Fuel Screw

I know this sounds dumb... but i've been a 2-stroke guy for the 4 years ive been tinkering with dirtbikes. But i recently got an 00' Yz426 and put a WR silencer on it due to the lower noise level and spark arrestor.

The bike isnt fouling spark plugs at all... but i know the jetting could stand to be a little leaner for better throttle response. Where is the fuel screw? Is it the same thing as the idle screw? I am usually pretty good with working on engines, but i dont have an owner's manual....

On 2-strokes its right on the side of the carb, but this thumper carb is much more complicated. So any help is appreciated. If someone has a picture, or could just describe where it is then that would be great. Thanks :)

The 426 doesn't have a fuel screw, it has an air screw. It is located on the very bottom of your carb and recessed. You can adjust it with a short screw driver and a small mirror. Contrary to what you may hear, you adjust it just like you would a fuel screw. Just go in until it idles rough, go out until the it idles rough again, then put it back in the middle. If your pilot is the right size you will end up around 2 turns out....

This screw on the FCR carb is actually referred to as the Pilot screw. Many also do refer to it as a "fuel screw". The results of turning this screw are opposite of what they are on a 2-stroke carbs "air screw". Turning in = leaner, out = richer.

hmmm I'm not sure if you're right or not dad, I'm too lazy right now to go out in the shop and look in the manual but I am sure about the adjusting part. I knew I would get some argue about that but now that I think about it you might be right about the richer/leaner part. That would be good info if he had to re-jet.

MikeOK, apologies if I sounded like I was arguing. I did check the manual before I posted just to be sure. Your advice on adjusting was good. I was just trying to add some useful info.

2 strokes use an air screw.

4 strokes use a FUEL screw.

OUT is MORE fuel & IN is LESS, like Dad said.

I knew about the fuel screw thing, and know how to jet... but i just had no idea where the darn thing was! lol... thanks for the info, i did finally find it.

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