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Discussion Starter · #1 ·
400ex Choke Removal (written by Knighttime & Lrd Mx400ex)"atvriders.com''
Description: Removing the choke plate to increase airflow. You maybe be thinking right now �How the heck will I get it started during winter time when I don�t have a choke?� Well the solution to that is 42 pilot jet, it solves the cold starting blues and you wont need the choke any more.

Purpose: A nice increase in throttle response. There is more response and most likely a little added horsepower as well. You can fell improvement all through the powerband.

Procedure

Step 1. Remove the rear fender, front fender, gas tank, air boot, and anything else that is needed to be removed to access/remove the carb.

Step 2. With the carb removed, remove the yellow choke lever. BE CAREFUL TO AVOID STRIPING THE SOFT PHILIPS SCREW!

Step 3. Now look into the carb and you will see two gold screws, remove them. WHEN REMOVING THE SCREW HOLD THE CARB UPSIDE DOWN BECAUSE THERE WILL BE SMALL METAL SHAVINGS FROM REMOVING THE SCREW, THIS WAY THEY WON�T END UP IN YOUR ENGINE!

Step 4. Remove the clip (Figure #1) and the rod that attaches to the butterfly will slide right out.

Step 5. The hole pictured in Figure #2 needs to be plugged. Put something over the hole and use a hose clamp to secure it. The hole is plugged in Figure #3.


Step 6. Put a 42 pilot in your 400 if you haven�t already done so. With the 42 pilot you will not need the choke. Just pump the throttle a few times before you hit the start button, and kind of feather the throttle at first. If you hear any popping' and cracking' or snapping sounds, it means you aren't jetted correctly.

Good luck!
 

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Discussion Starter · #3 ·
on the left side of the carb there should be a yellow leaver that moves up and down. That will be your chock. Welcome to the forums.
 

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Has anyone felt a difference with this? If it's nothing really noticeable then eh.

Changing the jets this weekend, figure if this choke mod is anything worthwhile then might do it.
 

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I would say take your chance biblical, but if you get those shavings in your engine, you will quickly see it was not worth it. Be careful removing all hardware, and even installing hardware. Do the work in a clean environment also you know what that means.. GOJO to the rescue..
 

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The most noticable difference of removing the choke plate is hard starting when cold. The only benefit of removal will be at the extreme top end of engine's rpm which is not attainable unless the rev limiter is eliminated.
 

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So it's basically not worth it. I'd trade an easier start-up over a very small percentile of power gain anyday.

Who knows, may try it in the future for an experiment.

Thanks for the info guys.
 

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There is no way this can help you in any way and also you can't just put a certain jet size in and be ok, it all depends on what type of exhaust your running, air filter, and weather or not you have stock piston. This is a very misleading thread for any of you that don't know much about engine performance!
 

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Put a 450 carb on it. big difference. But have to mod your intake boot. deffienetly worth it though
 
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