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Old 05-06-2009, 06:15 AM   #2191
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Originally Posted by fulcrum2 View Post
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Do you use the 3rd adjustment screw on Nova carbs (on the backside) to tune the engine? If yes, what is your strategy or what do you look for if you turn this screw?
I know, the general advise is not to touch this screw and keep it flush with the carb body. But it must be there for a reason, otherwise Novarossi would only produce carbs without this adjustment, right?
Could you please shed some light on this topic?

Thanks a lot and best regards,

Stefan
The 3rd screw determines when the spraybar (3rd needle) is fully open to fuel flow. When the spraybar is fully opened is when the most fuel will be allowed to enter the carburetor. The low speed needle is inside of the spraybar until the carb is opened past 1/2 to 3/4 way in most carbs. When the low speed needle is inside of the spraybar the fuel flow into the engine is limited by itís length, and shape. The fuel coming out of the spraybar is also atomized by the low speed needle during their interaction. This affects the amount of fuel going into the carburetor, and the powerband. When the spraybar is fully opened determines when the engine gets the most fuel into the engine.

I rarely touch the spraybar, but yes it is a tuning option. On most engines this is set from the factory to a setting that works fine. If you unscrew the spraybar you will notice that as you pull to full throttle you will get more fuel earlier in the pull. You will see that plume of smoke from the engine earlier if you loosen the needle. If you screw the spraybar in you will notice that the smoke plume is later. This can cause a lean running condition if you are not careful.

I hope this answers your question. If not I will try to explain it again.
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Old 05-06-2009, 06:48 AM   #2192
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Quote:
Originally Posted by fulcrum2 View Post
@Grinder

Do you use the 3rd adjustment screw on Nova carbs (on the backside) to tune the engine? If yes, what is your strategy or what do you look for if you turn this screw?
I know, the general advise is not to touch this screw and keep it flush with the carb body. But it must be there for a reason, otherwise Novarossi would only produce carbs without this adjustment, right?
Could you please shed some light on this topic?

Thanks a lot and best regards,

Stefan
Following Uriah's explanation, I thought these one might add some more light to your question....hope it helps

AFM

Mid Range Needle

The screw inside the slide body is the low-end needle, and it plugs into the main jet, or so called mid range needle (the 'brass needle' in the opposite side, usually flush to the surface of the carb body) without obtruding it completely, to let a little bit of fuel to pass when the needle plugs into it to allow the engine to idle.

The dimensions of the main jet, or mid range needle (brass needle), its position relative to the venturi, and the dimensions, ramps and shape of the low-end needle dictates the fuel curve of the carburetor (or how much fuel enters by each cfm of air drawn into the engine at a relative carb opening).

At idle speed, the engine is controlled by the low-end needle, and how much air pass into the engine via the position of the barrel. But when you start to move the barrel to allow more air to pass, in fact, you're moving the low-end needle too, allowing at the same time more fuel to pass too. The low-end needle adjustment is critical, because the engine relies on this adjustment for its temperature control when idling in the infield of the race track (This is the zone where the engine does 90% of its work). If the top speed of the engine is good and the engine runs hot, you should generally richen this needle (open). You should see smoke coming out of the pipe when you open the throttle at low speeds.

Depending at which opening of the barrel the main jet (mid range needle) is totally uncovered, and the carburetor starts being mandated by the adjustment of the high-end needle, and how much fuel this last adjustment permits to pass, rather than being governed by the low-end needle, can be varied (and the power band of the engine too, but slightly) by screwing or unscrewing the main jet (mid range needle) and readjusting the low-end needle.

But be careful, screwing the main jet too further into the venturi can lead to mix and temperature problems, in fact, you're leaning the mid rpms, where the engine operates at partial opening of the carb, this can lead to problems and erratic operation. This is why, on almost all the engine booklets they warn you about not touching this adjustment, because it comes factory tuned to itís ideal average.

The position of the main jet, relative to the venturi also changes the position on where and how much the vortex of air that enters into the carb varies how finely the fuel is sprayed into the air that enters (fuel is converted into a mist to be burned), a drop, no matter how little it is, doesn't burn and can create many and serious problems. This last can lead up to a conrod breakage (common) or piston breakage (not common but seen some) due to hydro lock.
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Old 05-06-2009, 07:28 AM   #2193
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Originally Posted by afm View Post
Following Uriah's explanation, I thought these one might add some more light to your question....hope it helps

AFM

Mid Range Needle

The screw inside the slide body is the low-end needle, and it plugs into the main jet, or so called mid range needle (the 'brass needle' in the opposite side, usually flush to the surface of the carb body) without obtruding it completely, to let a little bit of fuel to pass when the needle plugs into it to allow the engine to idle.

The dimensions of the main jet, or mid range needle (brass needle), its position relative to the venturi, and the dimensions, ramps and shape of the low-end needle dictates the fuel curve of the carburetor (or how much fuel enters by each cfm of air drawn into the engine at a relative carb opening).

