[ace.cafe]

So many EFI silencer threads to choose from!  Why not this one?

I installed my, you guessed it, EFI silencer yesterday.  Lovely idle sound, little louder than I'd like on the gas, but I'm going to live with it for awhile.  I took about a 5 mile ride, and noticed a couple of "pffft" backfires early on, then nothing until I was a block from home, when a gentle in-gear, off-throttle slowdown provided a gunshot-like report which truly startled me!  Is this ok - what kind of damage, if any, might I do if this continues?

I'd rather avoid the backfiring altogether.  I read about adjusting the TPS, but I don't wanna go there just yet.  I installed a new header gasket, and I can't feel or hear any leaks in the exhaust.  Might the EFI adjust?

This type of "backfiring" can come from being too rich or too lean in a closed-throttle position.
Typically it is a too lean condition that is seen most often.
In a too lean backfire, there is a cycle where the lean mixture didn't get ignited, and goes out the exhaust valve into the hot exhaust pipe, where it then ignites. This makes a big "pop" in the exhaust pipe that can be very loud.

I have never seen any damage from this. But it is an indicator that the mixture is not correct for the closed-throttle position.

[mattsz]

Thanks ACE!

I thought this silencer was made to work with the EFI engine - and perhaps it IS working as designed.

For the moment I'll ride it and see what happens.  But if the EFI doesn't sort the mixture out, should I try something? 

[ace.cafe]

Thanks ACE!

I thought this silencer was made to work with the EFI engine - and perhaps it IS working as designed.

For the moment I'll ride it and see what happens.  But if the EFI doesn't sort the mixture out, should I try something?

It is very common for a free-flowing exhaust system to require some attention to the fuel/air mixture. Generally, a free-flow system has the effects of leaning out the running of the bike, because better cylinder scavenging takes place. Some EFI systems have enough flexibility to deal with this change, and some don't. Some might need adjustment.
Adjusting the TPS closer to 0.7v output seems to help some people, from what I have read. Don't go all the way up to 0.7v, though. That's the maximum. You might need to try just a little higher than you have, and then see how that is, and make a judgment about whether it needs more, or not. It's a trial-and-error process to get it right where you want it.

This is a process that we do with carburetors all the time, when a free-flow system is installed. Except that we re-jet the carb to get it where we want it. If we don't, then it pops out the exhaust like yours is doing.

[mattsz]

Ok, thanks.  I'm out for a longer ride today.  I'll watch it and see what happens.  As I understand things, too rich is troublesome, but too lean is definitely bad.  As long as I'm not doing any damage...

[ace.cafe]

Ok, thanks.  I'm out for a longer ride today.  I'll watch it and see what happens.  As I understand things, too rich is troublesome, but too lean is definitely bad.  As long as I'm not doing any damage...

The backfiring might not be causing any damage, but the lean condition MIGHT be able to cause some damage. So, it needs to be made correct, if the EFI cannot adapt to it.

[JVS]

Great advice from ace.cafe as usual. I will tell you my side of things.

When I installed my EFI silencer from Hitchcocks, I had a very similar story such as yourself. Had a few backfires just after the installation..that is I went for a quick ride and had pops whilst I accelerated quickly on purpose and let the throttle off. I guess the ECU needs a bit more than 5 minutes to adjust..or maybe it just depends on the oxygen sensor.

With any aftermarket silencer on our EFI bikes, you will always have some backfiring on certain occasions. Give it a few more days and see how it is. It's just just you getting used to the new loud  sound and your B5 getting accustomed to it also.

I had gone down the TPS lane and had altered the voltage to make it a tad richer. There was not a lot of difference. So after a week or so, I had returned to my original TPS idle voltage. My B5 doesn't backfire often now. The system is used to the silencer. I have checked the spark plug on numerous occasions with the EFI silencer and it is running at optimum mixture. (Nice brownish/tan spark plug electrode ~ 0.7mm gap) I am sure your RE wouldn't backfire as much after a few days of riding. If it persists, then let us know.
 
For the past 2000 miles or so I've been running without the mechanical baffle. It runs decent. Very rare backfiring. Nothing to be worried about. It's just some fun! A loud pop here and there is good for the cagers and pedestrians alike. Brings a smile to my face sometimes haha.

[barenekd]

Mine did the big bang occasionally, no damage, no problem. It did serve as a great deterrent for me one day, though. A guy pulled out in front of me turning right on red, and as I pulled up next to him, I kinda gave him the evil eye and he was just staying alongside as a kind of aggressive move. My EFI let out one of those famous bangs, and, man, did that guy back off! The timing couldn't have been better! I think he thought I took a potshot at him. Any way he didn't stick around me any more!
Bare

[TWinOKC]

I have the EFI silencer also.  When I first fitted it the thing would backfire quite often, usually when the outside temp was a little cool like in the 40's.  I liked the backfiring but now it seems to have calmed down (computer self adjusted) very seldom get any good bangs.  I really miss the backfiring, like others have said, it keeps those cagers off your ass.

