Zizu

I'm confused on how to tune engines with 3 needle setup.I understand how to tune low needle and top end.But how do you guys adjust the 3rd needle.Also what temp do you guys look for when using a temp gun.Thanks in advance

kn7671

iTrader: (16)

On a 2-needle carb, the needle you normally adjust for idle and mid-range, becomes mainly a low to midrange needle, while the 3rd adjustable needle is for idle only. It's not a huge change, but it does allow for better response when you get on and off the throttle on tight tracks.

I think some or most carbs have a 3rd needle already, its just that they are not adjustable, which means you have to rely on the midrange and high needles to get what you want.

popsracer

On a slide carb, the 3rd needle is used for mid range mixture adjustment. It will be exactly opposite the low mixture needle.

Since these needles usually fit into each other, a mid range adjustment will also effect your low speed mixture. It can be very tricky to get the right balance of settings if you adjust the mid range needle and this is why most manufactures tell you to leave it alone unless you are an experienced engine tuner.

ND

If your running a Nova Rossi engine with a three adjustment carb you should try not to adjust the mid range jet, if you do need to adjust it you should only really move it half a turn in either direction from the factory setting.

Gped0124

I look for between 210-220 when temping my engines, just to answer that question.

Im2lazy

I don't really pay much attention to the temps of my motor as much as performance. If you are really at a loss, and are really worried about your engine temps, check with some local racers that have engines that perform well and don't flame out about the temperatures at which they normally run.

I usually am around 240-270 - that's conservative, but not overly-so...at least in my opinion. If you want more responses about the temps most people run at, just do a search... you'll find loads more answers.



And if you're asking how to tune the mid-range needle, I don't think I'd suggest tuning it.
But just like others said, it affects the low-range adjustment too, so any adjustment made to the mid-range needle needs to be compensated for by the low-end adjustment as well.

The Sleeper

I don't claim to be a expert but this is what I believe the 3rd needle is.

First off, it isn't a needle,,, it's a jet. A jet is a small tube that delievers the fuel into the carb throat. When air flows down the carb and passes the jet, it sucks the fuel along with it. Not only does the air pull the fuel, it atomizes it too. It is critical that the fuel be atomized (or made into vapor) before it will burn. Also critical is the position of the jet inside the carb throat. If the jet is too far inside the carb, air will simply blow pass it and not pick up any fuel. If the jet is not far enough inside the carb, air might pick up fuel but it will be in droplets and not in vapor. So by adjusting the "3rd needle" you are adjusting the position of the jet inside the carb and subsequently how well the fuel will be atomized.

It's best to leave the 3rd needle alone.

mtx3racer

don't ever mess w/ the mid range. Its always at a pretty good setting, it should be flush w/ the edge of the carb. The low and top are the only only to mess with

Zizu

Been away for quite awhile.Thanks guys for the feedbacks.Reason I ask about the 3rd needle was because I took my Novarossi RS12T5 apart for cleaning.Now it doesn't as well as before.I'll do what mtx3racer says.Make it flush w/the edge and see if it'll do the trick

sparksy

iTrader: (14)

The 3rd needle can be used as an alternate way to "fine" tune your lowend. It is not a needle, as said before, it is the jet thet the low end needle seats in. So if its ackward to reach your low end needle when you have your body on... and you want your pitman to tweak you lowend a little, dont be scared of using it..... a little.

one turn in on the 3rd needle is the same as one turn in on the low.

Adjusting the 3rd needle in conjunction with the low end also moves the midrange powerband. For example... if you screw the 3rd out one full turn and the lowend in one full turn... your going to have the same lowend adjustment, but as you open the throttle, the needle will clear the spraybar sooner.

Dont be afraid to play with it... and its easy to reset it to factory. Flush with the outside is factory.

Fisher890

ok this is starting to look clearer in my mind as to what does what. The Low end needle and the spray bar should be adjusted so that they are very close to one another as to atomize the fuel as much as possible? leaving a gap causes more bigger drops which is Bad right?If I were to need to run leaner on the low end I should also compensate the Spraybar so that i don't have needles touching and voiding the adj? Or is there an acceptable gap between the two?Please bear with me I'm just starting to get a glimmer of what i want to see in my mind. And at the same time Get a sound for it in my Ear because my temp gauge is garbage that needs to be thrown a million miles or something like that.....

Pyramid

If those numbers were in Celcius, I will be wondering how long it takes for me to properly tunes the engine. jokes

The Sleeper

I really wish Motorman or Grinder would answer this thread. They're the experts. But I will try to help.

Not exactly. The air rushing down the carb is what atomizes the fuel. Think of blowing compressed air across the end of a garden hose. You get a fine mist of water right? The same thing happens inside the carb only it isn't water, it's fuel.

Leaving a gap is bad yes, but not because of bigger drops. If the gap between your low end needle and spraybar is too great, then your engine would run rich. The low end needle only regulates how much fuel can enter the engine at a idle. Only the position of the spraybar will determine whether the fuel will be in as mist or in as droplets.

No you do not have to compensate the spraybar. Really you shouldn't have to move the spraybar ever at all. If you were to lean the low end needle and then backed out the spraybar, your low end setting would still be the same. That's because you didn't reduce amount of fuel that can enter the engine.


Have I got you totally confused yet?

popsracer

Guys;

To adjust the Mid range, you need to move BOTH neddles in the SAME direction. This changes at what point in the opening of the slide, that the needles start to seperate and thus effects the mid-range mixture.
If you were to adjust the Mid range needle only, this would have the same effect of adjusting the low speed needle.

The proper adjutment proceedure is to first adjust the High speed needle (mixture), then the Low speed needle, then adjust the Mid range needle AND the Low speed needle in the SAME direction, so that their relationship to each other does not change.

Clear as Mud?

Marcos.J

iTrader: (239)

Carburetor adjustment


The carburetor on the NovaMEGA engine is preset at the factory, meaning that the original settings are close to where they should be for normal operation.




The NovaMEGA carburetor has 3 adjustments:
1. Main needle: controls the amount of fuel at all RPM
2. Low speed needles (front and rear): control the
amount of fuel at idle and low RPM
3. Idle adjustment screw: controls the idle RPM with
the carburetor closed







The most difficult thing to adjust is the low speed adjustment. Keep the following principles in mind when doing this:
· Use the idle adjustment screw to adjust the idle RPM
immediately after closing the carburetor
· Use the low speed needle to adjust the fuel mixture
2-5 seconds after closing the carburetor
· Use the front low speed needle (at the front end of
the carburetor slide) for basic adjustment (off the
track)
· Use the rear low speed needle (at the rear of the
carburetor body) for fine adjustment (on the track).
Use only a ½ turn each way.




The "Golden Rule Of Carburetor Adjustment" is to make only small adjustments at a time, maximum 1/8 of a turn, especially when fine-tuning. The engine is very responsive to small changes in mixture settings.