backfire (popping) on decel....what's that mean? - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
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post #1 of 21 Old 04-05-2008, 10:54 PM Thread Starter
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Question backfire (popping) on decel....what's that mean?

Just picked up an '03 Vee 3 weeks ago with only 3,300 miles on it. It has Two Brothers Titanium pipes and a PCIII. I just returned from a 300 mile ride to Condon and back and notice that if I was running above 4200 RPM and let completely off the throttle it would backfire (or pop) out the exhaust. It would do this at 4200 RPM consistently. I could rev up to 6000 and then let off the throttle and at 4200 I would hear it.
Am I running to lean in that range or to rich? The bike runs great and I have no issues with the power delivery. My mileage stayed at 38mpg the entire day.

Any input would be nice. I can adjust the map but I am not sure what this "symptom" calls for exactly. Thanks - Chris

NOTE: I am running the M311-003 map.

[B][I][SIZE=3] Ride Safe, Ride Often [/SIZE][/I][/B]
[B]'03 Vstrom - 996 - [I](3,318 miles and counting)[/I][/B]
OEM luggage, Zero Gravity windscreen, Two Brothers Titanium exhaust, PCIII
[B]'05 Vstrom[/B] [B]- 996 -[/B] [I][U](death by rock)[/U][/I]
Suzuki heated Grips, Suzuki centerstand, PCIII
[B]'83 Honda Shadow 750[/B] [I][U](sold)[/U][/I]

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post #2 of 21 Old 04-05-2008, 11:12 PM
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You're talking about what many refer to as afterfire which is commonly referred to as backfire. Fuel not being burned in the combustion chamber is exhausted into the pipes where the next exhaust stroke ignites it. That's normally a sign of a lean condition from when a mixture is too lean to ignite. Too rich to burn would be very unusual. I would like to see backfire reserved for the ignition of fuel in the intake tract .
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Nicknames I use to lessen typing, Vee = 2002-2012 DL1000s. Vee2=2014-2016 DL1000s. Wee = 2004-2011 DL650s. Glee = 2012-2016 DL650s
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post #3 of 21 Old 04-06-2008, 01:38 AM Thread Starter
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Thanks GW. I've never heard the term "afterfire". I'll look into making adjustments to my map.
-Chris

[B][I][SIZE=3] Ride Safe, Ride Often [/SIZE][/I][/B]
[B]'03 Vstrom - 996 - [I](3,318 miles and counting)[/I][/B]
OEM luggage, Zero Gravity windscreen, Two Brothers Titanium exhaust, PCIII
[B]'05 Vstrom[/B] [B]- 996 -[/B] [I][U](death by rock)[/U][/I]
Suzuki heated Grips, Suzuki centerstand, PCIII
[B]'83 Honda Shadow 750[/B] [I][U](sold)[/U][/I]

"Only two defining forces have ever offered to die for you: 1. Jesus Christ. 2. The American G.I.
One died for your soul, the other for your freedom."
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post #4 of 21 Old 04-08-2008, 05:14 PM Thread Starter
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Update:

Thanks again for you input GW. I made some adjustments to my PCIII and the problem has gone. I didn't know that this condition was called an "afterfire". Well, you learn something new every day. Thanks again :rolleyes:

-Chris

[B][I][SIZE=3] Ride Safe, Ride Often [/SIZE][/I][/B]
[B]'03 Vstrom - 996 - [I](3,318 miles and counting)[/I][/B]
OEM luggage, Zero Gravity windscreen, Two Brothers Titanium exhaust, PCIII
[B]'05 Vstrom[/B] [B]- 996 -[/B] [I][U](death by rock)[/U][/I]
Suzuki heated Grips, Suzuki centerstand, PCIII
[B]'83 Honda Shadow 750[/B] [I][U](sold)[/U][/I]

"Only two defining forces have ever offered to die for you: 1. Jesus Christ. 2. The American G.I.
One died for your soul, the other for your freedom."
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post #5 of 21 Old 04-08-2008, 05:34 PM
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"Afterfire" is just beginning to catch on as a term to differentiate an out of the combustion chamber fire that goes back along the mixture path from an an out of the combustion chamber fire that occurs in the mixture path after normal combustion.

Pat- 2007 DL650A was ridden to all 48 contiguous states. I didn't quite make it to 17,000 miles on the 2012 DL650A.
Nicknames I use to lessen typing, Vee = 2002-2012 DL1000s. Vee2=2014-2016 DL1000s. Wee = 2004-2011 DL650s. Glee = 2012-2016 DL650s
See https://www.stromtrooper.com/general-...nicknames.html

Please vote in the poll on what Strom(s) you have at https://www.stromtrooper.com/informat...-you-have.html
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post #6 of 21 Old 04-08-2008, 05:56 PM
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exhaust leak

a leak where the head pipe joins the muffler can cause back fires

swann strom
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post #7 of 21 Old 04-09-2008, 03:56 PM
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Quote:
Originally Posted by Criscokid View Post
Thanks again for you input GW. I made some adjustments to my PCIII and the problem has gone. I didn't know that this condition was called an "afterfire". Well, you learn something new every day. Thanks again :rolleyes:

-Chris
Chris,
How much fuel did you add and I assume you added it at 0 and 2% from idle to 4200 rpm or just at 0% throttle opening??

Rich

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post #8 of 21 Old 04-10-2008, 10:46 PM
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post #9 of 21 Old 04-11-2008, 11:33 PM Thread Starter
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Quote:
Originally Posted by PackMule View Post
Chris,
How much fuel did you add and I assume you added it at 0 and 2% from idle to 4200 rpm or just at 0% throttle opening??

Rich
Yes, I did. But it didn't completely fix the issue as I found out a day or so later. I decided to start over. But instead of going back to the M311-003 map I dumped in the M311-002 map. This map is much leaner than the 003 and it is for an '02 with TwoBrothers slipons (which is what I have). I rode home today and the air temp was about 64F. I noticed the surging at 3,800-4,200rpm. Then I ran the RPM's up to 6,000 and let off. Sure enough it sounded like firecrackers going off behind me :rolleyes:. So I've started adding some fuel. I will continue to add small amount until I have cured or somewhat cured this issue. Fuel economy is a must so I might have to put up with some of the popping to maintain mileage.
On another note, I have not done a TBS (sorry BigB ) so that could be some of it (if not all). I haven't had alot of time to play with this. The FI mapping seems to be different on this bike compared to my '05.
Thanks for the input everyone :-D.
-Chris

[B][I][SIZE=3] Ride Safe, Ride Often [/SIZE][/I][/B]
[B]'03 Vstrom - 996 - [I](3,318 miles and counting)[/I][/B]
OEM luggage, Zero Gravity windscreen, Two Brothers Titanium exhaust, PCIII
[B]'05 Vstrom[/B] [B]- 996 -[/B] [I][U](death by rock)[/U][/I]
Suzuki heated Grips, Suzuki centerstand, PCIII
[B]'83 Honda Shadow 750[/B] [I][U](sold)[/U][/I]

"Only two defining forces have ever offered to die for you: 1. Jesus Christ. 2. The American G.I.
One died for your soul, the other for your freedom."

Last edited by Criscokid; 04-11-2008 at 11:36 PM. Reason: not telling
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post #10 of 21 Old 04-12-2008, 09:31 AM
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As was said earlier, check all the joints where you added the exhaust. Use some exhaust sealer before you chase this to far. A little leak sucking air can cause the after-fire.

It's more fun to ride a slow bike fast than to ride a fast bike slow.
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