Am I stupid? (carb)

[MtnEX]

I have my team mate's race quad fixing it.

He had an issue with his starter relay that was causing him other issues not realized. See main power goes in the relay and then out into the harness. (will get into what to watch for there on the 400X later)

So he did a cam, UNI and HMF comp slip on over the winter and I jetted it up nice in the cold weather. He planned to get an EHS lid later so I told him that should compensate perfect for the richer condition coming in the summer. All was fine and then it seemed to fly apart on how i was running so he went jetting after having watched me.

He went up on the main jet and lowered the needle clip one slot to make it richer on the needle. Now that I got the relay stuff worked out, it is a bit rich. But here is where it gets funny....

What I have figured out is that it starts awesome, seems a little dirty on decel, but no popping, etc. But only starts and idles at high idle speed settings. It has that stupid D screw and D tool sucks. So I took it out and cut a flat head slot in it. I then realized it ran best with the pilot fully closed... lol.

So make sure I am not thinking stupid here... It is actually running on what is leaking by the needle and running RICH... and only does better at high idle cause it is getting more air. RIGHT?

I plan to take it apart and put the stock needle back or move the clip one or 2 notches leaner and see how she runs.

I think I had it 2 turns on a 42, stock needle and a 165 main in the winter with stock lid. (Pro X jets).

He moved it to an adjustable needle and went richer, and went to a 180 main (Pro X jets if it matters)

In his defense his carb was out of his head boot though and the air box boot was just sorta holding it against it so maybe that is what led him to go so rich?

[JOHNDOE83]

Your on the right path.

It seems as if your right, it may be running off the needle circuit at low RPMs.

If the carb came out the boot it would be lean not rich.

Its never to rich unless it sputters and doesnt rev out.

However, if you changed the needle the cut may be different and raising it up might not have been nessescary.

Its best to start over, seal everything up good then adjust the pilot to the standard 2.5 turns. After that put the needle back to a stockish position, If the 180 fully reved out on the top end leave it, im not sure what the prox jet scale is but 180 should be good enough to not worry as long as hes not bored out to a 426 or 440.

The slight leaness on decel might be from running off the needle circuit at low rpms, it might need leaned up so that the transition from pilot to needle is more "flowing" .

FYI, everyone thats gone over a 200 main jet has seen a massive increase in power at high RPMs, not saying youll have the same reaction but it may be worth it to buy the right jets from jetsrus and try the go big method on their site if this is a race bike, there is a stock bore 400ex here with a 210 main jet that will eat any stock bore on this site and some 450s.

[MtnEX]

Your on the right path.

It seems as if your right, it may be running off the needle circuit at low RPMs.

If the carb came out the boot it would be lean not rich.

Its never to rich unless it sputters and doesnt rev out.

However, if you changed the needle the cut may be different and raising it up might not have been nessescary.

Its best to start over, seal everything up good then adjust the pilot to the standard 2.5 turns. After that put the needle back to a stockish position, If the 180 fully reved out on the top end leave it, im not sure what the prox jet scale is but 180 should be good enough to not worry as long as hes not bored out to a 426 or 440.

The slight leaness on decel might be from running off the needle circuit at low rpms, it might need leaned up so that the transition from pilot to needle is more "flowing" .

FYI, everyone thats gone over a 200 main jet has seen a massive increase in power at high RPMs, not saying youll have the same reaction but it may be worth it to buy the right jets from jetsrus and try the go big method on their site if this is a race bike, there is a stock bore 400ex here with a 210 main jet that will eat any stock bore on this site and some 450s.

Right... see I jetted it up for him in the winter. Then around the time he did the lid swap he started also having electrical issues which were from the relay issues. So he started jetting on the carb and didn't get it back in right. So it was sucking air and lean and just acting up in general, which I think lead him to upping the main jet and also making the needle too rich.

I am just thinking the needle is bleeding over fuel at idle. So it does best at a real high idle setting and the pilot closed all the way. It actually don't run bad considering... I mean I am surprised. I could get it to start crazy well, and like I say it don't run nasty... it is just a little grumbly on decel is all... just ain't clean running in general. But I have rode worse.

I am going to set the needle to stock or put the non adjustable stocker back in, throw in the biggest main he has, set the pilot and go from there I guess.
Come on 5:15pm... lol...

[JOHNDOE83]

The stage 2 cam will make it rumbley when you decel, kinda like a loud piped harley right? but with the slipon instead of straight piped kinda sound?

That could just be the bigger cam rolling around creating that sound, it does make a completely diff decel sound with a bigger cam for sure, I noticed it right away when I did my stage 2.

[MtnEX]

The stage 2 cam will make it rumbley when you decel, kinda like a loud piped harley right? but with the slipon instead of straight piped kinda sound?

That could just be the bigger cam rolling around creating that sound, it does make a completely diff decel sound with a bigger cam for sure, I noticed it right away when I did my stage 2.

Nah... it is more of a 'spitty' trashy sorta sound like it's rich. And I think this has a stage 1 cam. I will have to ask again.

[MtnEX]

Hmf slipon uni ehs lid hotcam

2 turns out on fuel screw with a 42 pilot needle center and 180 main?

