yamaha xj650 running rich?

[stobrien]

I am at a loss on my bike. It has a hesitation right at the start and after its going it runs perfect. The idle is steady and strong. The power after about 2500 rpm is great but I just can't get is to launch very well.
I have checked my plugs and when idling it is running rich, but when I have taken it for a good ride and take out the plugs they look good.
I have had my carbs cleaned and run seafoam through them.
Where should my air/fuel mixture adjustment be set? They are now about 4 turns out which seems a little excess.
The Haynes manual does not have much on setting the carb.
Can any one Help

[BuzZz]

With the mixture screws out 4 turns, I would bet your piloit jets are too big. Try the next size down and see how it runs at low rpm. You don't want the mixture screws turned out 4 turns on any bike, nor all the way in. 1-3 turns out, closer to 2 is better, is a good general rule for setting them on most carbed bikes. If you have the right jets in the carbs, a quarter to half a turn on the screws makes a noticable difference, if you can crank them around all over and not change the way it runs much, the jets are wrong.

Give it a try and see. Good luck

[kar_the_terrible]

I have a dumb question, but its gotta be done sometime:

How do I know if the idle mixture screw reglulates air or fuel? Convention dictates that screws regulating air are at the back of the carbs, while fuel ones are near the intake manifolds.

Now I've heard that on an xs400 (mikuni carbs) the idle mixture screws are in the front but regulate air. Is this right?? In any case do I turn in to richen the mixture or out???

-K

[BuzZz]

Could be either, depending on the carbs. To the best (such as it is) of my recollection, Mikuni's use the screw to add fuel to the air flow, Kehein's use it to add air to the fuel..... but I might have that backasswards.