2000 yz426 won't respond to throttle


5 replies to this topic
  • 5point9

Posted September 28, 2013 - 02:32 AM

#1

Hi all..

 

Recently bought a 2000 yz426, relatively clean bike, but not perfect. Stock exhaust, previous owner put a 450 carb on it with the hot start lever.

 

First 4-5 times I rode it, it ran fine. Throttle response, power, was all perfect. Fun bike.

 

The other day, I went out to start it to ride in the woods behind me. First or second kick it started as normal. When I went to shut the choke off it died. It's never done that before. Usually I can shut the choke off instantly and start riding! Like I said, before it carburated perfectly!!

 

Restarted, did the same thing. 

 

Restarted and noted some things. WIth the choke on, it will stay running but will not respond to throttle. If I shut the choke off it will either die or won't respond to throttle and die. It's like the throttle is a kill switch.

 

Pulled the carb apart and clean the jets, as I've read on the internet that this is a classic symptom of a plugged pilot jet. Everything in the carb looked clean. While the pilot jet hole seemed small to me (I couldn't fit a small staple through it) it didn't appear to be clogged. 

 

Put everything back together. Same thing, started 1 or 2 kicks on choke, sounded ok, but would literally die if I gave it any gas or shut the choke off.

 

Wierd, cause this literally happened as the bike sat! Ran perfect when I shut it off. Runs like crap when I restarted it.

 

Changed the plug.. color looked good, maybe a tad rich or dark but not that bad.

 

Other thoughts? Supposedly the guy before me adjusted the valve recently. Motor sounds tight.

 

Thanks all!


Should add that I looked pretty hard for misc air leaks as well, I don't see any. 



  • Thommo_400f

Posted September 28, 2013 - 02:39 AM

#2

Could be pilot jet passage or Pilot air jet blocked.

  • 5point9

Posted September 28, 2013 - 03:05 AM

#3

Yeah, that's what it sounds like for sure. I guess I will pull everything back apart again. Maybe I'll buy a new pilot jet while I am at at.

 

Makes some sense, as I ran it out of fuel and my friend gave me a little gas from his 1905 dirty old gas can, wonder if some crud came out of that can? 

 

Any other thoughts people? Anything mechanical I should be worried about? Again, ran fine when I shut it off. Horrible when I restarted.

 

Literally any throttle input is a death sentence and stall. Seems like she ain't getting fuel.


Also, I looked around for air leaks.. nothing that I could see.



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  • 5point9

Posted September 28, 2013 - 03:10 AM

#4

Also, dumb question, but is there any way to remove carb without removing the throttle cables from the handlebar? Seems kinda silly to me that you have to do that but maybe I am missing something?



  • 5point9

Posted September 28, 2013 - 05:13 PM

#5

Ok, found the problem. Interesting.. I sat down and thought about what the "timeline" was for the issue. It was exactly when I added new fuel from a local "Speedway" gas station. I opened the gas tank and smelled the gas. It smelled very weak, odd. Sure enough, I drained the fuel both from the tank and the float bowl, filled it with "fresh" gas and she ran like a champ IMMEDIATELY!!! Amazing, I would of never of thought that I would get bunk gas from a station, but that fuel smelled rank and weak. I am going back there tomorrow and asking if they had issues!

 

She runs perfect now. What a waste of time doing all this work for nothing! Argh!



  • rogo1

Posted October 01, 2013 - 02:47 AM

#6

fwiw I always just pull the cables at the carb. makes life alil easier







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