I need to know how to adjust my jet setting on my AC 250 2x4. I have never been into a carb like this. From what I have gathered from other posts, I can make some minor changes in the jetting, without physically changing the jet. I figured once I got into the carb I would see how this works. I removed the brass plate and diaphram from the top of the carb. From here I removed the two screws that hold the gray piece that slides into the carb. ( the screws were a pain to get out I guess it takes a special tool. I made one by drilling a hole in a torx bit). Here's where I am stuck....Does this gray piece slide out?? Is that the jet at the bottom of it? I have not been able to get it out. I am thinking that once I get this piece out, there will be an adjustment on the bottom of it. Can anyone tell me if I am on the right track? Would I be better off taking it to a dealer? Thanks

 

First off your at the wrong end of the Carb. All the jets are at the bottom. Pulling out the gray piece should be your slide that moves up and down in the venture (throat) of the carb. Now You cannot make adjustments without replacing jets, needles, or slides. Excpet for for Idle adjustment and or idle set screw. Before you make any adjustments you need to figure out what your quad isn't doing to decide if and what adjustments need to be made. Start by cleaning your air filter, and installing a new plug with the correct gap. Get the motor up to operating tempurature. Each component controls a different part of the throttle range. from idle to 1/4 throttle is controlled by the idle set screw and the pilot jet. from 1/4 to 3/4 is controlled by the pilot Jet, and from 3/4 to full is controlled by the main jet. Each of the jets have a number on them the higher the number the richer the setting the lower the number the leaner the setting.

 

ttaylor,
Thanks for the reply.....I've seen other posts where they comment about setting the needle to slot 4 or slot 2, like there is an adjustment there. As far as which side of the carb to go into, yes I was in the throat of the carb. I basically just took my seat off, and the air filter off and removed the brass plate that was right there on top. Do I need to take the carb out totally or can I get to it from the bottom? It's pretty tight in there. PS the symptoms I am seeing are that the quad won't run at open throttle when its cold outside ( previous post on 12/19 AC 250 cold-natured.)

 

That sounds like you need to get a larger main jet. You can get one for less than 5 bucks.

 

Newbie69,
If your quad is sputtering and back firing at full throttle then it is your main jet that needs to be replaced. You don't need to remove the carb. Just loosen the clamps so you can twist the bottom of the carb out. At the very center in the bottom is a plug. take off the plug and directly above the plug is the main jet. Take it out and look at the number. To go richer get the next number higher. To go leaner go the next number lower. Make sure you only jump one number at a time. If your sputtering, this means you are too lean so go higher on the main jet. Sitting next to the main jet is the pilot jet. It is smaller than the main. For the neddle adjustment, start counting the grooves from the bottom up. Don't make adjustments unless you are having trouble. The higher the groove the leaner the setting. The lower the groove the richer the setting. The needle controls the throttle from about 1/2 to 3/4 throttle.
I hope this helps. Remember to always have a clean filter and a new correctly gapped plug.