I probably should not comment on this since I don't know diddly about jetting wrt exhaust on a DVX, but from my knowledge of dirt bikes, typically the pilot jet remains the same no matter what exhaust you have since at low throttle, exhaust does not have a big effect, but the main jet which has more of a high throttle impact, is usually leaned down when a higher end exhaust is put on. And I wish I can tell you why, but I don't know why. I just know most manufacturers of carbs will recommend lowering the main jet when high end exhausts are installed.

 

Actually when I went with an aftermarket exhaust I went up on my main jet size. Stock is a 130, I went up to a 155. and I went with a 25 pilot jet where the stock is a 22.5. Im not very good with the altitude conversions though. With a pipe, you take your airbox lid off to dump more air into your machine, with more air your going to want to dump more fuel, thus giving you more power with the right air to fuel mixture, and all of which is escapin through your newer high flow pipe. I will say though I am not a fan of the K&N filter or the HMF pipe lol. The pipe is super loud, but its up to you and how you ride. Also your going to want a new needle and E-clip, and I was running the 3rd notch down from the top with the eclip on the needle and I turned my fuel screw 3 turns on the carb.

 

Cory, your quad is going to be psychotic. Air box open, more air, so up the main and pilot for more fuel, plus richen it up with moving the notch on the needle and lean it out with the screw out 3 turns. Damn thing is going to go postal!

I sometimes get dirt bikes where the previous owner tried all sorts of tricks to improve HP by going from a 30 pilot to a 50, trying all sorts of main jet sizes, screw in or out the air mixture screw way too far, adjust the needle collar... etc. etc. They eventually get so fed up with trying to get their bike back running right, they sell it for way less than it is worth. I take it, and set everything back to stock, clean the air filter (which seems to be something dirt bikers don't like to do and causes them the most grief trying to get their pilots and air mixtures correct) and make slight adjustments to get it back into a fine tuned machine.

Not saying what you are looking to do doesn't work for you and it probably gives you more speed at the right time. I have to believe the engine may not be able to burn all the extra fuel coming in and thus some of the fuel is just going out the pipe unused. I certainly don't know for sure, but for a normal weekend rider, they are better off going with stock settings or settings recommended by the pipe and/or carb manufacturer. With the fuel and exhaust system, every action has an opposite and equal reaction meaning, if you change one thing, you need to change another and in the end, you have to assess if you are better or worse than you were before for the type or riding that is being done.

 

I talked to a motor builder who is a good buddy of mine because when I bought my alba pipe the "experts" at Alba said to run my carb like this. So I did and my machine ran like a bat out of hell, there was fuel in the pipe causing it to backfire a little and shoot flames on deceleration. But after I installed my big bore kit I upped my main to a 180, and started tweaking but like you said, I couldnt find the results I wanted. and I started having problems with my clip in my diaphram in the carb literally blowing it self apart and the needle becoming loose causing my machine to idle fine but would bog as soon as I hit the throttle and was running like the choke was on. so I set it back to what my buddy told me, and what the folks over at Alba suggested for a race machine. and it was fine but just couldnt get the results I wanted from my BBK. So I took the carb off and odrered the Edelbrock carb. I would never keep a stock carb on a machine as long as I live after seeing what this carb did for me. Here are a couple pics of the new carb, lol you can see by the fuel line how much fuel I am dumping into my motor now lol, I go through so much gas now, I would be lucky to get 20 miles out of a tank. When I was stock I got about 65-75 miles per tank. You should try that combo out on your DVX with the jetting I was talking about in the post above, makes a huge difference with a pipe!
[attachment=147081:006.JPG][attachment=147080:SSPX1346.jpg]

 

That makes a lot of sense Cory. Many people with dirt bikes do the same, trying to find the perfect combo and then get so confused as to why something is not right. Then instead of getting back to base and work from there, they get frustrated and sell the bike. Which is fine with me because I can sometimes get it for cheap, simply get the carb back to stock, and have a nice running machine.

We just picked up a Yamaha YZ125 for my son (dirtz) last week for dirt cheap. It runs OK but you could tell the engine was getting too much fuel based on the heavy sound the engine made and the amount of smoke. Found it was jetted with a 50 pilot and 320 main. Switched to stock 35 pilot and what a difference. Since it has a Pro Circuit pipe, going to use the Pro Circuit recommended main of 340 instead of stock 350 (yes these mains are that big!). Also leaked fuel like crazy out of the bowl. The previous owner didnt think about adjusting the float.

With the combo you mentioned, I figured your engine had to be sucking for gas and spitting some out the pipe. But for racing, I am sure gas usage is not an issue. Or do you have to get a modified tank to hold more gas?

 

NO I use my stock tank, we only run 4-5 laps on a Motocross track and the track average is 3/4 to 1 1/2 miles long. I fill my tank about a 1/4 full before every race and I always have enough to get me back to the pits but not much more lol.

 

with the Edelbrock carb do you need to adjust anything when you buy it or do you just install and go ? Im leaning towards the Edelbrock carb now it makes more sense.

 

the edelbrock will have to be adjusted some but nothing major. just getting the lean and rich mixture correct (pretty simple with the tool given). for the most part it is install and go.

 

One thing I noticed on this DVX 400 is that I can't take it out of choke all the way when riding. It will bog down if I do. I let it warm up for a few minutes and put the choke down about halfway and it is OK, but can't release all the way without it bogging down. Seems like a mixture problem and not getting enough fuel. Haven't taken carb off yet to clean and not familiar with these carbs yet enough to know what to adjust.

Also, when cold, and choke out, if I give it gas it bogs a bit and I have to back off. Also appears to be a symptom of not enough fuel or too much air.

Before I start studying these carbs, anyone have tips for adjustments on the stock carb?

 

when i had the stock carb...i installed a push pull style. i didnt like the one on the handle bar.

 

<div class='quotetop'>QUOTE (lakia_dvx400 @ Feb 5 2010, 06:34 PM) <{POST_SNAPBACK}></div>

when i had the stock carb...i installed a push pull style. i didnt like the one on the handle bar.[/b]

Yep I did the same thing, a little black knob on the carb itself, pull out to choke, push in for no choke, super easy, way better than the choke on there, and its a cheap part too

 

Also make sure the cable isnt getting suck or hung up on anything, sometimes if it is tight somewhere when you turn the bars it will engage and disengage the choke

 

what about air mixture on the carb itself. Not sure where that is on this carb. Its certainly not obvious

 

there is a copper screw on the bottom side...unfortunately not very easy to get to but you can.

 

I have a 06 artic cat dvx 400 all stock i am purchasing a big gun eco exhaust in a day or to wat jetting should i run an is there anything else i should get to make it run right ?

 

i have a i think 03 dvx 400 with a hmf slip on and a high compression piston in minnesota i don’t know elevation but i need to re jet the carb it was perfect before the high compression piston what size do i need

 

It will be trial and error. Get a couple sizes larger and a couple smaller.