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I just bought a Vstar 1100 and by what i was told it has cobra pipes...not really sure ...but it back fires quite a bit and loud , im concerned its gonna catch too much attention from the cops.....what can I do to get rid of the backfiring or minimize it?... any tips will be appreciated ...thanks:):D:eek::eek:
 

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Bought my 1100 a few months ago and had the same concerns.
It seems people install aftermarket pipes and dont realize the consequences

I have learned a lot from this site and the wiki knowledge base

Here is what i would suggest
Since the exhaust has been opened up, buy an air intake kit and get rid of the stock sytem.
You will then need to rejet the carbs
You now have more air and fuel to balance out the exhaust, and more power
Sync the carbs
Remove the AIS

i did all the above in the last couple weeks, and its like a new bike, plus no more popping or backfiring!!
Just do some searching like i did. Its really not that difficult.
 

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I just bought a Vstar 1100 and by what i was told it has cobra pipes...not really sure ...but it back fires quite a bit and loud , im concerned its gonna catch too much attention from the cops.....what can I do to get rid of the backfiring or minimize it?... any tips will be appreciated ...thanks:):D:eek::eek:
First you need to check for exhaust leaks, especially on the front head and where the mufflers bolt on. If that doesn't get it, then you need to turn the pilot mixture screws out another 1/2 to 3/4 turn on both carbs. Anything else is just a bandaid for improperly set mixture screws. You can do all that stuff mentioned above too......but it's not necessary to stop a backfire on decel.
 
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Discussion Starter · #4 ·
First you need to check for exhaust leaks, especially on the front head and where the mufflers bolt on. If that doesn't get it, then you need to turn the pilot mixture screws out another 1/2 to 3/4 turn on both carbs. Anything else is just a bandaid for improperly set mixture screws. You can do all that stuff mentioned above too......but it's not necessary to stop a backfire on decel.

So messing with the pilot screws wont stop the backfiring??....how would I know if my exhausts have a leak??....the bike has both aftermarket exhaust and air filter (one of the chrome cone looking ones), but the last guy i bought it from could not tell me if it was rejetted....will the bike mess up with the biackfires?....
 

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So messing with the pilot screws wont stop the backfiring??....how would I know if my exhausts have a leak??....the bike has both aftermarket exhaust and air filter (one of the chrome cone looking ones), but the last guy i bought it from could not tell me if it was rejetted....will the bike mess up with the biackfires?....
You need to research backfiring. It's not the end of the world and in some cases can't be tuned out completely. Take mine for example. Running a homemade straight pipe exhaust and its drag strip loud. Plenty of crackling and popping but there's not much I can do to quiet it without taking away from the performance side. I have a diy BAK too and it all runs great together. In your case you can prob tone it down a bit but may find its just the nature of the beast with intake/exhaust mods. Could always go back to the lame stock exhaust. Also...the cops? A: they bother you for that where you're at? B: who cares lol?

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Oh but if it were during acceleration or while cruising THEN you'd have an issue for sure. On decel/downshifting its more normal.

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Discussion Starter · #7 ·
You need to research backfiring. It's not the end of the world and in some cases can't be tuned out completely. Take mine for example. Running a homemade straight pipe exhaust and its drag strip loud. Plenty of crackling and popping but there's not much I can do to quiet it without taking away from the performance side. I have a diy BAK too and it all runs great together. In your case you can prob tone it down a bit but may find its just the nature of the beast with intake/exhaust mods. Could always go back to the lame stock exhaust. Also...the cops? A: they bother you for that where you're at? B: who cares lol?

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Im in southern California, cops are kind of douches out here.... not so much for the loudness of the pipes im worried about, but more of how loud the backfires are, almost like gun shots... LOL :D:D:D .... so if Im runnin aftermarket pipes and after market filter, i should definitely remove the AIS right??.. if so, how difficult is it to remove?.. :confused::confused::confused::confused:
 

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So messing with the pilot screws wont stop the backfiring??....
I think you need to re-read my post. I said that you need to adjust the PMS to stop the backfire on decel. If there are no leaks, a lean condition at idle is what causes it.
 

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You need to research backfiring. It's not the end of the world and in some cases can't be tuned out completely. Take mine for example. Running a homemade straight pipe exhaust and its drag strip loud. Plenty of crackling and popping but there's not much I can do to quiet it without taking away from the performance side. I have a diy BAK too and it all runs great together. In your case you can prob tone it down a bit but may find its just the nature of the beast with intake/exhaust mods. Could always go back to the lame stock exhaust. Also...the cops? A: they bother you for that where you're at? B: who cares lol?

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Yup...on a fuel injected bike there's not much you can do...on a carbed bike, all you need is to tune the carb for the set up....$20 and a screw driver is about all you'd need in a worse case scenario....and a little tuning knowledge.....and you can make it almost all go away if you want. But most enjoy a nice cackle....
 
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Ok, so I have a 2012 fuel injected vstar 950.

Slip on vans and hines exhaust
Cobra Fi2000 powrpro furl manager

no air intake mods yet

Back fires on decel and because I have fuel injection there isn't much of anything I can do?

Would an air intake upgrade reduce or eliminate the back firing?

Sorry to jump on this topic being so old and it being fguzman0707 original post but looking for help and ideas. I havent had my valves adjusted yet but if they were the culprit it would back fire idle, accel and decel right?
 

