Newbee on YZF400 - won't idle off choke

30 replies to this topic
  • grayracer513

Posted November 16, 2011 - 12:20 PM


Odds are that it's not the seat causing the problem, and there's nothing you cab do to to refinish the needle itself. Your only hope is that it's dirty or dried out. Soak the needle in gasoline overnight, then reassemble it and see what happens.

You also need to inspect and check the adjustment on that fuel screw. Having the pilot clear will do little good if the fuel can't get past the screw. You can't say you've cleaned the carb thoroughly unless you do that.

  • eflyguy

Posted November 16, 2011 - 01:38 PM


I pulled that fuel screw out and cleaned the needle and port. The tip did have a little build-up on it. I also had cleaned the float needle previously to make sure there was no debris preventing it from sealing, but no-go - fuel is leaking past it when I test as you described. Tried several times. Something else - I noticed the part that the needle slides in was out-of-round - the needle, which is squared off, can't actually rotate in the part, and could easily get hung-up if it sat in the wrong position.

So it's good I've ordered that whole set. I just hope it gets here on Friday so I can ride this weekend..

Edited by eflyguy, November 16, 2011 - 03:43 PM.

  • eflyguy

Posted November 19, 2011 - 04:52 AM


Part didn't come in. Guess I'm riding my wife's new XT250 tomorrow!

  • eflyguy

Posted November 19, 2011 - 12:58 PM



Fixed it! Figured it out all by myself!

First, I found that a T40 bit was the perfect size to get the brass assembly back in round. I dropped it into a socket, and put the bit in a driver, and forced it around until there was no resistance. After cleaning it out, the needle now moved without resistance.

Reassembled but left the bowl off, hooked up gas, and it still leaked. Thing is, it didn't look like it was leaking from around the needle.

Pulled it apart and that's when I realized what was supposed to be an O ring around the brass assembly was now a dried up strip that was doing nothing! Took it to Home Depot, found an O-ring that fit, and put it back together. SUCCESS! No leaks!

So it's running like a champ now and, most importantly, it idles great even at much lower RPM than spec (which I know isn't good for it - just checking that the jet issue was resolved)..

COOL! So I take my bike to the mountain tomorrow. First time on dirt in 30 years. Wish me luck!

  • eflyguy

Posted November 20, 2011 - 07:28 PM


How many times can I post in my own thread?

Rode today.
Oh. My. God. What a blast!

Bike ran GREAT, way more capable than I could ever hope to utilize but can certainly handle everything I will every throw at it.
Posted Image
Posted Image

Started on second kick this morning, and idled perfectly (the original problem I posted about.)

Couple of videos from my day:


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  • RasmusDK

Posted November 21, 2011 - 03:58 PM


Great you got it right! Good videos (what a trail! wish i had access to those!) You bike pops some on decel. if you want that gone and smoother throttle, get a 08 carb for it =) made huge diff on mine and it sounded just like that with my old carb.

  • eflyguy

Posted November 21, 2011 - 04:20 PM


Thx. I don't mind the pop and after the time I've invested I will just run what I have.

  • RasmusDK

Posted November 21, 2011 - 04:26 PM


Gotya. It sure is great bike poping or not :-) cheers

  • eflyguy

Posted December 06, 2011 - 03:56 AM


I'm going to be pulling the carb off again to replace the needle valve assembly (I ordered the whole kit), new float valve seal as well.

So, while I'm messing with it:

Talking about the popping on decel, would any kind of adjustment reduce that? I find if I have just the slightest pressure on the throttle, the popping goes away. That means the popping is from it being a little too rich on idle, right? Do I want to mess with the mixture screw?


(side note - we ride around the property most evenings as my wife and daughter are still learning and like to get saddle time, so I pull mine out to ride with them. Using "the technique", it's is starting on the first kick most times, and even that doesn't have to be a hard kick. Awesome!)

  • grayracer513

Posted December 06, 2011 - 07:27 AM


Talking about the popping on decel, would any kind of adjustment reduce that? I find if I have just the slightest pressure on the throttle, the popping goes away. That means the popping is from it being a little too rich on idle, right? Do I want to mess with the mixture screw?



  • eflyguy

Posted December 06, 2011 - 07:46 AM


Awesome. I'd read that before but forgotten. So is it worth messing with the fuel screw? If you've watched any of my video (i.e. - at 1:40 or so) and heard it, is that just normal?

Doesn't bother me - just wondered if I should do something about it while I'm messing with the carb again.

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