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]

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

[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..

[skemp]

I assumed you would be using at least premium... I am surprised you haven't detonated that thing to death yet. That is likely your problem right there.

[JP400ex]

Think I should still try a smaller size main, or just change out the gas and see how it runs first? Im picking up a 165 tonight.

[JP400ex]

Ok, I lowered the clip on the needle to the 4th position down, drained the tank completely and put 94 octane in and changed to a 168 main jet and it seems to run MUCH smoother now. I may try to go down another jet size tomorrow. Thinking like a 162 if they have one. It still pops a little at 1/4 - 1/2 throttle when you let off the throttle but all in all it is running way better. Im wondering if maybe i should put the clip all the way down to the 5th spot.

[skemp]

Go with a 162 or 165. Also, put the needle in the middle clip. You could maybe put it in the 4th from the top, but I think it would probably be too rich. Also, make sure your fuel screw is out 2 turns. That may have something to do with the popping if it is in too far. A 42 pilot should be good.

[JP400ex]

My screw is out 2 full turns. It definetly runs better with the clip in the 4th position than it did stock, if anything its running a little lean at 1/4 throttle.

[cals400ex]

Originally posted by JP400ex
My screw is out 2 full turns. It definetly runs better with the clip in the 4th position than it did stock, if anything its running a little lean at 1/4 throttle.


see, i prefer my clip in the 4th position too. many disagree, but mine was smoother. in the summer months, it was borderline. you almost need a position right between 3 and 4 in my opinion. however, one of those washers that you can put under the needle might just solve that problem. i definately wouldn't run it in the 5th position. i get a little popping on deceleration too. however, the bike seems to run good and i am getting good plug readings. yes, i would go smaller than a 168. good luck

[JP400ex]

Well, I think im finally dialed in!!! I dropped it down to a 162 and it is running awesome. It was my first time i had the quad on dry ground too so it was gripping pretty good. :)

Im not going to go any lower than this. I think the 162 sounds perfect in there.

[cals400ex]

Originally posted by JP400ex
Well, I think im finally dialed in!!! I dropped it down to a 162 and it is running awesome. It was my first time i had the quad on dry ground too so it was gripping pretty good. :)

Im not going to go any lower than this. I think the 162 sounds perfect in there.


glad you got it dialed in. i assume the bike runs better now than with the larger mains in?