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Discussion Starter #1
Hey all, I have a 2015 XG750 that I bought last year from the original owner. When they bought the bike from the dealer they had quite a few things added to it including the screamin' eagle performance air cleaner and nightstick exhaust.

Does this setup benefit from a tune being done to it? Is it possible that the dealer has already done this tune - or is there a way I can check for it? I have tried contacting the dealer for more information on the initial purchase/installation of the parts but they aren't keen to sharing since I am not the original buyer... ugh.

Thanks in advance!
 

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2016 Harley-Davidson Street 750 in Sunglo Velocity Red
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To be honest, a brand new bike can benefit from tune. The factory tunes them leaner than most riders would prefer because in order to balance performance and tail pipe emissions. I figure I've already reduced emissions by 75% compared to driving my truck, so I'm good with throwing away some of those gains for improved rideability and performance.

When a free flowing exhaust is put on the bike it is going to help to more thoroughly evacuate the exhaust gasses from the cylinder. There are some minor gains to be had by retuning the bike for optimum performance, but nothing earth shattering. Just adding the exhaust without a tune isn't going to lean out the mixture so much as to do engine damage or require a tune to make the bike rideable.

By the time a free flowing intake has been added the mixture is leaned out enough that you can start burning valves. In some cases the fuel/air mixture is off enough to impact rideability. If the engine seems to be hard to start, lags when you get on the throttle, but maybe performance improves once the engine is warmed up I would suspect it is running lean.

Some quick takes:
  • No H-D service department write up guy would have missed the opportunity to charge another couple of hundred bucks to tune the bike when all of those parts went on it.
  • The service department should be able to hook up the computer and read the ECM.
  • Check under your left side cover. If you are really lucky the previous owner left a Fuel Pack 3 or similar tuner attached to the wiring harness. That way if you change to another intake or exhaust you can update the tune with the same device you already bought.
  • I believe the H-D service techs would most likely have used the Screamin' Eagle Tuner, which is a leave behind unit. That way it's a charge to do the tune again if you change anything.
 

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The bike cannot be tuned without the software package such as a V&H Tuner. Now here is the problem. Once the tuner has reprogrammed the bike, you can technically remove the tuner, and a new buyer would not know what the deal is. With all the aftermarket parts (exhaust and air inflow) it is highly desired to tune the bike to those settings. I assume you would be able to tell if the performance is not peaked - in that case the tuning is needed, I guess that if it runs ok, that you are good to go. You may want to call V&H and ask them if a reprogramming is possible with another flash if you dont have the original tuner because once flashed, the computer is "married" to that tuner ID. Good luck!
 

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2016 Harley-Davidson Street 750 in Sunglo Velocity Red
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Edgar is correct that tuning requires software and hardware. Some units like the V&H Fuel Pack 3, the tuner that I have used, are stand alone devices. They plug into the wiring harness on your bike and connect over Bluetooth to Android and/or IOS apps for user input and output. Others, like the H-D Screamin' Eagle Tuner require a separate computer and cables which vary by model of bike.

Either can be disconnected from the bike at the end of the tuning session as their only purpose is to provide a user interface to read and write values that are stored in the your bikes computer, the ECM. Some that aren't required to be attached to a laptop or desktop computer, like the FP3, may remain attached to the bike. This is to provide for additional tuning options or continuous monitoring. This function can be used to put readouts on your phone, such as a tachometer for pre-2017 Streets that have no onboard tach or a gear indicator. A couple of years ago @Gaijin used this functionality to create a simulated dyno run for his bike as explained in the thread Stage 1 upgrade results from "free" dyno.

The tuner will check the VIN of the bike that you have it attached to and write that value to the tuner permanently. Any tuner sold to consumers will be able to save a limited number of VIN's and thus will work only with those specific bikes. Most tuners only have one VIN slot, so only work with the first bike to which they are attached. There are a few tuners, like the TTS MasterTune Dual Bike Kit, that will work on more than one bike but still only a limited number. A dealership or independent shop that offers dynamometer (aka dyno) tuning has a similar device without such a limit, but those don't come at a consumer friendly price.

In short, the consumers grade tuners are devoted to one bike but the bike is willing to see other tuners. Otherwise the manufacturers wouldn't be able to sell anywhere near the number of $350-$550 tuners that they do now.