[Royalista]

Mine did the big bang occasionally, no damage, no problem. It did serve as a great deterrent for me one day, though. A guy pulled out in front of me turning right on red, and as I pulled up next to him, I kinda gave him the evil eye and he was just staying alongside as a kind of aggressive move. My EFI let out one of those famous bangs, and, man, did that guy back off! The timing couldn't have been better! I think he thought I took a potshot at him. Any way he didn't stick around me any more!
Bare

Bullet as guardian angel.   I like it.    A lot.

[mattsz]

Went for a 160 mile ride today.  The bike performed well, only backfiring three or so times, and nothing as loud as that gunshot report the other day.  I also got unusually good economy, 71 MPG on that tankful.    Wonder why?

That silencer is loud, though - probably too loud for my liking...

[Boots]

Gotta admit I love my NField Gear EFI silencer - performance is improved, it looks the part and the sound is really something special. I plan to run it until it falls off (heaven forbid) and becomes bluish gold.

[JVS]

Went for a 160 mile ride today.  The bike performed well, only backfiring three or so times, and nothing as loud as that gunshot report the other day.  I also got unusually good economy, 71 MPG on that tankful.    Wonder why?

That silencer is loud, though - probably too loud for my liking...

Awesome stuff. That silencer does seem loud when you are new to it. Trust me, after a few more rides you will get used to it. I'm riding without the baffle and now I'm used to the even louder sound. Doesn't seem bad to me anymore. You can try earplugs.

However, for me personally, earplugs feel like they disconnect me from the surroundings and reduce your overall awareness of people/cagers around. Those little sounds/noises matter. Keeps you alert and you can hear any other vehicles when they come close to you etc. Even if you scan your mirrors every few seconds whilst riding, there are some idiots who tend to come up on your backside as fast as they can and then try to overtake you etc. 1 second there is nothing behind you, and the other you see a big 4x4 O_O

According to your fuely thing, 71mpg has been the best performance of your B5 till now. It is easily capable of 75mpg+. Enjoy.

[singhg5]

That silencer does seem loud when you are new to it. Trust me, after a few more rides you will get used to it. I'm riding without the baffle and now I'm used to the even louder sound. Doesn't seem bad to me anymore.

Watch out JVS if it does not seem bad !

From another perspective, you don't want a hearing aid in your mid 20's or  mid 30's.  Hardly anyone thinks about it until it is too late.

Ear plugs are not for me during motorcycle riding. Hate the ear pressure changes and feeling of something in ear canal. I like to hear and see everything around me.

Occasionally used them during flying, these specially designed Ear Planes which have a hole inside to balance air pressure inside out.

[JVS]

Singh Ji,

I agree with you. Our helmets (mine at least), muffles the excessive sound of the silencer and other ambient noises. However, the main factor that degrades our hearing is the wind noise. Excessive wind noise is the culprit for lowered hearing and possible tinnitus in motorcycle riders.

For local town and suburban riding, I do not use earplugs. However, the wind noise gets quite bad for me on longer trips where the speed is around or greater than 50mph. Wind noise levels over 50dB in our helmets can be bad. There is a chart on some website showing how much volume our ear drums can handle fine for a certain period before it starts to hamper the hearing. In these longer trips I do try to use the earplugs.

[mattsz]

...You can try earplugs.

I WAS wearing earplugs!  I generally don't wear them on my 12 minute ride to work, but I always do on any longer rides.  It was against the wind noise, now it will clearly by against the wind and the bike noise.  I have pretty sensitive ears, and I want to keep them working well as long as I can.

I once worked for a year on a small industrial beach-landing ferry, transporting mostly trucks and equipment to islands that have no vehicular access.  The truck drivers always wanted to see the engine room.  I would bring them down and offer them ear protection, and about half the time they refused it - the primary reason was, "It's ok, I'm used to the noise."  This was a seriously loud engine room environment - we ran twin 12-cylinder Detroit Diesel mains.  Well, I would argue that it wasn't that these guys were "used to" the noise, but that their hearing was already shot.

According to your fuely thing, 71mpg has been the best performance of your B5 till now. It is easily capable of 75mpg+. Enjoy.

Easily capable?  Maybe, but I haven't gotten near it until this last tank.  And while I'm at it, I need to figure out why Fuelly says my average MPG is lower than my worst number.  Maybe those two "partial fill-ups" are skewing my results?