Check out this vid of my EX running

[JP400ex]

Anyone whos got a good ear for engines want to take a listen to this and tell me why my engine sounds like crap? I just can't get the jetting right or something. All of my motor mods are below.

You need the latest Divx codec from http://www.divx.com to watch it.

http://parsons.dynu.com/400ex/416run.avi

[Out_Sider]

well damn son....you dont need a 185 main jet!!! i'd say a 155 at the most! but i'll listen to the thing and see if theres any other problems

[JP400ex]

Thats what everybody tells me but if I go down to a 175 it pops real bad when i let off the throttle. I've seen plenty of guys on here that have like 170-175 but they are all a little higher elevation than south carolina too! :-)

[skemp]

The main won't have much of an effect upon letting off the throttle. Something isn't right with it though, because that is a turd if I ever heard one. You are undoubtedly rich, and I also wonder where your fuel screw is. This is what I would do. If you do it this way, I am confident that you will fix your problem.

1. Clean your air filter if it isn't already
2. THOROUGHLY dissassemble and clean your carb. Clean out all the passages and jets. Also check the needle seat.
3. Set the fuel screw to 2 turns out with that 42 pilot. Put the clip in the middle of the needle. Put in a 162 or 165 main jet.
4. Put it all back together, and check for leaks and make sure that everything is sealed up well.

If it still doesn't work, or run significantly better, there is something else wrong. When did this problem start by the way? What did you change? Anything over a 170 in a mildly built motor is overkill. All these guys put on pipes and keep throwing more fuel at the poor things until they won't run, and then wonder what is wrong. Bigger jets don't mean more power.

Go try what I said, and if the problem hasn't gotten better, we can start trying other things. Good luck.

[JP400ex]

It basically ran this way when i got it. It had a 200 main in it and i would notice some serious hesitation when i would stab the throttle. I started lowering the jet size and when i put a 175 in it would pop a bunch. I've never gone any lower than the 175. I think I may put a 162 in tonight and see what it does.

One question, the head is race ported on it, if it was done "wrong" or maybe too much, could this require the larger jet?

What octane gas you using??????????

[JP400ex]

87

[mustang]

why are you using 87 octane w/ an 11:1 piston

[JP400ex]

Cuz im a dumbass i guess. :-)

I just talked to someone else and they told me to drain it and fill her up with 94. He said i don't have to run race fuel but 94 will make it run alot nicer. Im going to try that and mess with the jetting after i get the better gas in. I think i will start off with a 162 jet for winter.

Houston we have a problem. Definitly go up to the 94 and see how it does. Try finding some high octane over 100 and mix it with the 94 and see how it does..

That gas is definitly part of the problem.. Your jetting might be fine. Try the gas first before tearin into your carb..