250-500cc Wr250 300 kit 2009

Maybe its to far down

The pilot only is involved from idle to about 1/8 throttle however the air screw works all the way through the needle circuit. If the pilot is too small you have to turn the air screw in and lower the slide to keep it from idling lean. If the pilot is too big often times the slide must be raised so high that it is partly idling on the needle and the air screw is backed out beyond 2 1/2 turns. From my experience when the pilot is the correct size on a Mikuni the air screw will end up being between 1 and 1 1/2 turns out.

At full trottle i think the fuel wil also flow true the pilot jet or am i wrong. Maybe less as at iddle but large or small pilot jet will effect the air fuel ratio at full trottle a little i think.
Also i was thibking about the short pro circuit muffler maybe this has effect also on the air fuel ratio.
I will do two test with the larger pilot jet and after the long muffler of this effects the fuel air ratio.

Technically the pilot is still involved but once the slide is raised past about 1/8 there is very little siphon affect and almost all the fuel is drawn through the main and around the needle until the needle is high enough that the main is flowing all it can flow. I've had different pipes and silencers on my wr and the changes required very little adjustment (usually one size on the main and maybe 1/4 turn of the air screw). The main sizes you are using would have fouled out my spark plug in a few minutes, that's why I think you might have a float needle valve restricting the flow into the bowl so no matter what size main you put in it it has little to no effect. That or you have an air leak that is letting air bypass the carb.

Oke thanks for your explaining.
I also have new float needle etc installed for a few monts ago. Also did the testvyesterday with the fuel hahn open but the fuel comes realy fast out of it the floating musst be ok. Ive seen some people in usa riding main 470 480 with the 300cc engine maybe i need a little more here in holland.
Its nowrre lower sealevel then were i live.
Also have the checked on airleaks aswell.

You have to give the engine what it wants and not go off of what others have for jetting, I am worried because the pic of the snow white plug in your earlier post looks very lean.

Yes i wil try for testing 520 main

Now the bike is getting full with fuel when trial riding
And i have to burn it for 3 gears full load.
I am sick of the mikuni
I will buy a lectron or pwk 38mm
What would be better the keihnin or lectron for the 300
For motocross and enduro use

Buyed a lectron today hope this thing wil work
Any sugestions for needle mods etc.

Best regards