Carb issue


4 replies to this topic
  • Lahi671

Posted April 10, 2012 - 07:48 AM

#1

Hi, All

I am new posting here. But, I have been reading on this site alot for tips. Anyways, I got a 2000 YZ426f on a trade. It strated up fine after i change the spark plug within three cranks. I saw it was spitting out oil between the exhust manifold and the headers. I read on here that if it does that it's running rich or it's missing the gasket. So i bought a new gasket and the JD jetting kit for the bike. Now, After I installed the kit and the gasket the bike will not start....

I took the pilot jet out and sprayed it with some carb cleaner. Did the same with whole carb… BUT, when I cleaned the whole carb, I sprayed the valve seal that sits on the plate. It got brittle and some cracked off. So, it’s not sealing properly. You think that’s the cause for not starting up?

It's the one that goes around this plate in the picture. How important is the seal on the plate and what is the main purpose?


Things I check and confrimed;

There is fuel coming in… I drain refilled.

I used the JD fuel screw with the old spring, washer and O-ring it that same order

The AP squirts out gas.

There is spark.

The plate is on correctly. with the hole facing towards the needle
Posted Image

Edited by Lahi671, April 10, 2012 - 09:47 AM.


  • grayracer513

Posted April 10, 2012 - 10:10 AM

#2

I saw it was spitting out oil between the exhust manifold and the headers. I read on here that if it does that it's running rich or it's missing the gasket.


The part about it running rich is inaccurate for a 4-stroke.

After I installed the kit and the gasket the bike will not start....


I would consider that a "clue".

...when I cleaned the whole carb, I sprayed the valve seal that sits on the plate. It got brittle and some cracked off. So, it’s not sealing properly. You think that’s the cause for not starting up?


The four strokes have a very strong vacuum against the slide on the intake stroke, and with flat slide carbs, this has a tendency to momentarily bind the slide to the carb body. Obviously, this raises concerns about the throttle closing correctly on demand. To counter this, Keihin first installed rollers on the slide to reduce the drag. Then, since there must be an effective air seal between the slide and the carb body, the vacuum release plate was added to the engine side as a floating element. If the seal in the release plate fails, it will affect starting and low speed performance, and the proper trim of the idle circuit is of paramount importance to the 426 if you want them to start reliably. So start by correcting that and see where it goes.

I'm not a fan of jet kits in general, but you can see how it works out once you get the seal replaced. Ballpark setting on the pilot screw should be 1 3/4 to 2 turns out.

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  • Lahi671

Posted April 10, 2012 - 01:25 PM

#3

Okay, I order the plate seal it should arrive this week...I will see if that fixes the starting issue.

  • Lahi671

Posted April 17, 2012 - 08:02 PM

#4

Update; I replace the vavle seal and the bike still won't start. It pops/backfires... What could it be? Took out the spark plug and it still looks new. I am out of ideas. Any help will be much appreciated.

  • Lahi671

Posted April 20, 2012 - 01:13 PM

#5

okay, it wa the fuel mixture screw. JD jetting sent the wrong one, And installed it and only had three turns to it. tried a diffrent brand and it started right up.





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