At idle speed, the engine is controlled by the low-end needle, and how much air pass into the engine via the position of the barrel. But when you start to move the barrel to allow more air to pass, in fact, you're moving the low-end needle too, allowing at the same time more fuel to pass too. The low-end needle adjustment is critical, because the engine relies on this adjustment for its temperature control when idling in the infield of the race track (This is the zone where the engine does 90% of its work). If the top speed of the engine is good and the engine runs hot, you should generally richen this needle (open). You should see smoke coming out of the pipe when you open the throttle at low speeds.

Depending at which opening of the barrel the main jet (mid range needle) is totally uncovered, and the carburetor starts being mandated by the adjustment of the high-end needle, and how much fuel this last adjustment permits to pass, rather than being governed by the low-end needle, can be varied (and the power band of the engine too, but slightly) by screwing or unscrewing the main jet (mid range needle) and readjusting the low-end needle.

But be careful, screwing the main jet too further into the venturi can lead to mix and temperature problems, in fact, you're leaning the mid rpms, where the engine operates at partial opening of the carb, this can lead to problems and erratic operation. This is why, on almost all the engine booklets they warn you about not touching this adjustment, because it comes factory tuned to itís ideal average.

The position of the main jet, relative to the venturi also changes the position on where and how much the vortex of air that enters into the carb varies how finely the fuel is sprayed into the air that enters (fuel is converted into a mist to be burned), a drop, no matter how little it is, doesn't burn and can create many and serious problems. This last can lead up to a conrod breakage (common) or piston breakage (not common but seen some) due to hydro lock.
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Old 05-06-2009, 08:09 AM   #2194
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Thanks a lot Uriah and AFM for your feedback. This is very good information, but tells me that even the most experienced engine guru's don't touch this needle. Still wondering why Novarossi continues to integrate it. It's one more thing that could cause issues.

I remember one thing from racing 1/10 touring. Witht those cars, where you can't turn the low speed needle with the lexan body on, I used the mid speed adjustment to make quick corrections to the low speed mixture. I turned the mid speed needle a maximimum of 90 degress in either direction. This moved the spraybar a bit but has the same effect as turning the low speed needle slightly.

Once again guys, thanks for your help!

Stefan
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Old 05-06-2009, 08:54 AM   #2195
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There is good reason not to mess with it. It comes from the factory with the best overall setting. Any adjustment to it will only make it worse. There are of course exceptions. Manufacturing tolerances, an unusual fuel/pipe/engine combination or really radical timing changes (mods) to the motor could cause a need for some fine tuning on the spray bar. I can almost always get a motor running properly without touching it. I can only think of two times in the last ten years that I had to make some spray bar adjustments to get a motor to run right.
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Old 05-06-2009, 12:13 PM   #2196
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Uriah, you have pm.
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Old 05-08-2009, 06:50 AM   #2197
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I just bought a new 2008 Blue head 353 Race 12 engine and it came with an extra needle and plastic inlet nipple. Are these just extra or are they different then the ones in the engine for different settings ?

I posted in the Novarossi Engine thread also.


Thanks for the help.
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Old 05-08-2009, 10:05 PM   #2198
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the extra needle is for more low end so on shorter more technical tracks if u compare it to the other one it will have a |_| rather than a \/ (sort of thing)
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Old 05-09-2009, 03:35 AM   #2199
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Uriah, are the MM353R's back in stock? I sent you an email a week ago to purchase a couple, no reply...
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Old 05-10-2009, 10:10 AM   #2200
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Quote:
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the extra needle is for more low end so on shorter more technical tracks if u compare it to the other one it will have a |_| rather than a \/ (sort of thing)
Thanks for the reply. I figured it was for different tuning, but didn't know which direction.

Also, what type of turbo plug does this engine take. regular, conical, etc. ?
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Old 05-10-2009, 10:58 AM   #2201
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Thanks for the reply. I figured it was for different tuning, but didn't know which direction.

Also, what type of turbo plug does this engine take. regular, conical, etc. ?
of course turbo plugs.
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Old 05-13-2009, 08:51 AM   #2202
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why arent there any m353r listed on the website?? and also what do you mean by full ceramic, since the engines come with ceramic bearings from the factory?
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Old 05-13-2009, 09:41 AM   #2203
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why arent there any m353r listed on the website?? and also what do you mean by full ceramic, since the engines come with ceramic bearings from the factory?
Don't cry. Something new is coming soon.

The full ceramic has front, and rear ceramic bearings.
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Old 05-13-2009, 12:26 PM   #2204
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oh yeah dont tell me such things sooo sudenly.... uriah
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Old 05-13-2009, 04:00 PM   #2205
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ok uriah you cant do that to us, whats new and when is it coming out? I guess ill have to get ready to spend more money! LOL
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