[Stickman400]

Sounds about right, maybe try lowering the clip 1 on the needle to the 4th notch and go to 2.5 turns, but it should run good with what you listed.

[MtnEX]

4th down is where it was and it would run with the pilot closed to no turns... at a high idle.

See it would start great, but if I slowed the idle it would die. If I opened the pilot it would die. If I left it at say 2 turns it would sit, slow way down, recover, repeat.

As I closed the pilot the thing would idle faster all the way to full closed.

So I took it apart, checked and saw the sync gap was too wide, delaying the lift of the slide. So I set it right, put the needle clip in the middle, etc. I still aint so sure the thing won't still idle with the pilot closed.

Right now it does not start quite as well, but seems a little sharper the very little I could ride it. And the idle, it was not bad but not as steady as I know it can idle.

I will take it out another half turn and just see what it does at 2.5 turns.

Could it be the needle? I swear the taper looks the same as the non-adjustable stck one.

[Stickman400]

I know the tapers on the needles are the same, so I don't think that would be the problem. I'm no carb. expert so I wouldn't know what to recommend. I always thought a high idle was an air leak but that's already been recommended.

[MtnEX]

Yeah I think so too. Think the taper is the same.

It is sitting on the middle clip now and the sync gap is corrected also.

I just put it all back together tight. Just fishing for a pilot setting.


Previously the high idle was from being set at high idle. If you backed it down much it would die. I tried adding pilot turns and it only got worse? That is when I started going the other way and could hear the idle getting higher until I realized it was full closed? Then I could slow the idle a little more. I assumed it was just idling on the needle bleeding over from being too rich. So I went in and set it back in the middle like stock and set the sync gap to .004.

I am not so sure it would not still idle closed. I could try it. Might be all of them will, I have just never been lead in that direction before by how one was idling?

Man do these things need a remote fuel screw!
But I won't complain. This one is a ton easier than mine. I cut a flathead slot in the D screw. I can but a flathead bit in there, put my left middle finger under it on top of the starter and turn it no problem with my left fingers. Mine I have to use a bit ratchet on cause it turns too stubborn. I think I will get me a 2012 fuel screw or a remote fuel screw when I get to working on mine again... lol.

[MtnEX]

No way this 42 pilot can be too much jet right? Dang it!

Needle clip back to the middle and tight sync gap made a huge improvement in the middle. Bounces right off the limiter clean with the 180 main. Installed the Sparky back in the HMF and that cleaned up the trashy sound on decel a lot.

After running a while though the idle slows a lot. I went back to closing the fuel screw and there was a nice spot the idle went up to 1600 but it dot stay it slows down.

I'm confused. I might try closing the pilot more.

Any ideas?

[MtnEX]

Ok I just set the screw at 1 turn and started moving out. It started slowing down and even started smelling rich by 2-2.5 turns and was slowing to 1200 rpm. I started going back closed fast and got all the way closed. Idles 1800 rpm closed?

What is going on here?

[MtnEX]

How abouts I top this all off by saying it ran awesome. Then after a few long decelerating to a stop it died and would not crank back?

It had fuel in the bowl when I opened the screw and also had spark!

Gonna put the original needle back in is all I know to do.

[MtnEX]

Ok well... maybe someone know the definite answer to this...

When you set the sync gap... should the idle screw be backed all the way off or set?

I am asking because I don't remember if I did that when I set it after moving the needle clip. But I did today when I put the stock needle back. I only got done in time to crank and set the pilot by ear. I had to turn the idle wide open for it to hit. Then it was a slow idle at 2.5 turns. I landed about one turn out by ear from there and it might idle a perfect slow idle.. 1300 or 1400.

I don't believe the needles are that different. Color is the biggest difference I could see aside from one being adjustable and the other not.

[MtnEX]

Gonna go ride it here in a little bit... Any thoughts?

Surely there has to be someone else here wiser than me on this?

And I would think someone who has experienced this before?

[MtnEX]

Well, I will keep updating this as I go I guess. If I get it all figured out the hard way at least it will be out there for the next person.

I went back to the stock non-adjustable needle and ended up about 1 turn out on the pilot. Idle screw wide open for about 1400 idle speed.

I tried and tried... this cured the random dying on decel. Must have been just as simple as getting it where the best spot was with the pilot open some. Really must have been running on the needle. But the bad part is it runs like poo in comparison.

It ran much better with the other needle. Now it idles slower and rougher, and has less power period, and you can choke it sometimes with a good throttle stab exiting a corner or something. It don't die, it just gasps bad and you have to let out, and by then down shift and try again.

The plug is black around the bottom where the ground strap attaches and the rest is barely a light sand brown. I need to go back to the other needle and somehow get it to take some pilot opening so it won't die I guess. But I have set the sync gap with the idle screw set to try first. I just doubt that is going to help.

Sitting here I am thinking I should check those ports that bypass the slide and butterfly, and possibly start to consider the jets although this should be correct (42/180). It did take a bit to hit the limiter in 3rd. Maybe I should double check the pilot screw too for tip damage, etc.