Since the consumer grade tuner essentially becomes a paperweight without the bike it is married to, the owner may have left it attached to the bike. It's no loss to the former owner as he can't use it on his next bike or sell it separately to anybody else.

My bike uses the same port to plug in the tuner and the 12-volt power point on the handlebars, so I can only plug in one or the other at any time. The tuner is zip tied in place but unplugged from the electrical harness right now. Look under the side covers of your bike and you might possibly find the one used on your bike whether it's currently plugged in or not.
 

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2016 Harley-Davidson Street 750 in Sunglo Velocity Red
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Another possibly helpful item that Vance & Hines makes is the CODE: READ (6-PIN) - VANCE & HINES (vanceandhines.com). It's a code reader that just reads the ECM and doesn't actually program it. These can be used across multiple bikes and cost a fraction of what a Fuel Pack 3 costs. It can read the code that's causing an engine light or provide the continuous monitoring information to your phone.

I'm also guessing that the ECM probably stores some of the information in string form, so it may literally say that the ECM is tuned for the Screamin' Eagle intake and exhaust. Or it could give you a date that the ECM was mapped or other values that when compared to a stock tune would tip you off that the ECM was flashed at some point.
 

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Discussion Starter #7
Thank you all for your wealth of knowledge. I bought the bike from a co-worker and while I haven't asked him about it directly I'm fairly certain he wouldn't have done any tuning himself. I will need to check under the side covers to be sure though. The bike is kind of tucked away for the winter and I haven't been able to dig it out for a few weeks with other projects going on. If there is a tune on it I'm sure the dealer would have done it, and I don't think they would have used a 3rd party tuner.

How could I tell if it is tuned? After riding it for about half a season it seemed fine but I really don't know what to look for. I'll make it a point to get to it this week. If I don't see anything I'll probably go to the dealer directly and see if they could tell me more with the VIN.

If it is not tuned I think I will pursue the V&H tuner - fuel pack 3? Does that seem like a logical next step?
 

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2016 Harley-Davidson Street 750 in Sunglo Velocity Red
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If there is a tune on it I'm sure the dealer would have done it, and I don't think they would have used a 3rd party tuner.
If the dealer did the tuning they would use their own equipment unless your buddy dropped a third party tuner in their lap and told them to use it.
How could I tell if it is tuned? After riding it for about half a season it seemed fine but I really don't know what to look for.
With the upgraded intake and exhaust but no tune we would be having an entirely different conversation, one about why your bike isn't running well. You would be noticing sluggish throttle response and "decel pop", a loud popping sound when decelerating. This popping on deceleration is due to unburnt fuel being ignited in the exhaust. Decel popping is usually a sign of a lean fuel mixture but can sometimes be a sign of air leaks in the intake or exhaust systems.
If it is not tuned I think I will pursue the V&H tuner - fuel pack 3? Does that seem like a logical next step?
If you were riding it and it seemed fine it was probably tuned, so you probably don't need to go out and buy a tuner unless you do further changes to the exhaust and intake.

That being said, my only experience is with the Van & Hines Fuel Pack 3. It worked so well when I changed the intake and exhaust on my Street 750 that I turned around and got one for my Sportster when I switched from the stock filter to the K&N free flowing one. That bike already had Screamin' Eagle pipes.

I suspect the FP3 is as popular as it is around this forum because it's usually the least expensive tuner available. It also doesn't require connections to a computer. The FP3 has an autotune feature, so if you get an exhaust or intake that there isn't a stock map for, just guess something close and follow the procedures and it will get your bike running well again.
 

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Discussion Starter #9
Alright. Sorry for the hiatus - the midwest decided to go through an arctic blast and since my garage isn't completely heated it just sucked to be anywhere but inside a warm house.

Upon further inspection under both side covers I don't see any device of any kind. In fact, I think the plug that they would have been plugged into (kind of in front of and below the battery on the right side) is capped off with a rubber cap.

Also I took a trip to the dealer it was purchased from and they the ONLY service records they have in the system are unloading the bike delivered from the factory and a battery warranty service. I'm not sure what to make of this, because the previous owner doesn't recall tuning anything yet the bike doesn't seem to run too bad? - but then again this is the only HD street I have ever encountered in my life so I don't know if it is running a bit off or not.

I guess if I'm feeling rich one day I'll get a tuner. I could take advantage of monitoring tools on my phone anyway since it is a 2015 with no tach or anything like that.
 
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