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Old 05-22-2010, 05:32 PM   #16
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Steve,

the S21 BK EVO4 STI does have a brass allen head kinda flat spray bar adjuster on the side, i will get a side pic of my engine later.. the pic that i posted is too small to see it..

rasteinberger; check for air leaks and some engines will do that if it is too rich on the bottom.
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Old 05-22-2010, 05:37 PM   #17
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That's not an adjustment. That's a spray bar in a 2-needle carb that's meant to be screwed in and stay there. If you loosen it and try to use it as an adjustment, then you're going to have one heck of an air leak. ;o)
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Old 05-22-2010, 06:03 PM   #18
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Lean it till the rpm dont change then lower the idle where you like it then you should be fine.
Cool thanks, i will try it in the morning. i really appreciate everything. what about the spray bar then? is it in fact adjustable some how, or no and just tighten it down?
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Old 05-22-2010, 06:22 PM   #19
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Here's a picture of the carb D8 is talking about. If your carb looks like this, the part that's tightened with the allen wrench is meant to be tightened down and left alone. That's not an adjustment. It has O-ring seals as well, but the moment you crack it loose to make an "adjustment," you take one of the O-rings out of the equation and you're sure to have an air leak, big or small. It's simply not designed or intended to be adjusted.



The picture below is of a Sirio 3-needle carb. Note the slotted brass screw in the side of the carb. This IS designed to be adjusted. Both of the O-rings are deep in the bore and they can accommodate movement of the spray bar without leaking (usually). Both carbs use the same body, but one is clearly not intended to be adjusted and the other is.




If your spray bar is not the adjustable type, then you definitely don't need to worry about it, but even if it is, leave it alone. If necessary, adjust it so it's somewhat close to flush as shown here. Make all the low-speed adjustments on the other side of of the carb where the linkage attaches. That's your low speed needle.

Your answer to my last question tells me that your fuel mixture is too lean on the main needle. The reason I ask is, when the main needle is too lean, the engine will run on when you let off the throttle. After a few seconds of running at idle with an OK low-speed setting, the engine will start to get the right amount of fuel and the engine will idle down. So, start by making the main needle more rich and see what happens. Don't worry if the engine is a little sluggish right after starting - this is normal. When the engine warms up it leans out naturally, so perhaps you tuned it when it was cold or not up to full temperature and it's a little too lean on the high speed needle.

FYI - some carbs have black oxide steel needles and spray bars, and like these, some are made from brass. It makes little difference - they're pretty much exactly the same.

Last edited by SteveP; 05-22-2010 at 08:31 PM.
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Old 05-22-2010, 07:58 PM   #20
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Cool thanks, i will try it in the morning. i really appreciate everything. what about the spray bar then? is it in fact adjustable some how, or no and just tighten it down?
Thanks for everything, i will see how it goes. my last point on the settings on the carb was 3 9/12's on the high and 6 1/12 on the low. so it sounds like i have at least a low out of adjustment. thanks again, i will let you know how i make out.
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Old 05-22-2010, 09:00 PM   #21
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Steve,
the manual says that the spray bar adjuster sets the engine torque under normal engine running conditions... and like and any other 3 needle engine it tells you to leave it alone unless you are an experienced user.. I use the spray for some fine tunning at times and it does work as an adjustment..
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Old 05-22-2010, 10:23 PM   #22
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Steve,
the manual says that the spray bar adjuster sets the engine torque under normal engine running conditions... and like and any other 3 needle engine it tells you to leave it alone unless you are an experienced user.. I use the spray for some fine tunning at times and it does work as an adjustment..
I looked mine over and it is safe to say that I do not have the 3 needle adjustments. So no need to worry there lol. Mine is just the hex head that would appear to just tighten. So I will be trying to do the adjustments that was recomended earlier then. Thanks again.
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Old 05-22-2010, 11:17 PM   #23
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the adjuster on my sirio feels pretty tight., hard to move with just fingers... do you have the black engine block or the silver one? i have the black and it is actually different than the silver block engine, my friend has the silver block engine and a few parts are different than my engine.
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Old 05-23-2010, 12:00 AM   #24
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Steve,
the manual says that the spray bar adjuster sets the engine torque under normal engine running conditions... and like and any other 3 needle engine it tells you to leave it alone unless you are an experienced user.. I use the spray for some fine tunning at times and it does work as an adjustment..
It's honestly not my intention to argue with you - I was just trying to help rasteinburger. But, telling someone that this is an adjustment is incorrect and I wanted to at least make it known that it's a really bad idea. I'll spare you the long version, but lets just say that I was involved in the distribution of the Sirio engines for about 3-4 years. I've rebuilt hundreds of these carbs and still have a box of about 2 dozen carbs that were taken off worn-out or broken engines. I built many of these carbs for Joel Johnson, Cody King, Ryan Lutz, Ryan Cavalieri and MANY customers at the track who needed help.

