LO206 carburetor settings

Why not just set the slide height with the no-go gauge...then tighten the cap another "nth" and lock it down. Wa-la, the no-go gauge now doesn't enter and you've got max opening.
I'll agree with kart43 that flirting with an extra .001" generally is not worth the risk of a DQ. On the other hand, I wouldn't want to leave any power on the table either - I'll take every extra .001" I can get.
As engine builders, we've all done it for years - everything from restrictor plates to valve lift, from compression to stroke, from piston pop-up to combustion chamber depth, from valve seat diameter to carb bore. You get the idea. A thou here and a thou there all add up.


-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
steve baker said:
In general I agree with your calculations Al.......do you know how a 5% change in air density would affect lap times and then if you would correct the main jet to match the 5% air density change would again affect the lap times............please make that calculation for me based on a 1 mile long track with 10 right turns and 3 left turns. Im not sure what the factory tolerance is for the main jet hole size is but the Briggs rule set are ........... Main jet – #95, hole size is .0380” 0.036 go, 0.039 no go.

But for now i'm off to the local races.

Steve
Click to expand...
#95mm = .0374" A 1% change in air density would call for 1% change in jetting. That's according Longacer. A .0002" change in the hole size would be just about right with that size jet.
 
Plus or minus, .001" in jet size, starting with a .95 MM, would cover about a 10 point change in the air density. That's a big change. One of my fetishes is keeping track of the air density here in Texas, and I very seldom see, if ever, that much change in a year. Definitely not in one day. In Texas, it very seldom goes from very hot to very cold. If it's cold in the day, it's cold in the night. If it's hot in the day, it pretty much stays warm at night.
 
steve baker said:
We have been receiving a lot of calls about what are good settings for the Walbro PZ22 LO206 carb. Based on what we have found I am going to list them below as good starting points and will probably be fine for 90% of the times for Senior classes and for the green and yellow slides the only difference is we set the C-clip needle on slot #2 from the top.

Float height = .860 / .880 inch
Float drop = 1.050 inch
Idle air bleed screw = 1 turn out
C- clip needle setting = middle slot ( #3 slot )

Additional tech info from Briggs..........http://www.briggsandstratton.com/engines-racing/~/media/Racing/carbtuningguide.pdf

Steve
www.Bakerracingengines.com
Click to expand...
Steve Im in very high humidity, an heat, would the 3rd notch be good starting point down here? sw {louisiana}
 
Slot #3 will richen the carb. High heat and humidity would need a leaner mixture, not richer. I would leave it at #2. We very seldom go to the top slot.
 
I would say that most people that actually try to adjust the carb for different weather conditions do it by the hope and poke method.
Example: It's hot and humid so lets make an adjustment.
They really have no idea what the air density is and may actually be hurting themselves.
 
^ correct.

I'd go a step further and say that if your engine was not dyno tuned with your air density gauge in the dyno cell, you have very little knowledge of where to start tuning at. (ie What was the A.D. -on your gague- when your engine was properly tuned on the dyno?) How does your builder's A.D. gauge compare to yours? If his gauge reads 95% and yours reads 98% -- you may be making incorrect decisions on tuning based on your starting point.
A portable lambda (air fuel ratio) gauge may be a better solution; or better yet, gather as much data as you can, and start to build a database to tune from.
I remember a race @ Daytona where a particular builder brought his dyno to the track. How serious do you want to get about tuning?
 
gary10 said:
And how much does it actually matter? I haven’t changed my carb settings at the track in two years or more.
Click to expand...

Generally we're talking about halves of tenths, Gary. You know, if the engine was set up right and tuned from the builder, making small carb changes (clip on the needle or float height) is not going to take a guy from mid pack to the front even in extreme weather conditions.
Now, not that I discourage racers from learning to tune, but it's a little more involved than if the air feels thinner that day to lean the carb a notch on the needle.
Also, don't go by corrected barometric pressures offered on the the local weather channel.

Again, although this engine package and classes appeal to many, tuning isn't for everyone.
Focus on driving and chassis - the built-in engine parity is a great equalizer.
 
I have ? on the slide. Where are you measuring from? I have the black slide and it goes all the way up past the carb bore. Where are measuring 0.440 at? Or am I looking at something different. I looked at a few videos and they show sanding the cap. That would let the slide go up farther. Could someone please explain this to me. Thanks
 
You must log in or register to reply here.
Back
Top