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Special devices for tuning special carburetors setups.

It is hard when you want to be different...when you search for more horsepower...

It is appealing when everybody tells you to ditch it and go with the flow...

Introducing....

RAMAIR JETTING!!!

Oh-my-God...

This is an adventure, most will tell you, like I already mentioned, to stay clear of that, but most probably, 

others will tell to anyone who wants to listen that their recipe is the dog's bollocks...the Nirvahna...

the right thing to do...whatever I say...

Well, they are all full of crap!!!

I've tried several carburetors tuning combinations, and I can tell you that it is unbelievable how dramatically

different tuning combinations can result in the same problem...low revs stumbling.

Incidentally, they all use the plugged main air jets recipe...well, bummer...it doesn't work.

Maybe it is working for a Superbike which work 90% of it's time past 8k rpms, but for us, street riders,

it just plain sucks....literally.

With the plugged mains, you have to roll the throttle open smoothly and gradually at all time, or the engine  

will bog...it is a fact.

Later in this script, I will mention problems still showing their ugly faces around 6k rpms; what the hell is  

happening at that precise rpms for most of the jetting problems to go away?

Easy...

Since you are at full throttle by this time and accelerating hard, needle clip position and taper are at their 

optimum, the main fuel jets are at about 80% of their capacity, fuel pilot jets effect is long gone, fuel level is 

less important (by about 10%), point of origination of the needle taper is non-effective and carburetors 

synchronization in irrelevant.

Now check out the last paragraph; what does it tells you? 

For me, it tells that if there is a problem below 6k rpms, the culprit circuits must be the 

fuel pilot jet size (which is 100% critical right at 2500-3000rpms), the needles taper and their point 

of origination (3500-4000rpms) which are critical...

Then, there is more into the equation than just jetting;

I got my camshafts dialed at 110 intake/100 exhaust which displaced any fueling problems from their point

of origin, just as it displaces the peak horsepower rpms...plus a milled head and a slew of other things.

Can you feel a headache coming?

I don't claim to have found the perfect recipe myself, but I'm getting damn close!

So, the latest additions to my setup will be 2 Flo-Commanders which will take care of the air side of the carburetors.

I know that they will both influence each other to a certain point, but hey, I got to keep a challenge 

somewhere because I just like to work on my bike and it is a great way to learn more about those damn 

things (carburetors) even if all bikes are going EFI now.

So, without any further blathering from myself, let me tell you where I'm at with the tuning part:

Present  setup:

1- The airbox is a QBcarbon ramair system.

I'm pretty confident that I'd get similar results with an Attack or any other setup.

What I did to the box, is seal it carefully; the goal of this is to have even, constant pressure in the box at any 

given speeds and conditions...very important in order to tune the damn thing!

(Pics to come shortly)

I've sealed the top cover as well as the filter bottom part (it is a metal cage with a porous foam on it)

and the float bowls tubes holes (at the bottom of the box).

 2- The stock YZFR1 carburetors.

-165 genuine Mikuni main fuel jets

-Flo-Commander on the main air jet circuits (3.5 turns out)

-Mixture screws @ 3.5 turns out (read the precisions part)

-#20 pilot fuel jets (instead of the stock #15, that can change though)

-Flo-Commander on the pilot air jets circuits (4 turns out) AND main air jets circuits

-Lightly modified slides (not a must have)

-Plugged slides lift holes (1 hole on each slides-subject to change depending on setup changes)

-Float bowls fuel level lowered by 2mm

-Special one-offs needles (you can get ramair-specific needles now)

Results:

Harder acceleration than the other setups, easily lift the front wheel without any clutching...

all depending on temperature and conditions...the setup can be really sensible.

In fact, now instead of having the bike bog between idle and 6k rpms, 

it only has a very slight hesitation which can be rid of by setting the Flo-Commanders better.

Precisions:

The big main fuel jets are the ones creating the richness at low revs; yes, they play a part, even at low revs!

So, in order to counteract this problem, I've gone the "let's lean the bottom then" route.

hence the changed main air jets and pilot fuel jets for Flo-Commanders.

But I may have gone a bit over the line with the #20`s...the bike is now "pinging" a bit when releasing the 

clutch without enough fuel delivery. Not a real problem though, as the FC`s will take care of that!

So, taking into consideration that "pinging",  and the main features of the FC`s are equalizing fuel

 and air delivery as well as controlling and tuning the carburetors by adding/subtracting air and fuel all 

through the revs range I'm pretty confident that the end of the tunnel is at end!

One of the first thing I'll do is getting rid of the 5 degrees ignition trigger...I'll probably go with an adjustable 

Rohm performance set at -2 retard since I'm now running nitrous as well!!!

Some of my problems were related to the pilot air jets circuits and the new screw-type main air jets; 

the Flo-Commanders are taking care of the air circuits now.

Also,changing the settings on the FC`s simulate a change in the floats level,

needles height and mixture screw setting parts (read the report in the "special devices  

testing and impressions" section).

Note: The last dyno graph showed that the bike was still running a bit lean at the top and the rest of the fuel

curve looked good except for the bog zone; again, FC`s will take care of that.

And just in case that the ignition box EXUP circuit may be the culprit, I do have a nice YEC race box

waiting...that will be my first test!

Stoichiometric values in millivolts.

Use the chart below to help guide you in the right direction. The DynoTune meter displays the output of the oxygen sensor in millvolts.

Typically the meter is used for tuning air fuel ratios during wide-open throttle. You will not get a stable reading while cruising under part throttle.

Stay tuned.

(Updated 04/09/20)

To be updated with pics, corrections and more info.

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