backfiring when engine braking

[aapasquale]

I have a 1994 R1100RS with 36,000 miles which is a beauty-about a month ago I removed the old silencer with catalytic converter because the inner pipe had corroded and fallen off inside and had gotten a little loud-I got a used one one from one of our members from the southwest for a song-turned out to be pristine-I removed the oxygen sensor from the old muffler and put it into the replacement-installed new muffler and alls good.....however, I'm noticing when I use the engine for braking, it backfires when it did not before-also, the mileage is down 6-8 miles per gallon-

does the Motronic unit need to be reset after this type of repair? Is it possible to reset by just pulling the fuse for it? Is it likely the old O2 sensor has a hand in this? Any thoughts would be much appreciated
Thanks,
Tony

 

[rdhudson]

Pull it!

That is one beautiful bike!
I am new to R1100's so I don't know if it is necessary in your case but I have had to reset the Motronic on my 1998 R1100R (fuse 5 on mine) It does relearn the whole FI map in 20 miles or so. However it runs like crap as it begins. Let it idle for a couple of minutes then ride at constant rpms for part of a minute in stages up the range to let the feedback teach the computer what is right. Once the system knows what is a good mixture at many speeds acceleration and drivability are restored. In my bike's case a skipping, hesitating, and balky runner became a smooth, powerful ride with good response and great full throttle fun.
Ralph

 

[bikerfish1100]

your easier reset is to turn key to on position, twist throttle full on 2 or 3x, then start the bike as normal. should work fine, with no obnoxious running for 20+ miles (it did when I changed my Motronic's FI chip to a Laser).

backfiring like that is usually caused by a somewhat lean condition- any other changes you made that could be effecting it?. could be that the O2 sensor is not working properly.

 

[kgadley01]

I used the #5 fuse removel and remap method to stop my R1100RT from surging.

 

[bikerfish1100]

pulling the fuse (relay) to deal with surging is a different situation than resetting the Motronic to deal with backfiring.
however, if the bike is backfiring and surging (both can be lean conditions, altho backfiring can also be from too rich), then that could be a helpful fix.

 

[aapasquale]

backfiring like that is usually caused by a somewhat lean condition- any other changes you made that could be effecting it?. could be that the O2 sensor is not working properly.

I made no other changes at all--Is there a way to test the O2 sensor to see if it is behaving properly?

Thanks, Tony

 

[ANDYVH]

Its not "backfiring" at all. Its a lean fuel condition very common om modern bikes when the throttle is closed during decel with the clutch out. Test it next time, when it happens, pull in the clutch and the "popping" stops immediatelty, proving it is not backfiring.

True backfiring is a timing condition where the ignition actually fires when the intake valves are slightly open and the ignited fuel/air mix actually "backfires" out the intake. VERY rare with modern engines and electronic ignitions.

What your RS, like my RS, is doing is "exhaust popping". Totally normal and in no way damaging to the bike. It is not backfiring and a lot of people mistakenly describe it as a condition which it is not. Some people even try to claim it as a warranty issue and some dealers don't even know that it is not backfiring. Exhaust popping is only correctable by making the fuel/air mix MORE rich.

On my bike I installed a Techlusion system to richen the fuel to air mix and the popping stopped entirely. And,...my fuel mileage went down to the high 30's. I adjusted the Techlusion to run more lean, and my fuel mielage went up and the popping returned. Either accept as a normal condition of lean burn engines, or simply pull in the clutch, or install a Fuel Booster Plug or Techlusion device. Oh, and installing a modified exahust only makes the popping worse because it further leans out the fuel/air mix.

Backfiring caused by being too rich a fuel/air mix? I doubt it, if the valve timing is right. It would have to be REALLY rich to cause a real backfiring. And by then the plugs would be so fouled the bike probably wouldn't run.

 

[roborider]

You can also get exhaust popping from a leak in the exhaust. Feel around all the connections, from header to muffler, and be sure you don't have a loose fitting or rust hole that is allowing outside air to get in.

 

[awagnon]

you can also get exhaust popping from a leak in the exhaust. Feel around all the connections, from header to muffler, and be sure you don't have a loose fitting or rust hole that is allowing outside air to get in.

+1 I agree with Rob.

