for: Slide operated, non-CV carbs

Example: Engine that has redline of 13000 rpm

First, select the main jet size that makes best power over the last 3000 - 4000 rpm of the powerband.
Refer to EC997 training / 4 gas EGA tuning procedures for detail.
Do NOT tune to A/F Ratio - most slide carbs will not deliver best power or response at 13:1 A/F Ratio.

You will almost always end up with results like this
IF you have the best main jet installed.

IN PROGRESS - That's why the pilot circuit is missing.....

First: Tune Main Jet 100% Throttle - tune top rpms only
RPM	4k	5k	6k	7k	8k		9k	10k	11k	12k	13k
run quality	won't run	barely runs	maybe stumbly	runs ok	runs better		runs well	runs well	runs well	runs well	runs well
fueling	too lean to run (let off the throttle, dummy....)	just barely enough fuel being delivered to run (barely enough vacuum to pull fuel up)	way too much fuel delivered	still too much fuel delivered - better than 6k	leaning out a bit		mixture settled	mixture settled	mixture settled	mixture settled	mixture settled
f u e l  r a t e			6k
			(reversion)	7k
			(reversion)	(reversion)	8k
		5k					9k	10k	11k	12k	13k
		(too little vacuum)
	4k
	Running: disregard trying to tune this lower rpm area with main jet - it's a dysfunction of a slide carb..... (btw: needle will have no affect at full throttle here on a SLIDE carb)						Pay attention to this rpm area only for selecting best power main jet.
RPM	4k	5k	6k	7k	8k		9k	10k	11k	12k	13k

Second: Needle height / taper 75% Throttle - tune for TOP rpms only
RPM	4k	5k	6k	7k	8k		9k	10k	11k	12k	13k
run quality	might run somewhat...	probably runs ok	probably runs well	runs well	runs well		runs well	runs well	runs well	runs well	runs well
fueling	If won't run - (let off the throttle)	mixture might be settled by now	mixture probably pretty well settled by now	mixture settled	mixture settled		mixture settled	mixture settled	mixture settled	mixture settled	mixture settled
f u e l  r a t e
			6k
		5k	(maybe a bit of reversion)	7k	8k		9k	10k	11k	12k	13k
	(?? too little vacuum)	(maybe enough vacuum)
	4k
	Running: disregard trying to tune this lower rpm area - it's a dysfunction of a slide carb..... (btw: needle will have no affect at full throttle here on a SLIDE carb)						Pay attention to this rpm area only for selecting best power needle height.
RPM	4k	5k	6k	7k	8k		9k	10k	11k	12k	13k

Third: Needle height / type / taper 50% Throttle - tune for TOP rpms only
RPM	4k	5k	6k	7k	8k		9k	10k	11k	12k	13k
run quality	runs well	runs well	runs well	runs well	runs well		runs well	runs well	runs well	runs well	runs well
fueling	mixture settled	mixture settled	mixture settled	mixture settled	mixture settled		mixture settled	mixture settled	mixture settled	mixture settled	mixture settled
f u e l  r a t e
	4k	5k	6k	7k	8k		9k	10k	11k	12k	13k
	should run peachy
	Running: disregard trying to tune this lower rpm area - it's a dysfunction of a slide carb..... (btw: needle will have no affect at full throttle here on a SLIDE carb)						Pay attention to this rpm area only for selecting best power needle setting.
RPM	4k	5k	6k	7k	8k		9k	10k	11k	12k	13k

Fourth: Fuel Level (aka: float height) 25% Throttle - tune for TOP rpms only)
RPM	4k	5k	6k	7k	8k		9k	10k	11k	12k	13k
run quality	runs well	runs well	runs well	runs well	runs well		runs well	runs well	runs well	runs well	runs well
fueling	mixture settled	mixture settled	mixture settled	mixture settled	mixture settled		mixture settled	mixture settled	mixture settled	mixture settled	mixture settled
f u e l  r a t e
	4k	5k	6k	7k	8k		9k	10k	11k	12k	13k
	should run peachy
	Running: disregard trying to tune this lower rpm area - it's a dysfunction of a slide carb..... (btw: needle will have no affect at full throttle here on a SLIDE carb)						Pay attention to this rpm area only for selecting best power fuel level
RPM	4k	5k	6k	7k	8k		9k	10k	11k	12k	13k

Hint!
When jetted to make best power, you will not be surprised if you find Slide carbs will run a higher CO% number than what you are used to when optimally tuning CV type carbs or properly staggered fuel injection systems.

Most slide carbs run very dirty - as far as HC is concerned and you will almost always find extremely high HC values. Factory Pro has started to address that poor fuel state with several Keihin Flatslide carb kits - for example, the new Yamaha 250 and larger 4 stroke offroad bikes.

O2%: You will always find excessively high O2% values in properly tuned flatslides - DO NOT ever tune to so-called A/F ratios on competition carbs. It will be wrong. A 4 Gas EGA and tuned to Best Power is the optimal method.

Choose Main jet that pull the best on top -

Then needle clip position that pull best at 50% throttle / topend

Then pilot jet / fuel screw / air screw that pulls the best at teeny throttle / no load

IN PROGRESS - the following is from a European tuning shop -

 We are not experienced with this carbs and have no information about an "starting point" settings for this engine (air jet, main jet, air crew, needle position, float level etc...).

