Help!400 will not idle

[Zeb400EX]

I took off my header to grind down the welds, and ever since I put it back together it won't idle. It run fine otherwise, but as soon as you let of the thottle it dies. Its really hard to start too. I took the carb off and cleaned the idle jet and the main,but still no idle. I got a 42 idle jet with the choke removed. I not sure where to look next. I thought maybe it could be the decompression valve sticking but I am not sure. Surely grinding down the welds wouldn't make my have to go up a jet size. I didn't really grind very much. Any ideas?:confused:

[coryatver]

did you replace the copper crush gasket for the header pipe? if not thats your problem right there

[drew416ex]

Originally posted by coryatver
did you replace the copper crush gasket for the header pipe? if not thats your problem right there

How would that make it not idle? I almost never replace mine and havnt ever had a problem.

[Zeb400EX]

Originally posted by coryatver
did you replace the copper crush gasket for the header pipe? if not thats your problem right there

no I didn't replace them, but I 've had the header off be fore and didn't have a problem. Seems like that also make it run bad all the way through the rpms. It run smooth when your on the throttle until it get down close to idle and then it backfires and dies. I have never replaced the gaskets so maybe they could be worn out.

[Zeb400EX]

gonna go buy some header gaskets today. Hope that fixes it. Thanks for the help.

[ginobili07]

Ya if that doesn't work you could try playing with ur idle screw if you haven't already.

[Zeb400EX]

well I changed the header gaskets and it started easier, but it still is backfiring and won't idle. Has anyone had to change the pilot jet after grinding the welds on the header? It just acts like its not getting enough fuel at idle. It does seem to have a little better throttle response.

[Zeb400EX]

Originally posted by ginobili07
Ya if that doesn't work you could try playing with ur idle screw if you haven't already.



R you talk about the pilot jet inside the bowl or the fuel screw outside the carb?

[katch26]

do you have the proper slack on the throttle cable?, mine was doing the same thing and the ilde screw didnt make a bit of difference turned out to be the throttle cable was to loose

[ginobili07]

ON my 2002 there is a screw that comes down from out of the carb and it takes a flat head screwdriver to rotate it, on the picture i attached it is the black tube going to a silver scre head right below the air/mixture screw.

[ginobili07]

here is a better pic disregard the red arrow, the yellow lines are pointing to your idle screw :)

[Zeb400EX]

thanks for the pics. I have adjusted that one but it didn't really seem to make a difference. I 'll check on the throttle cable

[Buelligan]

Check the carb isolator located between the carb and the head. It is an aluminum and rubber part. The rubber is bonded to the aluminum and sometimes comes un-bonded causing a lean condition which will cause the motor to pop while idling and then stall.



:devil:

[CarGuy7a]

Originally posted by Zeb400EX
well I changed the header gaskets and it started easier, but it still is backfiring and won't idle. Has anyone had to change the pilot jet after grinding the welds on the header? It just acts like its not getting enough fuel at idle. It does seem to have a little better throttle response.

you said it right there. not enough fuel at idle. either your mixture screw is out of adjustment or your pilot jet is clogged seeing that you said it was popping and carrying on. check both.

if that don't work try bumping the pilot up to a #40

[bigredisb]

This should not have anything to do with removing a header but I have had this same issue on a 500 Rubicon that my dad had. What we found was a leak in the intake manifold between the Carb and the head. How I found it was by using a little propane torch that is NOT LIT. Open the gas valve and wave it around that area. On our 500 it started idling as soon as I found the hole because the propane is acting as the fuel that your not getting from the pilot jet because you dont have enough vacuum in the carb to pull fuel through the pilot.
I hope this makes sense. Its what I use on older GM trucks with a ton of vacuum lines that always crack and suck air.
Like I said it might be a long shot but its easy to try.

[katch26]

you could also spray around with the aerosol starting fluid......same thing

[Zeb400EX]

I took the pilot jet out again tonight and it looks like there might be some very little inside of it. I did have any small enough to run through it but I got it soaking ing some carb cleaner over night and I am going to try and a piece of wire small enough tomorrow. I also put a #48 jet in it and it would idle but I had to turn the idle screw in all the way in or it would die. So I know the 48 is to big. Hopefully something will come out of the jet. If not I might just buy a new #42 jet and go from there. I guess I could try the stock jet too. Thanks for the good advice guys.

[Zeb400EX]

fix it! Pilot jet had something in it. I cleaned it out better this time than before I guess. I think letting it soak in the carb cleaner help though. I am glad its fix now, cause this thing was driving me nuts. Guess I know to clean it out better the next time. Thanks again guys for all the help. I still have take back apart, cause I left out the little plastic baffle thing around the main jet.:rolleyes: