2001 yzf 426 starts but then dies after a couple seconds?


20 replies to this topic
  • dbmstr124

Posted November 03, 2008 - 01:31 PM

#1

have a 2001 yzf426. I bought it and it ran pretty good for a couple times out...Recently I let it sit a couple months and then it was very hard to start, and ran very hot, and would only run and idle when it was choked...I just re-shimmed the valves hoping that would help, they were off a bit...I was just kicking it and I can get it to fire when choked...run a couple seconds and the second I barely touch the throttle it dies...Carb problem? If so where do I start? I tried adjusting the throttle stop screw....just guess and check then kick it...not sure which way to go or if its the problem....thanks for your help...oh yeah its got a new plug and filter....thanks again.

  • ktm113mcp

Posted November 03, 2008 - 01:40 PM

#2

My dads EXC 400 did sorta like that and also a had a XR that did something similiar after setting for awhile. The XR had a stopped up main jet and once I saw it I was suprised it ran at all also may have old gas. The 400 when first cranked it wont run without choke and any throttle kills it, then you can keep popping th clutch to make it pull out of its tracks but it still don't run right, it also has been running very hot but not really sure if it has to do with it. Still not sure about the 400 but it sounds similiar. But my guess is yours is probably in the carb. i would start with fresh gas then check jets.

  • dbmstr124

Posted November 03, 2008 - 01:49 PM

#3

Thank you...I'll check the gas and then probably pull the carb off and do a visual inspection of it to see where to go from there...Thanks...

  • dbmstr124

Posted November 03, 2008 - 02:08 PM

#4

one more thing...some one said that the clutch may be bogging down the engine and that I should check that? What do you think? Sticking plates or something?

  • ktm113mcp

Posted November 03, 2008 - 03:25 PM

#5

I haven't really ever heard of that, and I don't think if the clutch was to stick it would effect it in that way, but from what you describing I would say it would be in the carb or valves and my bet would be the carb. Also I noticed you live in NC, with it starting to get cold, 4 strokes can get tempermental especialy if they don't have just the right jetting. I have been wrong before but I would rule out the clutch.

  • jmodc919

Posted November 03, 2008 - 03:33 PM

#6

speaking from identical issue experience its a clogged main jet clean it out and youre good to go.........

  • dbmstr124

Posted November 03, 2008 - 05:13 PM

#7

I really do appreciate your responses...I am definately pulling the carb and looking forward to having my bike back....thanks again.

  • dbmstr124

Posted November 04, 2008 - 07:26 AM

#8

alright well I pulled the lower half of the carb off and...well it looks pretty clean...I have to questions though....I took pictures and there is a hole in my carb that doesn't look "normal" is it supposed to be there...and also the jet I pulled out have the picture of me holding it and where it goes...I couldn't blow through...is that enough to cause problems? Thanks..
well I don't know how to add the pics, but the jet is the pilot jet I believe...the longer one with the tiny holes at one end...it goes down next to the main jet...thanks again...guess I'll have to figure out how to show that hole.

  • grayracer513

Posted November 04, 2008 - 07:41 AM

#9

If you don't have a manual, download one at:

http://www.yamaha-mo...ice/manuals.jsp

  • ktm113mcp

Posted November 04, 2008 - 07:47 AM

#10

I cant really see it in my head, but I once had a piece of trash in my carb about the size of uhhh, a piece of lent from your belly button j/k and it made my bike run horrible. anyways you get the point a little trash goes along way, I would clean out or get a new one and stick it back together. One of your jets controls how much fuel is applied during idle and I want to say its the main jet, but I could be Bass Ackwards, how was the gas?

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  • dbmstr124

Posted November 04, 2008 - 07:48 AM

#11

Thank you...I'm borrowing my buddies. The manual pictures don't show the corner of the carb where I think the suspected hole is...and dont' say if that jet should be blown through...but I did get it opened up so I can...guessing that was a problem...but is that little tiny hole a big enough deal to cause my symptoms? Thanks for your help...any idea how to upload pictures with photobucket now lol

  • ktm113mcp

Posted November 04, 2008 - 08:55 AM

#12

any thing is big enough to cause a problem.lol but really it could be at least part of the problem, as far as pictures Im still new to so your guess is as good as mine I m guessing its under ''Go Advanced" under the type box then just copy and paste might work

  • grayracer513

Posted November 04, 2008 - 09:10 AM

#13

One of your jets controls how much fuel is applied during idle and I want to say its the main jet, but I could be Bass Ackwards, how was the gas?

It's backwards. The pilot jet meters fuel at idle. That jet is located forward of the main jet, and has a very small orifice in it. A simple layer of fuel varnish will cause the problems you are having, and you won't be able to see it, necessarily. Push a fine piece of wire through the jet to clear it.

Also check the air jets in the face of the carb, and the pilot screw and seat.

  • ktm113mcp

Posted November 04, 2008 - 09:16 AM

#14

Thank you grayracer I couldn't remember to save my life. another question while I'm being schooled, What causes the varnish?

  • grayracer513

Posted November 04, 2008 - 09:22 AM

#15

...What causes the varnish?

Varnish is what gets left behind as the volatile elements of the fuel evaporate. These deposits often take a while to accumulate, and not everything that composes "varnish" necessarily came from the fuel to start with. It can include components of dirt and other stuff that get dissolved into the fuel. It is also sometimes called "fuel lacquer", or "shellac".

  • dbmstr124

Posted November 04, 2008 - 09:27 AM

#16

The gas isn't bad...I cleaned it out and put it back together and now not even a fire...could have flooded who knows...I'm gonna let it sit and go from there...I adjusted my air/fuel screw back to stock. 1 1/4 turns out...maybe that doesn't work at sea level...guess its all up in the air right now. The carb looked really clean and I pulled out the main jet and could blow right through it...I'm stumped...I'll probably go back in and check my shims on the valves, make sure they are correct and I didn't have a brain fart...it feels like my bike has a bit more compression on the kick after the shims, seems like it should...I dropped my exhaust shim from a 1.75 to a 1.65 because they were out at .152 and spec is .25-.30...

  • ktm113mcp

Posted November 05, 2008 - 11:05 AM

#17

thats a litttle odd bud, never even fired up? have you already started checking valves?

  • dbmstr124

Posted November 06, 2008 - 08:53 AM

#18

Yes I took off the head but haven't had time to work on it...shift work kicks me in the butt....I'm thinking I'll re-check all them and go back into the carb...I didn't know that that little bit of clogging would do it...Thanks

  • dbmstr124

Posted November 11, 2008 - 04:03 PM

#19

So I re-shimmed the valves and I was off a little bit, but they're good now...Still just fires though, doesn't want to run...I just pulled the carb apart and I have some questions...So I pulled off the accelerator pump diaphram and next to it is another small rubber seal...guessing the gas comes in here? I'm not really sure how this thing works...inside the bowl of the carb there is little almost ball looking thing that goes down...and the back side is a brass piece and that matches up to this diaphram...sorry for the bad explanation....It seems that this should move down and allow fuel into the accelerator pump possibly? I can't push this down at all...therefore I cant get the brass piece out at the bottom? Is that bad? Also my buddy said something about needing to drill out a tiny lead or brass piece in these carbs and get a screw in it so you can pull it off? Anyone have any ideas? Thanks

  • dbmstr124

Posted November 11, 2008 - 04:07 PM

#20

Here are the pictures...I think, lets see if it works





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