 

[aapasquale]

You can also get exhaust popping from a leak in the exhaust. Feel around all the connections, from header to muffler, and be sure you don't have a loose fitting or rust hole that is allowing outside air to get in.

the old muffler did not produce the "popping"--also, my mileage previously was in the high 40's to 50 mpg--I will test for leaks tomorrow--thanks! Tony

 

[Gary98]

My bike always pops when letting off the gas. It is the worst right after a service. They just set these things so lean.

 

[PGlaves]

I think the popping comes from an exhaust leak. I don't have a good explanation for a drastic mileage drop unless the cat-con on the new system is clogged.

 

[flars]

pop

"...your easier reset is to turn key to on position, twist throttle full on 2 or 3x, then start the bike as normal..."
Only valid on the 1150.

Like others have said - sounds like an air leak between the new muffler and the old parts.

 

[bikerfish1100]

"...your easier reset is to turn key to on position, twist throttle full on 2 or 3x, then start the bike as normal..."
Only valid on the 1150.

Like others have said - sounds like an air leak between the new muffler and the old parts.

really? it worked perfectly fine on my R1100S ....... just sayin'.

 

[m_stock10506]

really? it worked perfectly fine on my R1100S ....... just sayin'.

Oh Boy! So many bits of info flying around in this thread that I believe are wrong.

The OP is asking about his bike, an R1100RS. The R1100 bikes have the Motronic 2.2 version. This version uses the TPS on the side of the left throttle body to set the voltage for the throttle position. The 2.2 Motronic doesn't learn from riding and it doesn't learn from moving the throttle from closed to wide open after pulling the fuse. Pulling the fuse doesn't reset the 2.2 Motronic.

The R1100S doesn't have the 2.2 Motronic, it's got the 2.4 Motronic, same as the 1150 bikes. The 2.4 Motronic is the one that can have the fuse pulled to reset the Motronic and the 2.4 learns the throttle positions.

If this is wrong, somebody will correct me....

 

[lkchris]

I think the popping comes from an exhaust leak. I don't have a good explanation for a drastic mileage drop unless the cat-con on the new system is clogged.

Pay most attention to this post.

The exhaust system is the only thing changed.

The leak introduces extra oxygen, which facilitates combustion of raw fuel in the exhaust system.

 

[roger 04 rt]

Pull fuse 5 for a minute to reset the Motronic. Then ride at a steady speed at as many RPMs in the cruising range as you comfortably can so that your Motronic can relearn your engine.

What I am guessing happened is that while you rode with your old, worn out muffler, your engine was able to flow more air and your Motronic adapted by adding some fuel to get to its correct air-fuel ratio.

Then you put on the replacement working muffler and the airflow went back to normal but the fueling by the Motronic hasn't gotten used to it. By resetting, the Motronic will start over and learn the correct amount of fuel again.

Good luck, let us know how it works out.

 

[jammess]

Oh Boy! So many bits of info flying around in this thread that I believe are wrong.

The OP is asking about his bike, an R1100RS. The R1100 bikes have the Motronic 2.2 version. This version uses the TPS on the side of the left throttle body to set the voltage for the throttle position. The 2.2 Motronic doesn't learn from riding and it doesn't learn from moving the throttle from closed to wide open after pulling the fuse. Pulling the fuse doesn't reset the 2.2 Motronic.

The R1100S doesn't have the 2.2 Motronic, it's got the 2.4 Motronic, same as the 1150 bikes. The 2.4 Motronic is the one that can have the fuse pulled to reset the Motronic and the 2.4 learns the throttle positions.

If this is wrong, somebody will correct me....

The 1994 R1100S & RS both have a Motronic 2.2 according to RealOEM.com and I question their learning ability.

 

[PGlaves]

The 1994 R1100S & RS both have a Motronic 2.2 according to RealOEM.com and I question their learning ability.

There is no such thing as a 1994 R1100S. Introduced in 1999 I believe. The R1100RS was introduced in 1993 as a 1994 model. They don't learn in the sense that the later Motronic devices do. I don't believe this has anything to do with fuses, or twisting throttles, or riding for 20 miles.

 

[aapasquale]

I changed the battery today--the one on the bike literally died this morning (after a long and painfully slow downward spiral)--had ordered one by Odyssey last week in anticipation of it's demise--when I changed the battery I, of course, disconnected the battery--upon installing new the battery, I switched key to on and twisted throttle a couple of times to set TPS--started and ran like a charm--"pop" is still there--tomorrow I will start it on the center stand and check all the muffler connections to make sure I assembled it properly--will let everyone know if anything changes

Appreciate all the feedback on this--love this bike

Tony