Choke removal Worth it????

[ewalker302]

Ok Ive read a lot of posts here that say removing the choke helps some.

I had my carb out the other day and I was considering doing this.

But there is such a big reduction from the carb intake where the choke is to the carb output side where the throttle butterfly is.

It just looks like to me that you could put three chokes in there and still not hamper airflow b/c of the large difference between intake & output of the carb.

In other words you still got way more room for air to flow in than out even with the choke there.

Now I dont want to ruffle any feathers, but dont give me the old less restriction=more power regardless crap.

Because the taper in the carb restricts lots more air flow than the choke.

And dont tell me its the thing to do just because you did it.

If anybody out there really knows if its worth it or not, or if somebody can get on a flow bench where they work to compare the cfm of a carb with choke and without Im sure we all would be interested.

I just dont want new guys coming here asking for advice and they get answers that equals work but no results.

:bandit:

[JOEX]

I don't know if this will help any...

The taper causes a venturri effect, increasing air velocity not resricting flow. I don't remember the "whys" of this though, just something I remember from high school autoshop some 20 years ago.....

Some one else should be able to explain it better...

Joe

[ewalker302]

Ok yeah I can see that.
The air would have to compress slightly when passing through the taper if the velocity stays the same or either increase velocity through the taper if it dose'nt compress, resulting in more oxygen, or a denser air charge either way. But regardless, this still takes place after the air flows past the choke.

But I still wonder if the flat choke makes any difference whatsoever on the flow.

Im just guessing here but I would think not since the carb output has the same charasteristics w/ the throttle butterfly being flat & on the same plane as the choke at wot.

Maybe someone knows.
:bandit:

[anywhereEx]

It does make a little bit of a diffrence on hitting the throttle you feel it a little faster. The big diffrence will come when trying to start it in the cold. 2 pumps of the throttle and it is running. Sure beats a dead battery:ermm:

[ewalker302]

Originally posted by anywhereEx
It does make a little bit of a diffrence on hitting the throttle you feel it a little faster. The big diffrence will come when trying to start it in the cold. 2 pumps of the throttle and it is running. Sure beats a dead battery:ermm:

Is that with the choke in or taken out??

I know the choke's there to help cold starts, but are you saying that with the choke in you get better throttle response?


:bandit:

[300EX_HMF]

is there another thread on how to take the choke off and do u have to take the carb completely off to do this???

[cals400ex]

there is a thread in the faq on this site. i think it has a title of "all choked up," but i am not sure. it was done on a 400ex though.

[PHIL_B54]

http://www.exriders.com/vbb/showthread.php?s=&threadid=9144

[Britt]

I removed the choke on my carb as well. I also opened up the throat of the carb while I had it out. You have to be careful how much and where you remove material inside the carb. You don't want to remove any material from the bottom of the bore or else you will begin to loose any bottom end you may have (this being a C.V. carb). I removed material on the sides (all the way to the slide and not any further so no air could get past at partial throttle) and about 1mm off of the top (but not beyond the dia of of the butterfly). I also blended everything smooth on the inlet side of the carb (again be carefull as their is not a lot of material there)

I am running a 165 main, up a clip on the needle and a 42 pilot. I want the most power while at the dunes in Oregon so i am running a little bit fat on the main because of the cool dense air and being at sea level.

A basic explanation to one of the puposes of the increase in velocity. The increase in velocity decreases the pressure in the throat (where the main jet is). This lower pressure is less than atmaspheric pressure (14.7 psi) and causes the fuel to be forced through the main jet.

Britt

[cals400ex]

britt, you said you are up a clip on the needle?? moving the clip up one notch is the same as moving the needle down one notch. this makes the bike leaner. i can't see going leaner than what the 400ex already is?? my bike seemed to run good when i moved the clip down one notch.

[kargaaro]

I was also very sceptical on what performance removing that little butterfly could do. Then I was working on it one day and decided to just remove the 2 screw that hold the butterfly to the post and I bumped the pilot up to a 45. Noticable throttle response throughout. No problems starting yet but it can be put back on in the winter if it is. Give it a test, I'm not a BSer.

[Britt]

cals400ex,

you're right! i did move the needle up (brain fart). i'm glad you caught that so no one goes the wrong way.

by the way, i did notice better throtle response and more pull after doing the mod. the thing that i noticed most (seat of the pants) was that when shifting from 3rd to 4th on dry pavement the wheels will pull up on their own. it wouldn't do that pryer to the mod. i'm running a 416, stage II cam, mild porting (just clean up), header ground, mega max II, rev kit, 14 tooth.