ES250 air screw - which way to turn it? !!

[stogadog]

This may seem like a really stupid question but which way do I turn the air screw on my carb to weaken the mixture? my bike is running a bit rich at the moment but Ive never actually found out which way the screw works!
Yours in stupidity - Andy...

[NinthOption]

If the ES250 is the same as the TS250, then tightening the screw makes the mixture more lean.

[manumensa]

Hello,

I think carburator BVF, Bing, Mikuni, ... have a air screw and
Dell´Orto, ... have a fuel screw.

In "miraculis" the original carburator in ES 250 model: BVF N 271-0
Never saw this model. I suposse same air screw BVF family.

Thigten air screw and unscrew 2 1/2 . You run and feel.
if runing rich: unscrew to weak.(1/8-1/4 turns)
if runing weak: Thigten to rich. (1/8 -1/4 turns)
On the contrary carburator with fuel screw.

Saludos,
Manuel.

[stogadog]

Thanks fellas - plus the PM from Dave. Sorry it's took a while to answer - not been online much. We do seem to have contradicting info here though!

[stogadog]

Well here's a bit of an update - I took it out a couple of nights ago and noticed that on full throttle it was running incredibly rich and smoking loads. Got to the point where I fouled a plug and it stopped altogether. With a new plug and some gentle riding home all was well. Aha - I thought it's just running rich on full throttle - maybe the main jet is worn. I checked it out tonight and the main jet had unscrewed itself and was lying in the float bowl! Problem solved. Still not really sure which way to turn the air screw to weaken the mixture though!

[Skorpion]

Hi stogadog.

If you have the original BVF carb fitted the air screw is turned out to weaken the mixture,
But remember this only works on part throttle, full throttle is controlled by the needle position,
Also don't forget that the fuel level in the float chamber has a big effect on (richness-weakness) as these bikes are now over 35 years old and maybe many owners, you may be well advised to spend time and to set everything up as in the works manual.

Regards
skorpion

[stogadog]

Cheers for that - it's running fine now. The richness was just from the main jet - just took a decent thrashing to work it out! I have already checked the float height etc and that is all fine but wise words none the less!