Help me out carb experts!

[400exMO]

I'm having troubles with my quad running. I have a hmf slip, k@n filter and I'm running the air box lid. I have a a 160 main jet and 42 pilot, and everything is stock. When I'm at complete idle and pop the gas it bogs before it revs. Any help??

[ride red 14]

mine does the same thing did you take the carb apart and clean it ? if not try that and see if it helps then check your spark plug and make sure it isnt running lean or rich

[400exMO]

carbs clean as a whistle. I'm under the impression it's lean, but plus looks fine:confused:

[ride red 14]

maybe the jets gloged does it leak gas if it does the float might be stuck open and if your plug has white on it it is running lean

[400exMO]

well I've just recentely cleaned the carb to a shine, no gas leaks, clogs, or stuck floats. I just need a carb expert to access the problem w/ my jetting.

[400eXr1d3rZ]

Check your air/fuel screw, try it at about 2.5 out. Also check you plug and see what it looks like.

[400exMO]

There's where i need more quidance. How do I access my air/fuel screw and which way do i turn it out?

[GPracer2500]

Your Accelerator Pump failing to perform at it's best. Unfortuanately there's no easy way to tune the EX's AP. Your best options are to make sure your pilot circuit is properly tuned and to raise your idle speed. Raising the idle speed often lessens the bog to the point where it won't happen unless you are purposely trying to make it happen.

This off-idle bog condition is a fundamental deficiency in the way carburetors work. The AP is suppose to cure it but often fails to meet that expectation. Here's why this off-idle bog happens: When the throttle get's whacked open from low rpm, the vacuum in the venturi changes quickly. The pressure signal that pulls fuel through the jets gets momentarily out of whack. The result is a temporary lean condition that persists until the carb's pressure signals normalize and flow fuel normally. The AP squirts raw fuel into the engine to compensate for the temporary lean condition. It does this through a mechanical linkage so its function is independent of vacuum.

HERE (http://www.exriders.com/vbb/showthread.php?s=&threadid=229923) is how to tune your pilot circuit.

Good luck!

[Mobile Dyno]

You are running to big of a pilot. 38 is stock. Is you jetting with a synojet kit? If not then a 160 is to big for running the airbox lid on. Try a 150 or 148. Check this link out for more help. Your to rich.

K160 is with the lid off.
Jetting with HMF slipon (http://www.exriders.com/vbb/showthread.php?s=&threadid=246519)

[jrm03]

400exMO if you decide to change the pilot back to the stock or a lil smaller than a 42 let me know if that works for you. I am having the exact same problem that you are. I am also running the 42 and I messed with the mixture screw and it still does it a lil. Is it possible to completely rid this problem or is this something some of us will just have to live with

[Wheelie]

I agree with Mobile Dyno--you're running way too rich.

Step down to the stock 38 pilot and step down to a 150 or 152 main.

Remove the airbox lid and see if it runs better.

[400exMO]

Unfortunantely I need the airbox lid. My jetting is what Colby from C@D suggested, but to bad jetting's not as easy as someone telling you what to run. I'll try stepping down my pilot and main. Any other suggestions???

[jrm03]

Correct me if I am wrong but to solve his problem with the stumble from idle the main jet would have nothing to do with it right. Just the pilot jet and mixture. I am just learning these things and I have the same situation

[400exMO]

I just talked to COlby and he told me to adjust my air fuel screw. SO I'll go try that and report back.

[400exstud]

You are, indeed, too rich on the main jet. When you stomp on it in a low RPM, the main jet simply floods the engine, causing your bog. Do not be afraid that you are going to go too lean with your main (as many people fear of doing). I am sure that you could run your mods on stock jetting and cause not harm, but you would lose power.

Just to tell you where I stand, I have the HMF full exhaust, quiet core installed, K&N filter, and lid on. Pretty close mods.

I am currently running a 155K for my main. This is actually my winter jetting, but it works good in the summer without the quiet core. I should really bring it down to a 152K though.

You should be somewhere around here. Hope all of this helped.

[GPracer2500]

The main jet has little to nothing to do with bogging that occurs when whacking the throttle open from idle or very low RPM.

[400exMO]

Well I adjusted the fuel screw and the problem was extremely minimized. I'm thinking about putting some vents in my airbox lid. Would the jets be fine if I did that?

[jrm03]

I put 3 1inch holes in my lid but I have not gotten to test the main yet so I will post that if I beat you to it. My guess you may have to jump one size at the most depending on your settings now.

[GPracer2500]

400exMO, if you vent your lid then that will probably require another jetting change. Sorta depends on how "spot-on" your jetting is right now and how much venting you do. For example, if your a little rich right now then venting the lid might bring you right to where you want to be. If your a little lean right now, then venting the lid will make your leanness worse.

[cals400ex]

i would try a keihin 155 mainjet and go around 2.25-2.5 turns out on the fuel screw from being lightly seated. see if that helps. if not, your idle may be a hair too low. make sure you don't have air leaks around your carb either.