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On fuel injected bikes, the backfiring is caused by what is called "fuel cut". Above a certain RPM when you let off the throttle fuel is completely cut to the engine. This is done for EPA reasons. When the exhaust leaves the cylinder, it is still burning air and fuel as it passes through the exhaust. When fuel is cut, it causes the exhaust burn to lean out and pop or backfire to to the leaner conditions.

Most people end up with some sort of fuel control or FMS. These however don't stop the fuel cut. All a FMS does is tell the fuel injector to stay open longer than the ECU tells it too, this in turns enriches the air fuel mixture so that it is a richer exhaust burn so when fuel cut occurs it is not so lean, but it is not perfect and you will have the same backfire and popping issues just not as often.

Turning fuel cut off in the ECU is the only way to stop this. And the only way to do that is have the ECU re-flashed, and one guy does this and it has other big benefits. Ivan's Performance Products

Here is a write up I did a while back on ECU and FMS units.

Differences between ECU and Tuners.


The ECU is the brain of the engine, it controls fuel, ignition, and monitors and has diagnostics. For now, let’s look at fuel and ignition.
Fuel maps are developed for all throttle positions, RPM, engine load, mixture setting requirements, air intake, etc. These maps are setup based on how the engine was intended to operate.
Ignition Timing is also controlled based on engine load RPM, throttle position and other variable.
The ECU is programmed based on requirements set buy the manufacture. With today’s EPA standards, the mapping is setup for emissions, and economy. Since motorcycles don’t have full blown emissions systems like cars. This makes the performance and readability undesirable. Also to make things worse, motorcycle ECU’s are limited on the real time adjustments they can make, so they cannot adjust adequately for modified intake and exhaust systems. This is where the tuners come in.

Tuners: Tuners were developed for 2 reasons, to try and smooth out the readability issues with stock ECU programming, and to enrichen the A/F ratio when adding air and exhaust. The simple tuners like Cobra and EJK (no maps) simply add fuel. The ECU normally sends a voltage to the injector to open it. This is typically called the injector pulse. Tuners are placed between the ECU ad injectors. When the ECU commands a “pulse” the Tuner tells the injector to stay open longer thus enriching the mixture. The tuner is simply increasing the injector pulse longer based on the ECU ratio. This helps immensely, but is not optimal because the tuners is simply following the ECU mapping but with a richer mixture. One big misconception: ECU units do not see the tuners or know they are even there. That is because with the fuel tuners, with O2 connections, the O2 connection on the tuner Lies to ECU into thinking that the lean mixture setting is still present. This prevents the ECU from trying to constantly lean the bike out when the tuners add fuel. That is why these tuners work better with O2 connections, to keep the ECU from trying to fix the richer setting.

Jacks O2 mod: Jacks O2 mod simply lies to the ECU and tells it that the mixture is too lean, the ECU responds and very slightly enriches the mixture, it helps but is far from optimal. But works for most who are on a budget. But this only works in the 500 to 4000 RPM range, which is where V Twins pretty much operate. But even though it is richer, it is still a lean mixture.


Ignition Timing directly effects power. Ignition timing refers to when the spark plugs are ignited. In engine 101 class we learn that the spark plug ignites the A/F mixture at the top of the compression stroke (TDC) top dead center. At very low RPMs it is acceptable to fire the spark plug fairly close to TDC. As RPM increases the piston actually is moving fast enough that it is running away from the combustion of the A/F mixture. This means when max cylinder pressure is achieved, the piston has already moved to the bottom of the travel therefore has nowhere else to go but up. This results in a loss of power. So as RPM is increased ignition timing is increased so the spark plug fires before TDC igniting the A/F mixture prior to TDC, of course this means the piston is working against the A/F combustion, but the fuel burn is not instant, it actually takes time. This means the piston still has a way to go down when max cylinder pressure is reached taking advantage of the pressure so that it is still pushing the piston down.
If the timing is advanced too much, this means max pressure will occur when the piston is fairly still high in travel meaning the area for combustion is small. This results in intense heat and then leads to the A/F mixture exploding (detonation), not burning. This results in high cylinder head and piston temperatures which results in engine damage. So there is a range of timing settings that are acceptable.
On our stock bikes the timing does advance as commanded by the ECU, but it is not advanced enough for power, instead it is a compromise to be delayed enough that the A/F mixture is still burning during the exhaust stroke, this is intended to keep the exhaust temps high to keep the catalyst converter hot so it works effectively.

So on our stock bikes, the A/F ratios, fuel mapping and ignition timing are not at all optimized for performance and ride-ability. Instead they are optimized for emissions.

So Ivan’s ECU flash corrects all the parameters that regulate fuel mapping and ignition timing. But since our ECU units are limited on sensor data, they cannot recognize open air or exhaust, so that is why we still need a fuel tuner if we want to maximize performance. But since the tuners follow the ECU, a optimized ECU makes all the difference.




 

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I just bought a Vstar 1100 and by what i was told it has cobra pipes...not really sure ...but it back fires quite a bit and loud , im concerned its gonna catch too much attention from the cops.....what can I do to get rid of the backfiring or minimize it?... any tips will be appreciated ...thanks:):D:eek::eek:
Hello my friend. I just bought a 2004 vstar 650 custom with vance ,hines after market pipes. I'm pretty sure your recommendation need to adjust the PMS to stop the backfire on decel. is my prpb but its my 1st yamaha and i sure wish you could explain like im a 9 yr old how to do this. or a video. It runs a tad high at idol esp warmed up and we def get some popping on deacceleration. Could you help me ? Thanks a ton if you can. Cheers vstar650 guy.
 
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