leading me to drink....

[zephead400ex]

I have a Pro Meg WB exhaust, airbox lid on, 42 pilot, 152 main, stock needle position, screw 3 1/2 turns out.

Before rejetting the quad ran fine, a little lean but not bad. Yesterday was the first time riding since rejetting. I rode for about 15 minutes and everything ran great. I was cruising along in 4th gear and the quad studdered (blub, blub) then died. It took a few trys to start but it did start but was very sluggish. It was acting like it was getting too much fuel and not enough air. I then removed the airbox lid, it ran decent at 1/4 throttle but 1/2 - WOT it studders like it did initially. At idle, it starts fine, 1/4 - 1/2 throttle it runs fine, at WOT (without being under load) it studders pretty bad and will die if the airbox lid is on. I have adjusted the fuel/air screw at all turns, still doesn't help.

At idle, if I start the quad with the lid on, it is sluggish. If I quickly remove the lid (without the quad dieing) it runs a little better as mentioned previously.

Any ideas? Should I go back to the 148 main? The temp today is around 65 degrees, yesterday the temp was around 55.

Any help/suggestions will be appreciated.

later

[Aceman]

I can't tell what's causing it but I believe 3 1/2 turns out on your fuel screw is to much. I think the limit is about 3 turns out but most guys have it around 2-2 1/2 turns out. Have you checked your float level? Is the overflow hose pouring out gas? Is your air filter clean?

[zephead400ex]

I have put the screw at 3 1/2 to try to get more air into the carb, obviously this has not worked so this can be adjusted with no problem. However, I have tried it at about every position that is possible which has made no difference. The filter is very clean. No gas is pouring out.

The only thing that I can think of that makes sense, is the main jet being to big. But with the full exhaust system, a 152 main *should* not be to large. Like I stated earlier, by removing the airbox lid it runs a little better. This leads me to believe it is needing more air. Does this sound correct?

thanks

[Aceman]

I don't have a 400ex but if it was me I would turn the screw in to about 2 1/4 turns out and go down on the MJ a couple sizes at a time until it runs right. I believe it's a fuel screw and not an air screw so you would be making it richer. I would also check the needle/seat and your float height.

[Werx615]

what does the plug look like?

[Werx615]

i dont think i would go to a smaller main, i have a 170 main and it runs great

[mikey726]

Sounds to me like your plug is fouled. Your 152 should be fine. You're getting too much gas from your pilot jet and flooding the plug. I had the same problem with the same jetting and the fix was to put the front two clips on the airbox under the lid. We've got two 400's running awesome at 42/155 with the clips under the lid(one stock, one with a Pro- Circuit slip on). You'll have to clean your filter more, but it should work.

[ledofthezep]

Thanks for the help guys, I'll let him know when he gets home tonight & we'll check tomorrow. The plug is new, but that doesn't mean crap...will check it 1st, then try the clip under the airbox lid gig...he's got a UNI filter w/outerwear so he'll be just fine if it helps...

Ride on!
LedoftheZep

[Samson]

Originally posted by Werx615
i dont think i would go to a smaller main, i have a 170 main and it runs great

Keihin and DJ sizes aren't the same.

[cals400ex]

Originally posted by Samson
Keihin and DJ sizes aren't the same.


also, a 170 seems really big unless yours is built pretty good. i run a 155 to 162 depending on the temp outside in my 11 compression 406 with stage 2 cam, x-6, filter, etc.


yes, a piped 400ex will run fine with a 170 jet in, but your hurting your performance.

[Bad Habit]

Hey Zepdudes, this may sound totally stupid, but take the bowl back off the carb and make sure the main did not fall out. What you're describing is exactly the way mine behaved when the main backed itself out from vibration. I guess I didn't get it tight enough.:rolleyes: It ran great for a little bit then wham, like someone turned off a switch, it would sputter at anything past 1/4 throttle. I took the carb off to go down a size on the main when I heard a rattle noise:huh

Just something to check.

[Samson]

Originally posted by Yellow416ex
Hey Zepdudes, this may sound totally stupid, but take the bowl back off the carb and make sure the main did not fall out. What you're describing is exactly the way mine behaved when the main backed itself out from vibration. I guess I didn't get it tight enough.:rolleyes: It ran great for a little bit then wham, like someone turned off a switch, it would sputter at anything past 1/4 throttle. I took the carb off to go down a size on the main when I heard a rattle noise:huh

Just something to check.

