02 yz426f won't start(popping noice)

5 replies to this topic
  • ewd199

Posted February 25, 2010 - 01:41 PM


I have an 2002 yz426f and I recently have not been able to get it started. I went out to start it just like I always do, choke on and I give it about three quarters throttle to prime it (live in PA so its been cold) and it usually starts right up. I went out and it started fine but then shut off after about 3 seconds (always does, usually have to kick twice). So I went to give it another kick, and another, and another, and then there was a loud quick pop almost what I thought was a back fire. I have been around dirt bikes for 10 years and never had expierenced this before. I went to kick it a few more times and I heard the same noise. I thought I may have flooded it so I just left it alone for a day. Went to start it again today and it won't even fire once. I know a little bit more then just the basics about engines and stuff, but this particular problem I am stumped. Please give me any advice you have. Thanks

Edited by ewd199, February 25, 2010 - 02:04 PM.


Posted February 25, 2010 - 04:50 PM


I know my 426 is very hard to start when its cold (live in pa also), also it does backfire sometimes when I try to start it in the winter, summer runs perfect.
If you ride in the winter I would rejet but I only really start mine up every once and a while to run it, so I don't mess with it.

Also I have had a problem with gas going bad very quickly this year, I have had the carb off more then once and found it gummed up even with fuel stabilizer in it.

  • spc mike

Posted February 25, 2010 - 06:31 PM


Definitly check that pilot jet. I just pulled my 02' 426 out for a ride this past weekend from two months of non-op and it had those exact symptoms, so i pulled the carb and sure enough the pilot jet was gummed up.I cleaned the carb throughout and it fired right up on the first kick.

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  • JandJ07

Posted February 25, 2010 - 07:16 PM


I had a problem exactly as you are describing when I first got my 426. After about 50 kicks and fully exhausted I gave in for the day. After resting the first place I turned was the spark plug...it was a little wet, but didn't seem too bad. I replaced it anyway and it fired first kick and has been great since. It may be as simple as that. Spark plugs aren't often the problem on four strokes, but when they go...THEY GO. Good luck.

  • onearmbandit

Posted February 25, 2010 - 10:21 PM


I had a similar problem to this once upon a time on my YZ400. After a bit trial and error I finally took the accelerator pump apart and what I found was that the spring behind the diaphram had broken. The bike would try to start but after the initial spurt of gas there was nothing putting pressure on the diaphram and therefore no gas getting into the mix(At least this was my assumption because it would try to start but couldnt). Every once in a while it would pop instead of run for 3 seconds or so. Once i replaced the spring, it started right up and idled fine.

I am not saying this is your issue, but I would definately take the little accerator pump apart and see how things look in there.

Also while you have the carb off, make sure your pilot jet didnt suck up anything. Take it out and blow some air/carb cleaner through it.

Since you now have the pilot jet out, blow some carb cleaner through the passage you took it out of. You should see the fluid come out of the hole at the other end of the passage.

Those are the things I would check first

  • ewd199

Posted February 27, 2010 - 06:06 PM


yo thanks guys, i took in to consideration all your tips and my bike runs like new! thanks again

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