Which way to turn!

[Feasty]

I've got a Yamaha SR125 but am still not 100% sure which way to turn the mixture screw underneath the carb to make it leaner or richer. Anyone any ideas?

I've always assumed undoing (anticlockwise) makes the bike run leaner, even the Haynes manual I have doesn't make it very clear which way to turn...

[feef]

my assumption is that undoing the screw will richen the mixture..

====<//////

un screwing it will have this effect

==== </////

making the gap between the point and the jet bigger, so allowing more fuel thru

a
____________________
Mudskipper wrote: feef, that is such a beautiful post that it gave me a lady tingle
Windchill calculator - London Bike parking
Blog and stuff - PlentyMoreFish dating

[Feasty]

Hmm, that may explain a couple of things! However, I've tried turning the screw a couple of turns one way and the other whilst the engine is idling and it makes no difference... I'll have to have another look tonight now I know which way to turn it!

[Pete.]

Idle mixture screws need adjusting 1/8 of a turn at a time. If you turned it 2 turns then you have some other problem, unless it was already turned too far out and running as rich as possible.

Also, a lot of people don't realise that the adjustment screws only affect very low-speed running. It won't affect the main mixture or help with fuel economy much at all. The biggest effect on fuel economy is needle height imho.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[KatOwner]

Also, you need to be sure what you are trying to achieve.

The mixture screw you are adjusting only really has an effect at tickover up to about quarter throttle. For mid and top range running, you need to look at the needle position and main jets.

You don't say what you are trying to do when you alter the setting. If the bike is not running right, then you may need to do more than adjust the idle screw....especially if you are not seeing anything change when you alter the setting. Last time I set up an idel screw on a single carb bike, half a turn went from not idling at all to idling too fast..... correct setting was about 1.5 turns out from fully in. Varies from bike to bike.

[Feasty]

I was having specific problems that I've now solved, however this is something that has been bugging me for a while and I've never been 100% certain which way turning the bugger does what!

Turns out from previous posts I've been thinking it worked the opposite to how it actually does, but I still had it about 1 turn out from fully closed and that seems fine.

I was also curious as last night I had another fiddle (like you do!), and discovered I had to unscrew the screw about 4 turns before the tickover started being more erratic and eventually dying. However with the screw fully closed the bike runs exactly the same as if the screw is unscrewed by 1 turn. I'm trying to work out if this means some jets are slightly blocked etc, or wether it's just because it's a 12 yr old bike and not as responsive to changes as it used to be in its heyday!

Any ideas?