Here's the deal guys...

Had my quad 'hooked up'..
I have a K&N in my stock airbox with lid.
I have a full Yoshimura exhaust.
I 'had' unknown jetting because I didn't do the work.
Maybe 1200 ft elevation at my house...

I didn't get much gain from all this. Later I noticed it was running rich. I started getting black soot in the exhaust tip. I did plug reads and it seemed to be running RICH on all circuits. But it was starting really well.

I pulled the carb and found it had a 155 main and a stock 38 pilot... needle in the 3rd clip slot down. I took it all apart, cleaned it, etc.

The pilot screw was many turns out when I turned it in to lightly seat.
I backed out to 2.5 turns.

The needle holder the main goes in... it was not screwed all the way in before the locknut was tightened. So I did put it all the way in, put the same main back and just raised the clip on the needle to the second slot down.

It seems a little on the lean side now, but not too much. The color on the electrode, etc is just on the 'light' end, yet I'm getting some black on the outer metal.

Now it cranks like crap though. It's got the cold start blues. It will start, but then quickly die several times. Plus the idle RPM really increases once the engine is hot.

I know something is off... but I can't seem to get it tuned out to save me.

Does it have to be RICH on the pilot circuit to start well?

I 'think' I have had the screw as far out as 3.5 and could smell it was rich from the exhaust and it still didn't crank much better. So I went back to 2.5 turns and went in to 2 turns to try that. Still no good. I guess I can try 2.25 turns?

I'm just lost and very frustrated with this.

I've even thought of backing the dang thing out like 4 turns to see if it starts like it used to... and if so, maybe even going to a larger pilot... rich or not.

 

Quick temporary fix, while you work the jetting out......

If it is a cold blooded starter, pump the throtle a few times before you start. It is a pumper carb, and this will inject raw gas, and richen it up immensely.

Maybe also turn the idle up a little, and that will keep it running while it warms up.

 

Yeah, I'm already doing both.

 

This is tough to do over the net but from the sound of it you "might" have a vacuum leak. I would spray around your boot and gaskets with carb cleaner to look for the leak.
Let us know what you find.

 

<div class="FTQUOTE"><begin quote>Originally posted by: Doctorturbo

This is tough to do over the net but from the sound of it you "might" have a vacuum leak. I would spray around your boot and gaskets with carb cleaner to look for the leak.

Let us know what you find.</end quote></div>

Possibility I guess.


Are either of you REALLY FAMILIAR with the 400EX carb setup?... Enough to know what I am talking about when I say... the top line/hose that runs from the carb over to the tank shield...

What about that thing?... Could that be it?...
I'm not sure how that's supposed to go over at the tank shield.

 

<div class="FTQUOTE"><begin quote>Are either of you REALLY FAMILIAR with the 400EX carb setup?... </end quote></div>
I'm not, so I don't know about the routing of the hoses.
I would still check for a vacuum leak just as good procedure.

 

I haven't found any leaks yet.


It seems like I have to run the pilot screw out until the circuit is overly rich in order to get it to start in cool weather without firing and immediately dying seconds later several times over.

Are you all rich on the pilot circuit or running 40-42 pilot jets to get good starts?