That is OK - We never assume that we know where to start, either! :-)
So - we simply start at "whatever is in the carbs". Trying to guess as to what it "should be" is going to be wrong, anyway, so we just eliminate our "best guess" as a first try.   :-D
 

 Is the synchronization procedure the same as with CV??.

Hmmm.....
I'm thinking as to what you are thinking when you ask me that.....
Nothing special - it's just that you are changing the linkage setting to adjust the synchronization.
I set the synch at 3k -
 

I´d be very grateful if you could ease some info so we can begin with the tuning procedure as with other carbs. We have inertial/brake dyno and data logger for record/real time Lambda analysis, so numbers won't be a problem.

Ok -
Sweep Test:
Junk it - it is useless for tuning, except for a "rough" idea before you actually tune - as in just to provide a customer how bad the tuning is now (as if the customer didn't already know. :-)

Steady State:
Only method to use -

Lambda values:
Good for rough tuning (+/- 10% grade), but not for final optimum tuning.
The only people who say differently are the people who sell the sensors........
...............................................................

To Rough Tune:

1. Do 100% throttle test, Steady state, 1000 rpm increments
Start at the lowest rpm that the engine will accept full throttle, end at redline, if it will go that high.
If it's close on the main jet, it will probably be 5000 to 6000 to redline.
Don't worry about how low an rpm the engine will accept full throttle - that would be like worrying about when the sun comes up! It is what it is.
I can change that a bit, but that's way past normal tuning levels.
Do NOT record anything BUT rpm's that were obtained at 100%!!!!
Example - The engine doesn't run at 100% throttle until 7000 rpm and it breaks up at 10,000 rpm -
All I want to see is 7k to 9k - nothing else -

2. Do 75% throttle test, Steady state, 1000 rpm increments
Start at the lowest rpm that the engine will accept 75% throttle, end at redline or as high as the engine will run at 75% throtttle.
If the 75% throttle tuning is proper, it will go to redline. If not correct - it won't reach redline.
The same as 100% throttle data - if it doesn't run properly at an upper or lower rpm, I don't want to see it in the test data..

3. Do 50% throttle test, Steady state, 1000 rpm increments
Start at the lowest rpm that the engine will accept 50% throttle, end at redline or as high as it will go.
Record only data at rpms where the engine runs properly.

4. Do 25% throttle test, Steady state, 1000 rpm increments
Start at the lowest rpm that the engine will accept 25% throttle, end at redline, if the engine will go that high (it probably will hit redline when it's properly tuned)

5. Do 10% throttle test, Steady state, 1000 rpm increments
Start at the lowest rpm that the engine will accept 10%, that's probably 2000 rpm if the 10% throttle settings are close to correct and it might go to 8000, 9000 or higher rpm if the 10% is properly tuned.
The better the tuning - the higher the rpm will go.

We always use Air/fuel ratios of 0.88-0.9 (12.9:1-13.2:1) at idle for racing engines (CVs). Do you recommend the same for these?

We tried using Lambda as a "Primary Tuning Target" value (and proper "Lambda" consistently did not equal "Best Power") and since then, have been the "bad guys" when people send in dyno charts with so-called "A/F Ratio" graphs and they ask us what to do - and there's no answer on what to do to get better power, based on "Lambda" - So - "Lambda" has been discarded it as primary tuning goal and have, once again, we defer to "Best Power" as the  Primary Tuning Value.
So - Tune to Best Power - NOT to a Lambda value.

One reason:
At any particular rpm and throttle position, there is no perfect "A/F Ratio"  - and optimum values change in relationship to load (throttle %)

The second issue:
Even if there WAS a PERFECT "Air/Fuel Ratio" - a Lambda Sensor based system that relies on one does NOT provide that information -
So-called "Lambda" only works 100% in a textbook - not in an internal combustion engine, where there is jet stagger that causes high residual O2 values,  improper relationship between cam timing and exhaust system, non-optimum ignition timing, ignition system power, ignition timing scatter (power commander on Suzuki's) type of fuel, combustion chamber temperatures, combustion chamber design efficiency, cam overlap, intake tract length, even type of spark plug  and on and on and on.....

All in all - tuning to an "A/F Ratio" instead of "Best Power" is absolutely guaranteed to leave power laying on the floor of your dyno room!

Use the "Lambda" readings as ONLY a "hint and clue" as to which way to change the mixture to make Best Power.
Do NOT tune to Lambda!!
That's dealership level! :-)

We use a digital 4 Gas EGA - that will provide a better picture of what is going on in the engine as far as jet stagger, ignition timing, richness, leanness -

        Any other info you consider could help us to get the most from the carbs will be welcome. We are totally rookies on these!!

Doing the Steady State Tests every 1000 rpm is super easy on our dynos - hopefully, you can do it, too - Otherwise tuning slide carbs is a horrible task.

Change the main jet to make the 100% throttle as best as it can be for power from 8000 rpm and higher.

Then send me some carb information, including float height, needle, clip position, main jet, main air jet and and I'll suggest some things for the other throttle %'s -

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