weird zrx carb question

[yamahansolo]

I unplugged the vac advance the other day so it wouldn't befully advanced at idle... now I get a vibration and plug. Show lean.... before warmed up it smooth even with choke lever. Pulled out... once. Warmed its a little rough.
Tried the gas cap and runningin prime to. Richen nada. Still vibrates. I shimmed the needle .5mm and there was a tinsy improvement...
Myquestion is according. Toall the research I have done on carbs if the idle mix screw is on the motor side of the carb tighteneing the screw richens it and loosening makes it leaner... this one feels like its the opposite... I seem toremember someone posted these richen by unscrewing...??? Any "official" idea which way is correct?
So. Far my theory is my mains are too small ... and pilots.its harder to start in the cold than my stock carbs were. ... I think it was running a little lean at idle with it advanced. And at 1/4 throttle andup the vac advance retarded the motor enough to compensate for thean pilots and main jet...??? Any ideas??? Thanks

[yamahansolo]

Oh and the more I tighten the idle mix. Screws the rougher it gets...????

[skids]

To answer your question (I think), screwing in the mixture screws makes idle leaner. Second, I can't tell by your description if you plugged the vacuum port of the No. 2 carb when you disconnected the hose, but if you didn't, it will suck air into the carb causing No. 2 to be lean.

[skids]

Disregard my last posting. I noticed your subject line was for a zrx. I know nothing about those carbs.

[yamahansolo]

Its ok... I did plug the port and I even sprayed carb. Cleaner all around vacuum hoses looking for leaks and nada. All the websites with carb tuning info state that ifthe screw is on motorside it richens when closng it and leanes when openng... the zrx is kind of. Like. The xs but the screw is on the bottom

[petejw]

yep screwing the idle mixture screws in makes it lean at idle
and screwing them out makes them richer, they control
fuel flow.

are u running fuel filters, u mite have some muck in the carbs?

what jets are u running?

try the mod that tadracer came up with regarding the vac adv, works really well.

[cywelchjr]

The websites are wrong, and backwards. If the screw is on the engine side, it controls fuel and screwing it in leans the mix, out richens. If it's on the air cleaner side, out leans and in richens cause there it's an air control. The ZRX carbs use a fuel mixture screw as pete said. So to richen the mixture turn the screws out some. And if you modded the carb like pete did with the barb is the right spot by the butterfly as he found there shouldn't be any vacuum advance at idle as there should be negligible vacuum until the throttle opens some, but it's all about getting that very small hole in just the right spot plus having the restriction in it.

[yamahansolo]

Sorry. Forgotto mention new fuel filter... new plugs...
Will be doing the vac advance mod maybe this. Weekend...
I am just trying to basically wrap my head around the plugs looking lean but the bike vibrates after warming up??? The plugs have zero. Fouling no black stuff. Not having the vaccuum advance plugged in should do. Nothing. With these carbs it just smoothes the transirtions for the old. Ones I believe...
Isn't there. Somekind of math to get you in the right ball. Park jetting wise. I. Mean the engineers don't just pull. A number out of their ass... there's got to be some way to calculate pretty close what you need.

[yamahansolo]

Fixed it.... 1 turn out from seated. . Rode through the mountains today and got almost 41 mpg... so it was rich even though the plugs were not black....