Below is a parts list for Sirio carbs. You'll notice that it refers to a single adjustment and a double adjustment carb. The Italians don't count the main needle, so a single adjustment carb (the one you have) only has an adjustable low-speed needle and a fixed spray bar. A "double" adjustment carb has an adjustable low-speed needle and spray bar, just like the second of the two carbs shown above. You'll know that it's a single adjustment carb because it comes with an 8.5mm slide valve. The double adjustment carbs came with a 10mm slide valve. FYI, I found the engines run much better with the 10mm slide than the 8.5mm slide. In spite of using the same size restrictor in both carbs, the 10mm slide really tuned better and the engine would come out of the corners noticeably stronger than when using a carb with a 8.5mm slide.


Trying to use the "fixed" spray bar to adjust the fuel mixture, which I'm not sure you could have done in spite of insisting you have, is like loosening the glowplug to adjust your compression. The outer O-ring on the fixed spray bar is simply pinched between the big flange on the spray bar and the carb housing, and it's the only thing that seals the fuel into the carburetor. If you loosen it (which is the only way you can turn it), fuel will simply leak out of the carb and you'll have a giant air leak as well. So, continue to use it as an adjustment at your own peril, but anyone reading this should never use this as an adjustment - unless you like fighting fuel and air leaks. ;o)

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Old 05-23-2010, 12:17 AM   #25
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the adjuster on my sirio feels pretty tight., hard to move with just fingers... do you have the black engine block or the silver one? i have the black and it is actually different than the silver block engine, my friend has the silver block engine and a few parts are different than my engine.
I have both. Apart from changing the material from steel to brass, the carbs on both generations of engine are identical. You'll notice that they've since gone to a cast aluminum carb instead of composite, and the single adjustment carb (their name for it) no longer has the removable spray bar - it's simply machined into the housing now.
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Old 05-23-2010, 01:54 AM   #26
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a lot of good info there... and i am not arguing with you at all., i am just putting out there what i've done with the carb and what the Operation and Care Manual says about the spray bar.... i treated the same way i do my v-spec engine carb., there is also another local guy that runs with me and has an trinity extech2 engine with one of this carbs and he has also used the spray bar hex screw for some fine tunning on crazy weather days.. i am also talkin about very small changes to the spray bar..
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Old 05-23-2010, 02:16 AM   #27
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a lot of good info there... and i am not arguing with you at all., i am just putting out there what i've done with the carb and what the Operation and Care Manual says about the spray bar.... i treated the same way i do my v-spec engine carb., there is also another local guy that runs with me and has an trinity extech2 engine with one of this carbs and he has also used the spray bar hex screw for some fine tunning on crazy weather days.. i am also talkin about very small changes to the spray bar..

are we talking about leaks?
cause there is something wrong with this engine and the mugen mbx6...same problem...and center crack right under the bottom of the block...maybe it happening with your car as well..maybe
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Old 05-23-2010, 07:25 AM   #28
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the adjuster on my sirio feels pretty tight., hard to move with just fingers... do you have the black engine block or the silver one? i have the black and it is actually different than the silver block engine, my friend has the silver block engine and a few parts are different than my engine.
My Evo 3 is silver and my Evo 4 is black. The carburators look different as well, but have the same number of screws for adjustments.
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Old 05-23-2010, 11:57 AM   #29
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I have both. Apart from changing the material from steel to brass, the carbs on both generations of engine are identical. You'll notice that they've since gone to a cast aluminum carb instead of composite, and the single adjustment carb (their name for it) no longer has the removable spray bar - it's simply machined into the housing now.
I really appreciate all the good info, thanks. I tried to take out the standerd needle and install the turbo needle that went fine, but i noticed that the carb keeps sticking and does not move freely. I swaped it with the carb out of my evo 3 and changed that one over to a turbo needle as well. So I am going to see how that goes now in the morning. Any concerns or cautions there?
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Old 05-23-2010, 11:57 AM   #30
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My Evo 3 is silver and my Evo 4 is black. The carburators look different as well, but have the same number of screws for adjustments.
I really appreciate all the good info, thanks. I tried to take out the standerd needle and install the turbo needle that went fine, but i noticed that the carb keeps sticking and does not move freely. I swaped it with the carb out of my evo 3 and changed that one over to a turbo needle as well. So I am going to see how that goes now in the morning. Any concerns or cautions there?
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