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usaf_yz426

426 wierd starting problem

19 posts in this topic

i am having some weird issue's starting my 426. It will not start unless i have the hot start and choke levers pulled at the same time. but once it starts i can push the hot start lever back in and it will idle with the choke on. but once i push the choke back in after it is warmed up, it dies. it seems weird i would have to pull both levers out to start it. any idea's.

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Yes, your jets are plugged. Both fuel and air. Take it all apart and blow air through it, re assemble making sure all passages are clear.

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i will give that a try, i took the bowl off and there was no tarnish in there. so i assumed the jets were good to go.

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Hey I know this post is a few days old...have you got it fixed yet. I have seen a condition similar to yours when the A/F adjust screw in the bottom of the carb had vibrated all the way out. Just an idea to check.

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the little orifices on the side of the pilot jet were a little clogged up. i'll let you know when i get her back together tonight.

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well, i thuroughly cleaned the carb. and checked my valve clearance. and i still have to pull the hot start and choke to get it started, then once its started ill turn off the hot start and it will idle with the choke on. but once i turn the choke off, it dies. i am wondering if jetting is the issue now. but it was running perfect 5 months ago.i am at my witts end.

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Do you still have the decompression lever on it? I wonder if the cable is too tight and it may be opening slightly.Just a shot in the dark.(I'm the king of shots in the dark.Mostly because I have no actual knowledge,although I have been told that I have the brain of a mighty T-REX!)

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negatron, i have the hotcams with the autodecomp loab. and yes the timing is spot on. and for good measure, i changed the spark plug. i have a 45 pilot jet. but whats got me frazzled is why it starts with the hot start and choke on. don't they kinda contradict eachother?

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well i have verified that my valves aren't stretched. i am coming to a conclusion that the problem is jetting, but i haven't messed with the jets at all.

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it's just an idea, but i am sure my bike's muffler is long overdue for repacking. do you think this can cause it to lean out and run like crap?

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I dont think your muffler has anthing to do with it, but if it needs it then it should be done. Did you just clean the jet? The pilot circuit could be clogged too. Take out your fuel screw and spay from the throat of the carb down. You will see the little hole in the intake side of the slide. You should probly take your carb off to do this. And take out the pilot jet too when you do it

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"Idles with the choke on, won't idle with it off"

That's a pilot circuit problem, plain and simple.

  • Obstructed jets or passageways, including the discharge port
  • Pilot screw too tight/not adjusted properly
  • Pilot screw O-ring missing or damgaged
  • Pilot screw missing
  • Throttle slide vacuum plate damaged or installed upside down

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I've been very, very happy with my 426. Been firing up on the 1st kick this last week.

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i cleaned the carb thuroughly. the o-ring, spring and washer are on the fuel screw. the throttle plate is in serviceble condition and is installed correctly. and the fuel screw is in the same exact position it was in when it last ran correctly.

but my question is, how come it only starts when i have the hot start and the choke levers pulled. it will not start on the choke, but it will idle "ok".

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but my question is, how come it only starts when i have the hot start and the choke levers pulled. it will not start on the choke, but it will idle "ok".

With the pilot circuit not functioning, there is no fuel delivery without the "choke" (not truly a choke) on. The is also no air blended with the fuel as there is in the functional pilot circuit, so the hot start (or cracking the throttle partially) is necessary.

Be certain you inspect the air jets in the mouth of the carb.

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well, i got it to run. i didn't have my idle adj. screw out enough. now it starts right up, and idle's without the choke on. so i took it for a spin, wow i forgot how much power this thing has. makes my drz-sm feel like a mo-ped.

p.s. i double checked my pilot circut works,i almost got sprayed in the face by being complacent.

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well, i got it to run. i didn't have my idle adj. screw out enough. now it starts right up, and idle's without the choke on. so i took it for a spin, wow i forgot how much power this thing has. makes my drz-sm feel like a mo-ped.

p.s. i double checked my pilot circut works,i almost got sprayed in the face by being complacent.

Good to hear.:thumbsup: Now get out there and tear some sh!t up...:lol:

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