjust it to for that day.

Here's the fix, your mixture screws will never fall out again. And you'll still be able to adjust the mixture.

If you're careful, you can drill the hole without taking the carb or bowl off. Drill the hole low enough that you'll still have room to move the screw 3 or 4 turns out. Put the screw in and then put the safety wire through the hole. If you drilled it in the right spot, the side of the screw will just touch the safety wire. If the screw does loosen, the machined flange (where the spring sits) on the screw will hit the wire and it won't be able to fall out.

I've done this on the last few FCR's I've had and never had a problem.


The fuel screw will fall out for sure if you don't have the oring and the little washer in place n top of the spring. See Burned on how to jet it. I took his mainjet and air screw (forgot the numbers now) and it fixed me right up. No more popping and starts when you open the kick lever!

If it has the o-ring, the washer, and the spring, it won't drop out. One of these 3 parts must either have been defective or missing. You need an extended screw anyway, though, and the good ones come with the new parts.

If it has the o-ring, the washer, and the spring, it won't drop out. One of these 3 parts must either have been defective or missing. You need an extended screw anyway, though, and the good ones come with the new parts.

You're right gray, if all the pieces are there it shouldn't fall out. The biggest reason is guys turning the screw out too far trying to fix a lean pilot problem. Most of the time it's on brand new bikes though, I think the nice new screw and threads sometimes makes it too easy for it to turn and unscrew. Once the bike has a few hours on it the chances of it unscrewing are far less just because everything gets a little sticky.

I did the safety wire thing on my new bike just to be safe, I didn't really need to.

BTW, I ordered a Vortex ignition for my '06, I'll let you know how it works out. I talked to Mike Tolle down at MT racing for quite a bit about it, he seems like he knows what he's talking about. The soft delivery of the '06 might be a good candidate for something like the Vortex box. We'll see.

Let me know too, because that is next component I will use. Thalk to you soon. :thumbsup:

Yeah, talk about torture, I just picked up the Vortex, and it's going to be an awesome weekend for riding, too bad I'll be in Chicago for the next 4 days! :thumbsup:

I'll let you know how it works, I'm riding the following weekend or else. Like I said, I think it might be a good thing on the '06, I think it would have been a waste of money on the '03. If the soft power delivery is mostly (I'm sure not all) in the timing, this should wake it up. I know some of the guys here with a lot of dyno experience aren't too hot on the Vortex, but I can see two reasons for that.

First is HP differences show up fine on a dyno, but power delivery differences are a little harder to see. Especially 1/8 or 1/4 throttle response, which is where the timing map differences should show up the most. Kinda like big core pipes, they may show higher peak HP on a dyno, but when you're actually in the dirt the response just isn't there. And I'm not expecting any peak HP/ WOT differences, that's not what I bought it for.

The other reason is not all bikes would benefit from a different timing map, like the '03 YZ450. Unless you wanted to tone it down, then it would probably be great. If someone bought the Vortex for one of those bikes and put it on the dyno expecting more HP, they might be dissapointed. I'm betting the CRF's are probably timed pretty good stock, not sure the Vortex would give much to those motors either. I dunno. I'll find out for myself next weekend, I just wish it was this weekend.

just put a little blue locktite on the screw and it stays tacky enough that it won't vibrate loose and can still be adjusted

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