bike running rich

[ford832]

Turning your black plastic idle screw has no bearing on rich or lean-it simply raises the slide a little-exactly the same as when you twist the throttle a little bit.Once warmed up,turn your idle screw to the left until the bike quits,then turn it to the right a bit,start it up and set the airscrew.Once done,set the idle where you like-I like mine to stall after a few seconds but some like them to idle.Regardless,keep the lowest idle setting you can.

[kawi250]

OK so this time I checked the position of the air screw and it was one turn out. So I turned it to the left a quarter turn and rode it from there it seemed a little better but rode pretty much the same.  It isn't bogging or anything and it seemed to have good bottom end power. I then readjusted my idle to a lower idle because the last time I set it high I felt it made the bike bog if it sat too long. Before I ride next should I put a new plug in and check it at the end of the day to track my progress? And thanks again for all the help now I can get my bike running correctly any time I want haha

[Coop]

Your air screw should be about 1-1/2 turns out; anything less than 1-1/2 or more than 2 and I always re-jet.

[Chokey]

Print this out and study it. It will help you to understand jetting.

I highlighted the section that deals with the pilot circuit for you.



 

[ford832]

OK so this time I checked the position of the air screw and it was one turn out. So I turned it to the left a quarter turn and rode it from there it seemed a little better but rode pretty much the same.  It isn't bogging or anything and it seemed to have good bottom end power. I then readjusted my idle to a lower idle because the last time I set it high I felt it made the bike bog if it sat too long. Before I ride next should I put a new plug in and check it at the end of the day to track my progress? And thanks again for all the help now I can get my bike running correctly any time I want haha

Try turning it 1 1/2 out to see what you get,then try at 2(I like to go in 1/2 turn increments then fine tune from there).Ideally,go back to the first post and do it that way but if not,try it at various settings. 1/4 turn different than what you had won't usually make a huge noticeable difference in a "seat of the pants sort of way"
As for your plug,I'd leave the same one in.Plug chops are great but checking it after a ride won't won't tell you that much unless you're super rich or super lean everywhere.

[dhamblin]

All my bikes are jetted pretty well and they all will also idle indefinately, i'm open to learning new things though so could someone please explain why a 2t MX bike shouldn't idle.

I know the factory Yamaha's were set not to idle; I would guess most of the factory and top pro ones did not.

Is was done for a couple reasons, to help off idle throttle response and help with jetting.  My '06 YZ250 will idle for about 15 seconds (I am not in serach of that last bit of response as I can't tell the difference  )  This wasn't done by leaning it to where it wouldn't idle, the pilot was set correctly but my understanding was the throttle stop screw was set for no idle.

I used to have a good article by Dick Lechien (Ron Lechien's father) on setting up the idle, I'll se if I can find it or a link to it).

[Recovered]

What I like to see for a main jet chop. Nice ring with just a hint of color on the tip.

[RedFoxCR]

Howdy, fellows! I looked through the article and the main question worrying me is:
DOES the air screw really affect mid and top-end throttle response??? I've got Keihin and they say the air screw can only affect from zero-opening to 1\8 opened throttle. What do you think?

[Recovered]

All circuits are active at WFO. The lower circuits are contributing but at a small level. The influence is small enough that unless a problem occurs at WFO after changing the pilot or needle it can be ignored. The only time I've seen it cause problems is on highly tuned big engines. The chart you see about a circuit's effectiveness is about it's usable influence. Generally if you are happy with the way it runs you're probably OK.

[ford832]

Well Kawi250,what was your final result?

[kawi250]

To be honest I am still trying out new settings and the weather has changed and become hotter and more humid so I'm still trying to catch up with it. I did ride southwick last Sunday though and the bike was running awesome tons of power even in the lower rpms.  It also got right up to the top of every gear with the slightest crack of the throttle. I still plan on adjusting it again in the near future but at least now I know how to correctly do that haha. Thanks to all for the help

[ford832]

Good stuff.You always have to adjust when your temp/pressure/elevation changes but you're certainly ahead of most .A guy I used to ride with always raved about how good his KX ran spring/fall as compared to the summer though he didn't know why.You couldn't convince him to tune it though.When he sold the bike,his carb/suspension had the exact settings as when it rolled off the showroom floor.You'd be surprised how common this is.

[RedFoxCR]

I understand that fella!!! Nothing can be worse than unmounting the carb with bare hands at minus 20 C... All pipes, hoses, intake behave like concrete. Yak. Hate that.

[kawi250]

Its worth while to understand especially when its really fairly simple to do when before I thought it was a complicated and hassle to dial in

[RedFoxCR]

That IS comlplicated, i mean, not unmounting the carb but installing it BACK. The rubber hoses are very stiff.