Yeah, read my "clogged carb?" thread. Same thing happened to me. :o

[Derrick D]

Check your plug. It is probably fouled or if you were running lean the ground strap could have melted off. Anyway that is where I would start.

[Bad Habit]

Originally posted by Samson
Yeah, read my "clogged carb?" thread. Same thing happened to me. :o


LMAO, I didn't read that thread until now.
When the thing is running perfect and then goes bad all of a sudden, it's gotta be something like that. Something has to change instantly (like a jet falling out or needle clip popping out) to make it act like this. No re-jetting needed, unless you count putting the jet back in as re-jetting. :D And I've never seen a 4 stroke instantly foul a plug like a 2 smoke can.

[cals400ex]

if it ran good for a while and then it ran like crap, more than likely something fell out of place. i agree and i have seen this before. first make sure the main didn't fall out. second, make sure the two skrews that hold the arm that raises the slide of the needle up and down didn't fall out. i would try a 155 or a 158 on the main if it is pretty cold outside.

[zephead400ex]

Originally posted by Yellow416ex
Hey Zepdudes, this may sound totally stupid, but take the bowl back off the carb and make sure the main did not fall out. What you're describing is exactly the way mine behaved when the main backed itself out from vibration. I guess I didn't get it tight enough.:rolleyes: It ran great for a little bit then wham, like someone turned off a switch, it would sputter at anything past 1/4 throttle. I took the carb off to go down a size on the main when I heard a rattle noise:huh

Just something to check.

Hmm...that's a b*tch! I haven't had anymore time to work on it this weekend. I will work on it tomorrow after work. I am definatly going to make sure the main didn't come loose. When I installed it I didn't want to strip it but I thought I had it tight enough...guess it can never be too tight:devil:

thanks guys!

[cals400ex]

Originally posted by zephead400ex
Hmm...that's a b*tch! I haven't had anymore time to work on it this weekend. I will work on it tomorrow after work. I am definatly going to make sure the main didn't come loose. When I installed it I didn't want to strip it but I thought I had it tight enough...guess it can never be too tight:devil:

thanks guys!


don't put the main jet in there too tight. snug should be plenty.

[SmokinEX]

Same thing happend to me, tried adjusting the screw but that did nothing either way, moved the clip one notch on the needle and it ran unreal.

[Chanman420q]

Originally posted by Yellow416ex
Hey Zepdudes, this may sound totally stupid, but take the bowl back off the carb and make sure the main did not fall out. What you're describing is exactly the way mine behaved when the main backed itself out from vibration. I guess I didn't get it tight enough.:rolleyes: It ran great for a little bit then wham, like someone turned off a switch, it would sputter at anything past 1/4 throttle. I took the carb off to go down a size on the main when I heard a rattle noise:huh

Just something to check.

same thing happend to me, i put the jet in, took a little cruise around my neighborhood, felt like a whole new quad, next day when i took it riding..... it was like..... a whole new quad again... total crap, went home, took the carb off and i could hear the main jet rolling around

[swamprider7]

I would be willing to bet that the main jet fell out. If its not that then maybe you could have fouled your plug.

[zephead400ex]

If this was a poker game, most of you dudes would have split the pot! The f'n main jet fell out. Then after trying to put it back in, the damn thing broke around the threads. I got the broken peice out, but have to get a new main tomorrow. I am glad to know that it will run fine once I get the new main installed!

And I am still drinking...:D :blah:

thanks dudes!

later

[Bad Habit]

Originally posted by zephead400ex
If this was a poker game, most of you dudes would have split the pot! The f'n main jet fell out. Then after trying to put it back in, the damn thing broke around the threads. I got the broken peice out, but have to get a new main tomorrow. I am glad to know that it will run fine once I get the new main installed!

And I am still drinking...:D :blah:

thanks dudes!

later


I win the pot, I showed my cards first.:macho :blah: :D

[Woodsrider]

wow, thats a small main. Im running a 160 and 2.5 turns on the screw. It popped real bad with the 155 mj.

[ledofthezep]

wow, thats a small main. Im running a 160 and 2.5 turns on the screw. It popped real bad with the 155 mj.

What's your elevation? We're aprox. 300' above sea level. It seems do run damn good with the 155...when it's in place!:D Once he gets another one we'll see how it runs when riding,...he hasn't gotten to ride it much with the new jetting---was stock B4.

[Woodsrider]

All of my riding (well 85%) is below 2500. and I jetted it at 850ft here at the house. Are you using Keihin (0r what ever) jets?