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Today I went to minneapolis' local bike tuning shop Manley Cycle and asked about what kind of carb settings they recommend for a SV. This is the response I got:

The biggest issue on SV's tends to be "the pilot air bleed circuit". Larger main jets tend to do very little unless bikes have significant mods on them. Different bikes and setups tend to run better on one shim while others prefer two. They said they haven't been able to discern much rhyme or reason as to why some bikes run better on different numbers of shims. It's just what their dyno has told them. They suggested that bigger pilots is very rarely desirable, and that even adjusting the mixture screws is generally not needed / desirable. They want $$300-$400 depending on time to sort everything out for me with a dyno. He also mentioned that desnorkeled filters and K&N filters seem to be more variable and difficult to tune for. He suggested the BMC saying it would be more predictable. This surprised me.

So here are my questions:

1) What is the pilot air bleed? How do you adjust this? He seemed to believe that this was really the big kahuna in terms of SV carb tuning (at least with just a slip-on). I want to know how hard it would be to do it on my own.

2) He suggested that adjusting pilots / mixture screw rarely fixes popping problems. Again he mentioned the pilot air bleed.

3) Is $300-$400 a reasonable price? Somewhat high?

4) Are K&N and desnorkled filters really that hard to do properly? My impression was that the BMC really did nothing over the stock filter. Is this true?

5) How does float height play into things? Can somebody provide insight as to what it does and how to adjust it ?

6) The rubber cap covering the hole for the front cylinder choke cable is cracked/loose. Could this be causing some of my rougher starts and irregularities somehow?

Right now I just have a slip-on and two shims under each needle. I was going to start by synching my carbs and then if that does not help drop back one shim on the needle. Is this the proper course of action? Thanks for helping !!! I really appreciate it!
 

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I'd like to make some comments about your post, but I'm not exactly an expert, most of what I know has been learnt through experience with my bike, so it is affected by many variables (your bike is different than mine, your location, altitude, etc). I'll start by saying that I'm not sure about 1), the pilot air bleed. I have the same question than you do, what is that? He is not talking about the pilot jet, is he?

Sarmalidu said:
2) He suggested that adjusting pilots / mixture screw rarely fixes popping problems. Again he mentioned the pilot air bleed.
Actually, I reduced -and then eliminated- the popping in my previous bike with Renegades exhaust by playing with the air/fuel mix screw (the one below the brass plug). Opening it more and more eliminated the popping on desaceleration


Sarmalidu said:
3) Is $300-$400 a reasonable price? Somewhat high?
I think that is quite high, since the guy is telling you in advance that they will not change the main jet, or the air/fuel mix, or the pilot, as those changes are not desirable. What are they going to do then? Basically, they will dyno your bike, and decide if one or two shims are right for it? Of course, the will maybe synch the carbs and adjust the ''pilot air bleed'', whatever that is.


Sarmalidu said:
4) Are K&N and desnorkled filters really that hard to do properly? My impression was that the BMC really did nothing over the stock filter. Is this true?
I don't think they are that hard to do (not if these guys have with a dyno with a sniffer). According to the people who dyno'ed my bike here in Toronto, K&N and BMC are very similar in construction, and the effect they have on the bike.

Sarmalidu said:
5) How does float height play into things? Can somebody provide insight as to what it does and how to adjust it ?
I think Wacky Woodchuck explain that on a different post, search for it.

Sarmalidu said:
6) The rubber cap covering the hole for the front cylinder choke cable is cracked/loose. Could this be causing some of my rougher starts and irregularities somehow?
Tell us more about the problems with the bike. Exactly what is the deal? Running poorly? Are the carbs stock, beside the 2 shimms? How many miles?

Cheers,

Marcos
 
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1.I think he is talking about pilot air jets,they are two of them.you can see them in funnel.I drilled my bigger when I used individual pods for filters.
2.this can come way off from factory.
3.resonable if they dial in carbs to perfection.
4.depends on filter opening.bigger hole more air and needs to be tunned for.
not hard,just work.
5.fuel level is important for whole range,0-full throttle.see factory-pro.
6.no.rubber is there to keep dirt out,not to seal.

those guys are right in saying some sv's act weird to same jetting settings other sv's work good with.
 

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Not surprising

For any given engine there are variables from one example to another. Doing the same modification on different examples of the same engine will often have dramatically different results. You could do the same modification to 10 engines and on 7 it would work, on 3 it wouldn't. There's no way to tell until you try it.

The price they quoted is not unreasonable. Figure how long they'll fool with the bike and the dyno.

What will you get? A few HP. You may get as much as 10% extra with pipes, filter and carb work. Are you racing? If not, you need to consider the cost vs. the benefit.

Lastly, there are no pilot air screws in the SV carburetor. The screws under the brass plugs are idle fuel screws. They are in the idle fuel passage between the fuel supply (the bowl) and the carburetor throat downstream from the slides. Adjusting them can have an effect at low throttle openings and under closed throttle conditions.
 
