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jumpinjerryk426f

2000 YZ426F Problem -- Please Help

8 posts in this topic

The problem started as the throttle is snapped the engine coughs then powers up. When the throttle is rolled on it the power is all there!! :cry: Just when you need a quick snap it dies b4 accelerating. Does it at half throttle also. :lol:

I cleaned the carb. Twice, air filter is clean, tried to adj. the air screw and put in a new plug. I even changed the accelerator pump. No change in problem. :D

The new accelerator pump parts listing did not specify difference in the 4 different ones available, so the parts guy said order the first p/n, it should be the original one anyway. :cry: The new one came in with the number 3.7 on it. The one I took out of my bike is a 4.3. The throttle response was better but still has the snap cough. :D The parts guy wouldn't refund me the part for exchange for the 4.3. :cry:

Tonight when I started it, it was hard to start. It took about 3 kicks for it to fire off then die. Did it about 7 times. :D I got it to stay running by giving it some gas. It sounded like crap then. :cry: It ran, popped and backfired repeating in that order as long as I kept some gas to it. The eng. RPM was erratic but would not idle. :lol:

What's wrong?? :cry:

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On my 02 426 I cliped the A/P spring off at the bend on the cam side and rebent it this made the pump spring a little stonger. Then you will need to do the BK mod so you can adjust the duration of your A/P. do this and I promise you won't be sorry. Also you may need to bump up your pilot jet one size. If you need more info PM me.

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sounds like its running lean - had the temp changed quite a bit

you might try to adjust your needle in the carb down (I believe) a notch and then get you an adjustable air screw like a (ZipTy)

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Do a search for the BK mod and get a Zipty fuel screw (or other brand extended unit).

The jetting is way off on the 2000 model. On mine, I did the BK mod and JD jetting kit. Then adjusted the fuel screw and there was no bog.

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I went to the track the day after my post and the popping and backfireing quit. :cry: The temp. was up about 25 deg. It ran real good except for the snap bog. :cry: I had plenty of power. Enough to have no problem landing the 100 ft. tabletop. :cry: I had to deal with the snap bog when taking 90 deg turns trying to snap out of them. :cry:

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I went to the track the day after my post and the popping and backfireing quit. :cry: The temp. was up about 25 deg. It ran real good except for the snap bog. :cry: I had plenty of power. Enough to have no problem landing the 100 ft. tabletop. :cry: I had to deal with the snap bog when taking 90 deg turns trying to snap out of them. :cry:

The Bog is a known issue in the 2000 two things you can do

1: get the 2001 Needle, this will clean up the mid snap

2: the GB mod is a must on the 2000 follow this Link GBMod

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