Idle air adjustment

Jimbo

If you talk the talk you should walk the walk
Depends what you want.
If you want an engine that idles nicely then set it for that.
If you want an engine that makes the most power then set it accordingly.
I hear it all the time "The idle mixture screw only affects the mixture at idle"
If that's the case then why do you set the low speed needle on a tilly so rich and tailor the performance of the kart at high speed with the high speed needle?
On a methanol carb like a Miluni why do you drill / ream the idle jet so big?
"I've never won a race at idle yet"
 
I've never race 4 cycles, but when I was racing 2 cycles, I could never get over people's fascination with making it idle. I suppose there's something to be said for letting the engine idle and warming it up, but that's not a race setting. Warming it up is okay I guess, but you're never going to race at that Temp, or RPM.
 

steve baker

Member
The idle air jet screw does have an effect on the wide open throttle air fuel ratio.Fuel does exit into the air stream thru the small hole on the floor of the venturi just behind the slide throttle valve. Turning the screw out will lean the engine out and turning the screw in will richen the engine up. Of course this has an effect on idle air fuel ratio but also as I explained at wide open throttle. If you ever hear a 206 engine sitting on grid that sounds ratty it probably has the idle air screw turned way in and or the slide needle is in a richer c-clip setting.When the idle air screw is turned all the way in this creates a very high fuel draw signal and fuel flow out the .039" floor hole!

Remember the main jet is .039" and the venturi idle fuel hole is .039" / .013" jet ...........................Hmmmmmmmmmmmmmm...got it?

As they say you don't win races on idle, but the idle settings on the LO206 engine do have an affect under race high rpm conditions.

That's the beauty of the Briggs and Stratton PZ style carburetor, it gives you lots of tuning options! Way to go team DK..........

Steve
www.Bakerracingengines.com
 
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I've never race 4 cycles, but when I was racing 2 cycles, I could never get over people's fascination with making it idle. I suppose there's something to be said for letting the engine idle and warming it up, but that's not a race setting. Warming it up is okay I guess, but you're never going to race at that Temp, or RPM.
Al I will have to give you this one. Dead on!
 

JPM

Member
The idle air jet screw does have an effect on the wide open throttle air fuel ratio.Fuel does exit into the air stream thru the small hole on the floor of the venturi just behind the slide throttle valve. Turning the screw out will lean the engine out and turning the screw in will richen the engine up. Of course this has an effect on idle air fuel ratio but also as I explained at wide open throttle. If you ever hear a 206 engine sitting on grid that sounds ratty it probably has the idle air screw turned way in and or the slide needle is in a richer c-clip setting.When the idle air screw is turned all the way in this creates a very high fuel draw signal and fuel flow out the .039" floor hole!

Remember the main jet is .039" and the venturi idle fuel hole is .039" / .013" jet ...........................Hmmmmmmmmmmmmmm...got it?

As they say you don't win races on idle, but the idle settings on the LO206 engine do have an affect under race high rpm conditions.

That's the beauty of the Briggs and Stratton PZ style carburetor, it gives you lots of tuning options! Way to go team DK..........

Steve
www.Bakerracingengines.com
Thought was the mixture screw may be a better choice for tuning than the slide needle.....
 
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