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Re: Not surprising

andyauger said:
Lastly, there are no pilot air screws in the SV carburetor. The screws under the brass plugs are idle fuel screws. They are in the idle fuel passage between the fuel supply (the bowl) and the carburetor throat downstream from the slides. Adjusting them can have an effect at low throttle openings and under closed throttle conditions.
there are two pilot air jets,just not adjustable.you have to drill them to change size.take airbox off and you will see them.one is suppling air to pilot jet where it gets mixed with fuel flowing thru pilot jet.from there this fuel/air mixture goes to pilot screw you talking about(one behind brass plug).
part of mixture goes thru by-pass hole in to carb bore right under buterfly.rest you can control by unscrewing/screwing pilot screw.
second pilot air jet goes thru diaphragm(little cover on side of carb body)and will get closed if you shot throttle to enrichen mixture and keep combustion constant.in other words it will vary fuel/air ratio to keep motor running smoother.
 

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TWF, the two pilot air screws you're talking about, one is removable (unscrews) and the other isn't, correct? Which is which relative to what you said above, i.e. which is variable?

Also, on my carbs, there is a third non-removable jet in the same area (under the funnel). What does that one do?

Thanks.
 
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Randy S said:
TWF, the two pilot air screws you're talking about, one is removable (unscrews) and the other isn't, correct? Which is which relative to what you said above, i.e. which is variable?

Also, on my carbs, there is a third non-removable jet in the same area (under the funnel). What does that one do?

Thanks.
variable is removable one.middle one is other pilot air jet and one on right is main air jet.
 
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Discussion Starter #8
Yes he must have meant the pilot air screws which would explain my confusion. I have never heard anybody refer to the "pilot air bleed". My question is this: How often do those need to be drilled out on a system that only has a slip-on? My impression was that SV's generally just need a bit on the mixture screws, one or two shims and they're set. MAYBE 140 mains up top. Am I wrong? Or is this just a "DIY not quite as experienced as a pro with a dyno so it's close enough type of setting?"


Oh, and can somebody get a little detailed as to what float height does, and how to adjust it?
 
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Discussion Starter #9
Sarmalidu said:
Yes he must have meant the pilot air screws which would explain my confusion. I have never heard anybody refer to the "pilot air bleed". My question is this: How often do those need to be drilled out on a system that only has a slip-on? My impression was that SV's generally just need a bit on the mixture screws, one or two shims and they're set. MAYBE 140 mains up top. Am I wrong? Or is this just a "DIY not quite as experienced as a pro with a dyno so it's close enough type of setting?"


Oh, and can somebody get a little detailed as to what float height does, and how to adjust it?
pipe in which main jet is screwed in can also be called bleed.air comes in to it thru main air jet and mixes with fuel.
different people call different things different names :)
unless you looking for perfection and do many mods there is no need to drill anything,like Andyauger said it may not be worth it.
float level is point where your valve closes and stops fuel flow to keep just right amount of fuel in bowl.to much is no good and to little is no good.if off/wrong it will run lean or rich everywhere.it can be adjusted by bending little ear on float that pulls valve open.this valve is what lets fuel flow oor not in to carburator.
 
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Discussion Starter #10
So basically without a dyno / sniffer float height adjustment is just guessing and not worth it?
 
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Sarmalidu said:
So basically without a dyno / sniffer float height adjustment is just guessing and not worth it?
correct.just make sure they are set at stock hight and dont worry about.
 
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Discussion Starter #12
So if I am currently running stock carbs except 2 shims under each needle and an art slip-on with stock air filter should I try to attack popping on decel by adjusting the air/mixture screws? carb sync? what should I test first? Thanks

Also I have a throttle response issue. If I go from idle to WOT while the bike is in neutral, and close the throttle right after WOT, it sometimes doesn't really rev up and makes this shuddering type of feeling. If it does rev up it makes a very angry popping as it comes back down to idle. Any idea what this may be from? The bike was properly warmed up first of course.
 
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Discussion Starter #13
I would try taking one shim out.
when you just blip throttle what rpm's do?drop down under idle rpm and than raise to idle or do they hang,slowly drop to idle?
 
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Discussion Starter #14
The tach needle doesn't dip below idle. It may be returning a touch slowly, I am not sure.

I'll try taking a shim out.
 
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Discussion Starter #15
set idle realy low and try blipping throttle and watch rpm's.
also where you live,elevation?
do you have pair valve/
 
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Minnesota. No Pair. What's the low idle / blip going to tell me?
 
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Discussion Starter #18
ok so what are the possible things that could happen and what do they indicate?
 
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Discussion Starter #19
if rpm's drop down slow it is to lean on mixture.you need to open screws more.
if rpm's drop bellow idle than come back it is to rich.
 
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